9. TIME DOMAIN INDUCED POLARIZATION PROGRAM (TDIP)

Transcription

1 9. TIME DOMAIN INDUCED POLARIZATION PROGRAM (TDIP) 9.1 INTRODUCTION FIXED FUNCTION KEYS TDIP PROGRAM OPERATION... 5 MAIN DISPLAY:...5 HEADER...7 FOOTER...8 LINE SETUP...8 ACQUISITION CONFIGURATION...10 CHANNEL TABLE...12 SOFT FUNCTION KEYS...13 ARCHIVE SUBMENU...14 SCREEN: CHANNEL TABLE DISPLAY SCREENS...15 SCREEN: SETUP...15 SCREEN: GAIN/CRES...17 SCREEN: RESULTS...18 SCREEN: STACKS...19 SCREEN: XYZ EDIT...20 JOB_INFO SUBMENU...22 RESET FUNCTIONS...23 SCOPE FUNCTION BOARD CALIBRATION SUBMENU GATHERING DATA PROGRAM START UP...31 DATA ACQUISITION...31 STOP ACQUISITION...32 ACQUISITION ERRORS VIEWING DATA CACHE FILE A NOTE ON AUTOMATIC LOCATION UPDATES RST_OFSET EXAMPLE...42 RST_N-SPC EXAMPLE A NOTE ON SCALING ALGORITHMS TIME DOMAIN WINDOW TIMING INFORMATION...56 GDP October 2014

2 GDP INSTRUCTION MANUAL 9.11 SAMPLE MENUS FOR "LABROX" ARRAY NOTES ON FIELD CONFIGURATIONS FIELD CONFIGURATIONS GDP AS TRANSMITTER CONTROLLER WITH REFERENCE RECORDING...59 GDP SETUP FOR RESISTIVITY, TDIP, RPIP, NRCR...62 GDP SETUP WITH ROLL-ALONG CABLE: RESISTIVITY, TDIP, RPIP, NRCR...63 TRANSMITTER SETUP: TDIP, RPIP, NRCR...64 TRANSMITTER SETUP WITH CURRENT REFERENCE...65 RECEIVER SETUP WITH CURRENT REFERENCE...66 LABORATORY ROCK MEASUREMENT SETUP...67 ALTERNATE LABORATORY ROCK MEASUREMENT SETUP...68 GDP Section 9, Page 2 October 2014

3 9.1 INTRODUCTION TIME DOMAIN INDUCED POLARIZATION PROGRAM This Time Domain Induced Polarization (TDIP) program uses standard phase-lock stacking and averaging for field and laboratory multifrequency IP measurements. This is an enhanced program using synchronous stacking and averaging to improve the signal to noise ratio. The frequency range of the TDIP program is from to 32 Hz. TDIP measurements are commonly made using the fundamental frequencies of 0.125, 1.0, and 8 Hz. Available channel designations include: Ex, Ey, Ez, and Ref (for current referenced TDIP). New to the GDP-32 24, the electrode locations can now be described in 3 dimensions, simplifying the description of special case field conditions, and improving the calculation of apparent resistivity for those conditions. X Station distance along line. Y Station distance across line. Z Station distance below surface. Apparent Resistivity (Rho) calculations, both in the GDP and in Post Processing, use a general equation based on the transmitter and receiver electrode locations, and are no longer based on N-values. This general equation for Rho is used for all ARRAY types except for laboratory rock measurements. N-values are used only to help operators accustomed to the GDP-32 II, in entering and verifying the values that describe the actual survey setup. Electrode Offset distance from the receiver, new to the CR and TDIP programs for the GDP-32 24, can also be used to describe the survey setup. Use of Offset can simplify data entry when moving transmitter electrodes or the receiver, especially for operators new to geophysical surveying. The standard board calibrate buffer is saved as 24BOARD.CAL on the GDP C:\ drive. Board calibration data can be viewed in the Calibration submenu of the TDIP program. If no calibrate files are found, empty files are created and factors of 1.0 mag and 0.0 phase are assumed. SELECT UP SELECT DN Home End All selectable fields can be modified using and. Numeric fields can be incremented or decremented using the same keys. Some numeric fields, such as Gain/Atn can only be modified to allowable values by using these keys. Pressing quickly moves the cursor around the various areas of interest for the main menu screen and some submenus in all programs. Section 6 describes calibration, synchronization and generic program operation. At the end of this TDIP program manual are several setup diagrams for field measurements. Note: Some numeric or alphanumeric values are not registered in the GDP memory until you PREV FIELD NEXT FIELD Pg Up Pg Dn Enter exit the parameter field by pressing,, or. Exceptions are the frequency and the powerline notch filters. Whenever the frequency is changed, the sample rate is automatically changed through the timing card, but the anti-alias filter is not changed until just Enter prior to data acquisition. Pressing to gather data, the receiver will automatically set the anti-alias filter as defined by internal look-up tables. October 2014 Section 9, Page 3 GDP-32 24

4 9.2 FIXED FUNCTION KEYS GDP INSTRUCTION MANUAL Six fixed function keys are located below the six soft function keys ( through ) at the bottom edge of the LCD. Enter the cache viewer. Data can be viewed as time-series or apparent resistivity plots vs. frequency. Exits the TDIP program and return to the main menu for selection of other data acquisition programs. The key can also be used to exit submenus of the program. Enter the calibrate and system checking submenu. See the Calibrate section of this manual as well as GDP Section 6.1, Calibration for more details. Perform a one-time gaining of the channels that are currently On and for the current selected frequency (FREQ). (This key has no function in older versions of this program.) Perform a one-time buck out of any self-potential (SP) or amplifier offset, for all the channels that are currently On. (This key has no function in older versions of this program.) Measure the contact resistance or coil output resistance. See GDP Section 6.3, Measuring Contact Resistance for more details. GDP Section 9, Page 4 October 2014

5 TIME DOMAIN INDUCED POLARIZATION PROGRAM 9.3 TDIP PROGRAM OPERATION One of the differences between the GDP and its predecessor the GDP-32 II is that there is no longer a menu structure at the start of each acquisition program. Each program will now start in the main user interface menu. There are submenus that the operator may use to enter program specific entries. These submenus vary between the different programs. Instead of cumbersome menu levels which force a sequence of data entry, the operator can use the following guideline: 1. Start by filling in the parameters in the JOB_INFO submenu. 2. Back on the Main Menu, set ARRAY type, A-SPACE, S_SPACE and other Line Setup parameters. Press, RST_TX, to initialize default values based on these settings. 3. Configure the channels in the Channel Table using, RST_OFSET or RST_N- SPC, to configure automatic location updates for the survey. 4. Set Acquisition Configuration parameters. 5. Acquire data. 6. Review the data, and finally, 7. Archive the data cache file. These steps are all accessed from the Main Menu, and its various screens and submenus, as described in this manual. Note: The order of these steps is not required, however due to some features of the program, changing some fields can cause other fields to be updated. This can cause some values, particularly in the Channel Table, to be modified after the user has already set them. MAIN DISPLAY: The screen provides 80 characters on 30 lines. The entire screen is visible on the Color display. However, 60 characters on 20 lines are visible on the Monochrome display. Use the and one of the quadrant keys to shift the display to another area: + SELECT UP PREV FIELD Home Pg Up key SELECT DN End NEXT FIELD Pg Dn SELECT DN SELECT UP End Home For example, shift the display down by using, and back up with. Only the first diagram below shows the entire screen. MOST OF THE OTHER SCREENS IN THIS MANUAL DISPLAY ONLY 60 characters BY 20 lines. The TDIP Main Menu has three areas for data entry: Line Setup, Acquisition Configuration, and the Channel Table. A Header line shows current conditions and a Footer area shows status and messages. Below this, the lower left screen shift area holds historical Error and Warning October 2014 Section 9, Page 5 GDP-32 24

6 GDP INSTRUCTION MANUAL messages. These are generally common with all the GDP programs. The cursor directly to some of the main input areas of the display. key moves the <0903a_24TDIP_MainAreas> Full display screen showing defined areas. GDP Section 9, Page 6 October 2014

7 TIME DOMAIN INDUCED POLARIZATION PROGRAM <0903a_24TDIP_MainAreas> Display showing 60 characters and 20 lines. (the colors are for this illustration only) AREAS COMMON TO ALL PROGRAMS HEADER The Header line contains the following information: 0 Block number. TDIP_1.37j Program name and version. BAT 14.3 Battery Level in Volts. Sats 0 Number of GPS satellites (when GPS sync option is available). 21 Jul 2014 Date. 14:28:46 Time (Hours Minutes, Seconds). October 2014 Section 9, Page 7 GDP-32 24

8 FOOTER GDP INSTRUCTION MANUAL The Footer area contains several lines of information: The STATUS: line Indicates the general status of the program or progress during data acquisition. Below this is a Help line that displays warnings, acquisition progress steps, and requests operator confirmation or input. The third line acts as labels for the soft function keys. These labels change depending on the SCREEN and field that the cursor is in. The last ten lines of the display are a history of messages, not generally visible in the small LCD screens unless it is shifted by pressing the start of each new acquisition period. LINE SETUP. These historical messages are cleared at The Line Setup area of the screen should be filled in before setting parameters in the Channel Table. The information in this part of the screen can have an affect on how changes to other fields are automatically updated, especially in the Channel Table. Many of these input fields are seldom changed after a survey has started, therefore they are located in the lower half of the screen. Though there is no required sequence for editing the input fields, it is suggested that these fields be entered first. The following list of input fields is in the suggested order of data entry. TIME SERIES This setting determines if all the raw A-D readings should be written to the cache as a time series, Yes or No. Writing the time series to the cache significantly increases the size of the cache file. This option is set to No. for normal operation. It is set to Yes for enhanced Post Processing, for analyzing input signals or other diagnostic purposes. Note: The GDP always collects the time series, a continuous stream of A-D readings for all of the cycles, into a memory buffer for processing, regardless of this setting. Home End ARRAY Seven types of arrays are selectable with the or keys: D-D Dipole-Dipole P-D Pole-Dipole P-P Pole-Pole Sch Schlumberger Grd Gradient D-H Downhole LAB Core Sample Note: Different ARRAY types can require different Line Setup information, therefore as the ARRAY type is changed, the input fields will change according to the type selected. TX STN A-SPACE SELECT DN Informational, transmitter location identifier. End SELECT UP SELECT DN E-field dipole size in meters or feet (a-spacing). Notice that entering a value in this field causes all the values in the Length column of Channel Table, to be modified to match. Variable a-spacing can later be configured by GDP Section 9, Page 8 October 2014

9 Ft / M S-SPACE TIME DOMAIN INDUCED POLARIZATION PROGRAM modifying values in the Length column of the Channel Table as discussed later in this manual. Specifies units of length, Feet or Meters, for all length and space entries. Station number space, or S-space (stn#), is a unit dipole length in whatever units are to be used for TX and RX locations. This allows correct calculation of apparent resistivity, Rho, when station numbers are not scaled to feet or meters. A dipole's length can be calculated by the formula: Length = (RX2 RX1) * Aspace / Sspace Note: ALL electrode locations for the transmitter TX, and receiver RX, must be entered in S- space units. The Length displayed in the Channel Table will be in feet or meters for verification. LINE Informative user defined alphanumeric identification that may be used in post processing. Direction Informative selection for line direction. Selections are: N, NE, E, SE, S, SW, W, NW, DH (drill hole), SET (any user defined set). X-AZ Informative azimuth of the X direction of the line (0 to +/-360). SPREAD TX: AX TX: AY TX: AZ Informative 2-character user defined identification. Location, along line (X) of the lowest numbered electrode of the transmitter dipole. The field for AX designation is NNNNNNN with a floating decimal point. Location, grid line or across line distance (Y) of the lowest numbered electrode of the transmitter dipole. The field for AY designation is NNNNNNN with a floating decimal point. Depth below surface (Z) of the lowest numbered electrode of the transmitter dipole. The field for AZ designation is NNNNNNN with a floating decimal point. Note: The AZ field is only visible in the XYZ EDIT screen, but is always used in Rho calculations. TX: BX TX: BY TX: BZ Location, along line (X) of the highest numbered electrode of the transmitter dipole. The field for BX designation is NNNNNNN with a floating decimal point. Location, grid line or across line distance (Y) of the highest numbered electrode of the transmitter dipole. The field for BY designation is NNNNNNN with a floating decimal point. Depth below surface (Z) of the highest numbered electrode of the transmitter dipole. The field for BZ designation is NNNNNNN with a floating decimal point. Note: The BZ field is only visible in the XYZ EDIT screen, but is always used in Rho calculations. October 2014 Section 9, Page 9 GDP-32 24

10 GDP INSTRUCTION MANUAL RX0: RX Reference location, along line (X) of the receiver. The field for RX designation is NNNNNNN with a floating decimal point. Note: Positive channel electrode locations, RX1, are calculated as: RX1 = RX0:RX + Offset. RX0: RY RX0: RZ Reference location, grid line or across line distance (Y) of the receiver. The field for RY designation is NNNNNNN with a floating decimal point. Reference depth below surface (Z) of the highest numbered electrode of the transmitter dipole. The field for RZ designation is NNNNNNN with a floating decimal point. Note: The RZ field is only visible in the XYZ EDIT screen. Note: The TX: AX, AY, AZ, BX, BY, and BZ,locations are always used in Rho calculations. They are also used to calculate RX1 and RX2 locations from N values, or the reverse. RX0: RX, RY and RZ, are not use in Rho calculations. They are used to calculate RX1 and RX2 locations from Offsets, or the reverse. Note: Changes to any of the TX: and RX0 fields will cause RX1, RY1, RZ1, RX2, RY2 and RZ2 values in the Channel Table to be automatically updated. This feature is explained in more detail later in this manual. SAMPLE ID Informative field used for Lab Rocks testing (ARRAY Lab). SAMPLE LEN The axial length of a rock specimen, in centimeters, for calculating resistivity, used for Lab Rocks testing (ARRAY Lab). SAMPLE AREA The cross sectional area of a rock specimen, in centimeters squared, for calculating resistivity, used for Lab Rocks testing (ARRAY Lab). The fields visible in the Line Setup area of the screen change in response to the ARRAY type selection. ACQUISITION CONFIGURATION The Acquisition Configuration area of the screen contains the following fields: FREQ CYCL This selects the frequency to analyze. The selections increment in binary steps from to 32 Hz. When the CYCL count is a binary value, adjusting the FREQ field up or down causes the cycles to automatically change by the same factor. When CYCL is set to a non-binary value it remains constant while the frequency is changed. This field specifies the number of cycles to average. All data points will be read in a continuous series without breaks. This value can be modified SELECT UP SELECT DN Home End directly to any value, or the and keys can be used to select values from 1 up 16,384 in binary steps. Note: While making selections to the FREQ, and CYCL, settings, the GDP will evaluate the memory and flash disk space required, based on those settings, and number of on channels. If the selected or entered values would cause the collected data to exceed available memory, based on these settings the CYCL value will be reduced to a value that will allow maximum memory GDP Section 9, Page 10 October 2014

11 TIME DOMAIN INDUCED POLARIZATION PROGRAM utilization. An audible warning will be given and the STATUS will indicate: Cycles Reduced, Not To Exceed Memory Limit. Note: This feature can be used to maximize the data collection capability of the GDP. The operator can enter a CYCL value of 99999, and it will be adjusted to the maximum cycles that can be collected in memory. STACKS The total number of time series records specified to be acquired and processed. Each STACK will be recorded in individual blocks in the cache file. Note: If the entered value would cause acquisition memory or flash disk space to be exceeded, the value will be adjusted down in order to have successful data acquisition. The STATUS: field will show a message INSUFFICIENT DISK SPACE for ACQUISITION or INSUFFICIENT MEMORY for ACQUISITION. GAIN ALWAYS ONCE DONE SPONLY MAN Selector for setting the method the GDP will use for setting gain. Options are Automatic gaining, with SP bucking, will occur before each stack. Automatic gaining, with SP bucking, will occur only for the first stack. After the first stack, this option will change to DONE. No gaining will occur on subsequent stacks. Changes to some fields will cause this selection to revert back to ONCE. SP bucking will be performed for all stacks. The gain values currently set in the Channel Table will not be altered. The gain and SP values currently set in the Channel Table will not be altered. Note: On older versions of the Field Survey Program, the Automatic Gain algorithm does not apply an Attenuator setting. It assumes that the operator has set the transmitter to a level that will not require attenuation, relying instead on the increased dynamic range of the 24-bit analog converter. If the incoming signal does however require Attenuation, the MAN or SPONLY modes should be selected for GAIN. The SCOPE function can be used to inspect the incoming signal while making adjustments to the Transmitter Output. NOTCH Powerline notch filter switch. There are several possible selections here, depending upon the hardware configuration of the receiver. OUT All notch filters bypassed and 180 Hz notch filters enabled , 180, 300 and 540 Hz notch filters enabled , 300 and 540 Hz notch filters enabled. Other standard selections are: and 150 Hz notch filters enabled , 150, 250 and 450 Hz notch filters enabled. 50/60 50, 150, 60 and 180 Hz notch filters enabled. October 2014 Section 9, Page 11 GDP-32 24

12 GDP INSTRUCTION MANUAL Note: Powerline notch filters inject some noise into the system, and should only be used when absolutely necessary. More information on Notch Filter design can be found in Chapter 16. SENSE When using the Ref channel, enter the value of the current sense resistor for calculation of the transmitter output current. Values of current sense (shunt) resistors for standard GGT-series transmitters and the laboratory setup are as follows (all values in ohms): or 100m GGT-2.5, GGT or 100m GGT-5, GGT-6, GGT or 50m GGT-20, GGT-25, GGT or 100m ZT-30 / ZT NT-20 1m to 1000K LABROX Note: The SENSE field is not displayed if no Ref component type is defined. Note: If more than one Ref channel is defined, the lowest numbered Ref channel will be used. There is no requirement as to which channel is used. TXCR The Transmitter Current, in amperes. This current is the square-wave equivalent current or what the operator would read off of the transmitter current display. Note: If a Ref component type is defined, the value for this field will be calculated based on the magnitude of the Ref signal and the SENSE resistor value. TIME MEM(mb) CHANNEL TABLE Informational display of the total time required to collect, process and write all of the STACKS to the cache. Informational display of the memory required to collect all the cycles for one stack. The channel table refers to a separate section of the main menu where settings pertaining to a specific channel are made and results for that channel are displayed. The table is a distinct grouping of fields which can be accessed by pressing. There are four SCREEN: selections that configure the Channel Table. Pressing cycles through: SETUP, GAIN/CRES, RESULTS, and STACKS. A fifth screen, XYZ EDIT, can be activated when the cursor is in the Channel Table and the operator presses section on SOFT FUNCTION KEYS for more information.. See the GDP Section 9, Page 12 October 2014

13 SOFT FUNCTION KEYS TIME DOMAIN INDUCED POLARIZATION PROGRAM The function keys through are considered soft function keys because they may perform different functions not only in different programs, but their functionality can change within a program depending on the menu, input field, or Channel Table column the cursor is in. Each key's functionality is identified by its label on the bottom line of the display screen. While the Main Menu is displayed, the keys perform the following functions: ARCHIVE: Start the Archive submenu used to rename the current cache file and initialize a new file. The Archive submenu is described below. SCREEN: JOB_INFO: Cycle through the Channel Table display screens. Job Information submenu used to enter survey job information. Multiple function key based on the current SCREEN and cursor location. For more information, see the section on RESET FUNCTIONS, below. CH_OFF/ON: Toggle channels Off or On. This function is available while the cursor is in the Cmp Typ column of the Channel Table. RST_TX: Reset transmitter and receiver locations. Initialize some features of the CR program based on Line Setup settings. The operator should press this key when finished setting the fields ARRAY, A-SPACE, S-SPACE, TX:AX, TX:AY, RX0:RX and RX0:RY. This function is available in the SETUP screen, and the cursor is not in the Channel Table. RST_OFSET: Re-sequence the Offset for channels above and below the channel row that the cursor is on. This also places the program into the Offset mode for automatically updating electrode locations when RX0 or TX locations are modified. This function is available while the cursor is in the Offset column of the Channel Table. RST_N-SPC: Re-sequence the N-values for channels above and below the channel row that the cursor is on. This also places the program into the N-space mode for automatically updating electrode locations when RX0 or TX locations are modified. This function is available while the cursor is in the N-column of the Channel Table. SCOPE: Real time scope display of a channel's input signal. It functions only when the cursor is in the Channel Table and in the row of a channel that is currently On. Multiple function key based on the current SCREEN and cursor location. EDIT_XYZ: When the cursor is in the Channel Table, this key will enable the XYZ EDIT screen. XYZ_EXIT: When in the XYZ EDIT screen, this will return to the SETUP screen. October 2014 Section 9, Page 13 GDP-32 24

14 GDP INSTRUCTION MANUAL ARCHIVE SUBMENU The Archive submenu, accessed with, allows the user to rename the current cache data file and initialize a new empty file. The renamed cache file is archived to the C:\DATA directory. The screen displays the number of blocks in the current cache file. Only the 8- character file name can be changed. The default name will start with the prefix TDI, followed by 2-character day of the month, then 2-character hour. The last character is sequenced to ensure that a unique name is used. The file extension is always.cac. <0903c_24TDIP_Archive> Enter If the cache archive name is acceptable, press. If there is a name conflict, and error will occur and allow the name to be changed. When successful, the archive name will be displayed to the operator. When finished, press any key to return to the Main Menu. To abandon Escape archiving the cache file, press. The name of the current cache file to which data is written is always 24TDIP.CAC. A new, empty file is initialized when the old cache data have been archived and the stack/block number has been reset. GDP Section 9, Page 14 October 2014

15 TIME DOMAIN INDUCED POLARIZATION PROGRAM SCREEN: CHANNEL TABLE DISPLAY SCREENS Cycle through the Channel Table screens by using. SCREEN: SETUP The SETUP screen is the initial Channel Table configuration displayed after starting the program. It can also be viewed by pressing and cycling through the screens. <0903d_24TDIP_Setup> In the SETUP screen, the column entry fields are: Ch, Calibration Found, Cmp Typ, Saturated Reading, Offset (RX1-RX0), N, Length (Ft/M), RX1 and RX2. Non editing fields are: Ch, Calibration Found, Saturated Reading, and Length. Ch The channel and card cage slot number for the A-D Card. Calibrate If proper board calibration records are not found in the calibration caches, the TDIP program will display a large exclamation point (!) next to the channel number in the Channel Table. Data acquisition can be completed without the proper calibration record loaded into the cache, but the data displayed on the GDP screen will assume calibration values of 1.0 mag, and 0.0 phase, and thus will not accurately represent the actual earth response. Calibration caches are ASCII files. Cmp Typ Channel component type selection. Any selection other than OFF will turn the channel ON. While the cursor is on a channel, the key is used to turn a channel Off or On. This key is the only way an operator can turn off a channel. Refer to the CH_OFF/ON function key described later. An Off channel can also be turned On by selecting a component type. October 2014 Section 9, Page 15 GDP-32 24

16 Ex, Ey, Ez Ref GDP INSTRUCTION MANUAL Electric field designators Designates the transmitter current reference input channel for CR measurements. Note: This field also indicates empty slots and cards not directly supported by the AMT program, such as NanoTEM cards. Saturate When the inputs to the channel, after applying the gain and attenuate, saturate the A-D converter, this field will indicate. Data acquisition can be completed, but the data acquired by the GDP will not accurately represent the actual earth response. Saturation is detected while gaining, and in real time during data acquisition. Offset Station distance along line, between the receiver reference location, RX0, and the positive electrode of the channel's dipole, RX1. It is used to calculate RX1 whenever the operator changes RX0. It is automatically adjusted whenever the operator changes RX1, or N. Offset = RX1 RX0 Note: Offset is the distance between the receiver reference location and a channel's positive electrode, not the distance to the center of a channel's dipole. N Length RX1 RX2 N-spacing (includes fractionals) for a channel designated as Ex, Ey, or Ez. Informative field showing the true distance (XYZ) between the channel electrodes. The location, along line, of the positive electrode, in S-space units. This value is automatically set by changes to RX0:RX, Offset, and N. It can also be set manually to match field conditions. See SCREEEN: XYZ EDIT for additional information. The location, along line, of the negative electrode, in S-space units. This value is automatically set by changes to Offset, N, and RX0:RX. It can also be set manually to match field conditions. See SCREEEN: XYZ EDIT for additional information. Note: Resistivity is calculated based on transmitter and receiver electrode locations, TX, RX1 and RX2 locations, not RX0, offset or N-values. The operator should always inspect the RX1 and RX2 values, after automatic update, to make sure they reflect the actual electrode locations in the field. Note: See the section covering SOFT FUNCTION KEYS for how configures the automatic update of RX1 and RX2 locations, based on TX and RX0 changes. Note: The X and Y locations for receiver and transmitter electrodes, or stations, may also be used as indexes into post processing station files. These files will then provide actual locations for post processing calculations. More information about this feature is available in the various post processing software manuals. GDP Section 9, Page 16 October 2014

17 SCREEN: GAIN/CRES TIME DOMAIN INDUCED POLARIZATION PROGRAM The GAIN/CRES screen can be viewed by pressing and cycling through the screens. <0903e_24TDIP_GainCRES> In the GAIN/CRES screen, the column entry fields are: Ch, Calibration Found, Cmp Typ, Saturated Reading, Offset (RX1-RX0), Gain, SPmv, and CRES. Non editing fields are: Ch, Calibration Found, Saturated Reading, and CRES. Gain Gain settings for stages 0 and 1 (in powers of 2). The attenuator settings are separated by a dash from the gain settings. More information about the gain stages can be found in chapter 16 of this manual. SPmv Self Potential or offset in millivolts. Initially set to CRES Contact Resistance, measured in Ohms and is obtained by pressing. October 2014 Section 9, Page 17 GDP-32 24

18 GDP INSTRUCTION MANUAL SCREEN: RESULTS The RESULTS screen can be viewed by pressing and cycling through the screens. <0903f_24TDIP_Results> In the RESULTS screen, the column entry fields are: Ch, Calibration Found, Typ, Saturated Reading, Vp, M, Rho, SEM, Win1, Win2, Win3, Win4 and Win5. Only the Comp Type is editable. The Win3, Win4 and Win5 are not normally visible on the smaller LCD screen unless Pg Up the view is shifted using. Vp M Rho SEM PREV FIELD Primary (ON) voltage, with magnitude calibration removed (which is the magnitude of the fundamental board calibrate, stored in the 24BOARD.CAL file). See the section towards the end of this manual on SCALING for more information. Average chargeability in millivolt-seconds per volt or milliseconds. Chargeability is determined by integrating from 0.45 to 1.1 seconds for both positive and negative polarities using an 8 second period. Data for other periods or frequencies are normalized to this standard. Apparent resistivity in ohm-meters. Standard error of the mean chargeability, in milliseconds, calculated for each cycle for frequencies of 1Hz and lower, or the average of 2 sec, for frequencies of 2Hz and above. Win1 to Win5 Time Domain normalized decay point value windows 1 through 5. The smaller LDC screen must be shifted in order to view the last 3 columns. GDP Section 9, Page 18 October 2014

19 TIME DOMAIN INDUCED POLARIZATION PROGRAM SCREEN: STACKS The STACKS screen can be reached by cycling. This screen displays the selected results for the last 5 Stacks of data, as each stack is acquired. When this screen is displayed, the cursor is moved to the results selector field. The selections are: Vp, M, Rho, SEM, SEMR, and Win1 through Win13. The SEM values are identical to those displayed in the RESULTS Screen. The SEMR value is accumulated over all the repeating stacks of an acquisition, where SEM represents the standard error for each individual screen. Note that while data are being collected, this selection cannot be changed. When data acquisition has finished, cycling this field will update the Channel Table display with the selected results for the last 5 stacks. The STACKS Channel Table is cleared at the start of an acquisition. <0903g_24TDIP_Stacks> October 2014 Section 9, Page 19 GDP-32 24

20 GDP INSTRUCTION MANUAL SCREEN: XYZ EDIT The XYZ EDIT screen can be reached by pressing, EDIT_EYZ, while the cursor is in the Channel Table. This screen allows full X, Y and Z location editing of the Transmitter, Receiver reference and all channel electrode locations. By recording X,Y,Z values for each electrode, the GDP can accommodate unorthodox resistivity/ip survey configurations which do not conform to a standard survey like in-line dipole-dipole or pole-dipole. X is distance parallel to line, Y is distance perpendicular to the survey line, and Z is depth below the surface. For a generic in-line dipole-dipole survey, all of the electrodes are on the survey line, so X = distance along line, Y is a constant value (line number by default) and Z is 0 for surface electrodes. X,Y,Z values represent distance in station number units, which are not required to be scaled to feet or meters. The GDP compares the unit dipole length in station numbers, S-space, with the unit dipole length in length units, A-space, to get the relationship of X,Y,Z coordinates to length units. If station numbers are in meters, then both S-space and A-space specify the unit dipole length in meters and have the same value. If station numbers are not scaled to meters or feet, then S-space and A-space will have different values and the GDP will use the ratio A-space/Sspace to get a length_unit/station_number scaling factor. The use of line and station numbers scaled to length units simplifies record keeping, especially for 3D surveys that use off-line electrodes. <0903h_24TDIP_XYZ_Edit> The Channel Table columns displayed are, Ch, Cmp Typ, Length, RX1, RY1, RZ1, RX2, RY2, and RZ2. There is one row in the channel table for each input channel. Ch Input channel index Cmp Type Measurement type, Ex, Ey, Ez, or Ref Length Receiver E component dipole length in station numbers. RX1 Receiver electrode 1 X location (distance parallel to line in station number units). GDP Section 9, Page 20 October 2014

21 TIME DOMAIN INDUCED POLARIZATION PROGRAM RY1 Receiver electrode 1 Y location (distance perpendicular to line in station number units). RZ1 Receiver electrode 1 Z location (depth below surface in station number units). RX2 Receiver electrode 2 X location (distance parallel to line in station numbers). RY2 Receiver electrode 2 Y location (distance perpendicular to line in station number units). RZ2 Receiver electrode 2 Z location (depth below surface in station number units). Just below the Channel Table are fields for specifying the transmitter (TX) electrode locations. AX Transmitter electrode 1 (distance parallel to line in station numbers). AY Transmitter electrode 1 (distance perpendicular to line in station number units). AZ Transmitter electrode 1 (distance depth below surface station number units). BX Transmitter electrode 2 (distance parallel to line in station numbers). BY Transmitter electrode 2 (distance perpendicular to line in station number units). BZ Transmitter electrode 2 (distance depth below surface station number units). Receiver reference location (RX0) is used to expedite the calculation of default electrode locations for standard survey arrays. The XYZ EDIT screen includes the fields for RX0 X,Y,Z at the bottom of the screen. In the screen shot example above, the Line value is 1, based on the TX: AY, BY and RX0: RY, locations. This indicates that this particular line's Y grid coordinate is 1 S-space unit. The Z locations all represent depth below the surface, in S-space units. Below are diagrams showing the relationship between Line and Station numbers, and X and Y coordinates of electrode locations. These also show the way S-Space and A-Space factor into that relation. On the left, we see a plan view of several survey lines and their stations. The S- Space has a value of 1, indicating that the station space numbering increments by the value of 1 for every A-Space distance. In this case the Station numbers match the X values of transmitter (TX;AX, BX), and receiver (RX0:RX, RX1, RX2) electrode locations. The Line numbers match the Y values of transmitter (TX:AY, BY), and receiver (RX0:RY, RY1, RY2) electrode locations. Z values, indicating depth below surface, would also be in the same units. The A- Space can be of any value. The plan view on the right depicts a similar layout, but in this case the S-Space is equal to the A-Space. The X, Y and Z values are all in the same units as the A- Space, either feet or meters. <0903i_ TDIP_waveform> October 2014 Section 9, Page 21 GDP-32 24

22 GDP INSTRUCTION MANUAL JOB_INFO SUBMENU The Job Information submenu can be accessed by pressing from the main menu. Entries in this menu are saved as metadata in the data cache and in the 24COMMON.INI file so that users do not have to re-enter these fields every time any of the acquisition programs are started. Entries in these fields carry into Zonge data processing programs as well. <0903j_24CR_JobInfo> GDP OPERATOR User defined identification. Alphanumerics permitted. JOB NAME User defined identification. Alphanumerics permitted. JOB FOR User defined identification. Alphanumerics permitted. JOB BY User defined identification. Alphanumerics permitted. JOB NUMBER User defined identification. Alphanumerics permitted. TX SN User defined identification. Alphanumerics permitted. The GRIDS area of the Job Info screen can be used to aid in post processing of the data. The information in these fields is stored in the cache, but is not used by the GDP or directly by any of the current post-processing software. OffSet This field can provide post processors with information about abbreviated location information, if used by the operator. The field provides a reference Label, as well as Survey X and Y offsets. In the event that electrode survey locations require many digits, these values could be used to minimize data entry. For example, if a survey was conducted in an area whose electrode locations had X values above , and Y values above , a location such as TX:AX of , and AY of , could be entered as TX:AX 862, and AY Ref1, Ref2, Calc These can be used as reference and a calculator to transform mapping Easting and Northing coordinates to Survey X and Y coordinates, or reverse. To use the calculator, the coordinates of two reference points must be known in both the Survey and Mapping coordinate systems. GDP Section 9, Page 22 October 2014

23 TIME DOMAIN INDUCED POLARIZATION PROGRAM For example, locations tx1, and tx2, are known. The Survey location of tx1 is 0X, and 0Y. The mapping coordinate of tx1 is East and North. The Survey location of tx2 is 3388X and 1017Y. The mapping coordinate of tx2 is East and North. After entering these values in the Ref1 and Ref2 fields, points can be calculated in either of the two coordinate systems by entering the coordinates of the known location in the Calc field. Entering a SurveyX value of 750, and a SurveyY value of 893 will result in calculated values of East and North. Entering values in the East and North columns will result in calculated SurveyX and SurveyY values. RESET FUNCTIONS is a multifunction key whose functions configure the automatic location update features of the TDIP program. These are designed to reduce the number of data entries that need to be made as a survey progresses. The reset functions are: RST_TX, RST_OFSET, and RST_N-SPC. RST_TX should always be used at the start of a survey. Either RST_OFSET or RST_N-SPC, should be use during initial channel spread configuration, and in some cases, when the Receiver reference location, RX0:, is moved above or below the Transmitter location TX. There are two methods by which the TDIP program automatically updates channel locations whenever the transmitter or receiver electrodes are moved. The Offset method is based on the location of electrodes with respect to the receiver itself. The N-space method is similar to the methods used by the GDP-32 II. Modifying the Transmitter electrode location and/or the Receiver reference location during the progress of a survey will cause the automatic update of channel electrode locations RX1 and RX2. With both methods, channels whose electrodes are in conflict with Transmitter electrodes should be turned off manually. The operator should decide which method to use before configuring the channels, then use the RST_OFSET or RST_N-SPC function to perform channel configuration. See the section A NOTE ON AUTOMATIC LOCATION UPDATES for more information and some examples. Note: Not using the Reset Functions, and not understanding the automatic location update features, can make the Survey Setup procedure seem difficult. Use of these features can simplify data entry and reduce errors. Note: also functions to turn channels Off or On while the cursor is in the Cmp Typ column of the Channel Table. RST_TX This function resets transmitter BX, BY and BZ locations, based on the ARRAY type, S-SPACE and the transmitter AX, AY and AZ, locations. It also initializes some features of the TDIP program based on various Line Setup fields of the Main Menu. The operator should press this key while initially setting up for a survey, after setting the fields ARRAY, A_SPACE, S_SPACE, TX:AX, TX:AY, RX0:RX or RX0:RY. This function is available while in the SETUP screen, and the cursor is not in the Channel Table. October 2014 Section 9, Page 23 GDP-32 24

24 GDP INSTRUCTION MANUAL RST_OFSET This function will re-sequence the Offset for channels above and below RST_N-SPC the channel row that the cursor is on. Pressing repeatedly will toggle between channel Offsets increasing or decreasing, effectively shifting a spread pattern above or below a transmitter location. The Offsets will increment or decrement by the S-SPACE value. The RX1 and RX2 values for all channels will be reset based on their Offset and the RX0 location. The N values for all channels will be reset based on their distance from the transmitter electrodes. This also places the program into the Offset mode for automatically updating electrode locations when RX0 or TX locations are modified. This function is available while the cursor is in the Offset column of the Channel Table. This function will re-sequence the N values for channels above and below the channel row that the cursor is on. Pressing repeatedly will toggle between channel N values increasing or decreasing, effectively shifting a spread pattern above or below a transmitter location. The N-values will increment or decrement by 1. The RX1 and RX2 values for all the channels will be reset based on their N-value and the TX location. The Offset values for all the channels will be reset based on their RX1 and RX0 locations. This also places the program into the N-space mode for automatically updating electrode locations when RX0 or TX locations are modified. This function is available while the cursor is in the N column of the Channel Table. This method of setup is similar to the methods used for the GDP-32 II. GDP Section 9, Page 24 October 2014

25 SCOPE FUNCTION TIME DOMAIN INDUCED POLARIZATION PROGRAM The Scope function allows the operator to see a real time graphical representation of the input signals to individual channels. When the cursor is in the Channel Table and in the row of an On channel, pressing the key will bring up a Scope display of the input signal to that channel. Moving the cursor to the row of another On channel will cause the Scope to display that input signal. Moving out of the Channel Table or to the row of an Off channel, will not affect the Scope. Pressing again, pressing Escape, or starting data acquisition will clear the Scope display. <0903k_24TDIP_Scope> The Scope display can be used to evaluate the input signal to a channel, as well as to evaluate the gain, attenuate and SP settings. The Scope's response time is faster than the analog panel displays, and will provide a better evaluation of the magnitude of higher frequency signals. While on the SETUP Screen, the operator can manually adjust the gain, attenuate and SP values, and evaluate their effect on the signal. If the trace of the signal reaches the top or bottom frame of the Scope it will be saturating the A-D converter, affecting measurements and interpretation of actual earth response. Note: On older versions of the Field Survey Program, the Automatic Gain algorithm does not apply an Attenuator setting. It assumes that the operator has set the transmitter to a level that will not require attenuation, relying instead on the increased dynamic range of the 24-bit analog converter. If the incoming signal does however require Attenuation, the MAN or SPONLY modes should be selected for GAIN. The SCOPE function can be used to inspect the incoming signal while making adjustments to the Transmitter Output. October 2014 Section 9, Page 25 GDP-32 24

26 GDP INSTRUCTION MANUAL 9.4 BOARD CALIBRATION SUBMENU The calibration data for the TDIP program is shared with several other GDP programs: CSAMT, CR, TEM SYSCHK and SYNC_CHK. The standard board calibrate buffer is saved as 24BOARD.CAL on the C:\ drive of the GDP. Board calibration data can be obtained and viewed in the Calibration submenu of the TDIP program. TDIP calibration data contains the 1 st, 3 rd, 5 th, 7 th and 9 th harmonics magnitude and phase values. The Calibration submenu is brought up by pressing from the main menu. Only the channels that are On in the Channel Table are included for calibration and viewing in this submenu. Below is a sample of the calibration submenu display. The Board Calibration values stored in 24BOARD.CAL are obtained by measuring each board's response to a 1.0v, 100% duty, square wave. The FFT results of these measurements are then divided by the FFT results of an ideal square wave. This results in a Board Calibrate factor. The magnitude of the Board Calibrate for the fundamental frequency of investigation is used to decalibrate the time domain readings used in the TDIP program. <0904a_24TDIP_CalCal> The Channel Table for the calibration submenu contains the following fields: BOARD Gain Analog board serial number(s), in channel order. This display only includes channels that were On when the submenu was activated. Calibration values are associated with board serial numbers as opposed to channels, since the operator may exchange cards between channels within the GDP case. These settings can be made by the operator in order to obtain calibration sets at different gain and attenuation values. The gaining and attenuation circuitry on the analog boards can have a minor effect on the overall measurement of the incoming signal. If a high degree of accuracy is required, calibrations can be performed at specific gain settings. Calibration sets for different gain settings are all maintained within the same calibration file. Whenever readings are GDP Section 9, Page 26 October 2014

27 TIME DOMAIN INDUCED POLARIZATION PROGRAM decalibrated, and a calibration for a specific gain setting is not available, the program uses the calibration values for the 00-0 gain. The AUTOCAL METHOD described below will not automatically cycle through all the possible gain setting variations. The operator must perform an AUTOCAL calibration for each variation of gain setting. Thus, a calibration value for a gain of 11-0, cannot be obtained by perform calibrations for a 10-0 setting and a second calibration for a 01-0 setting. Board Cal This displays the magnitude and phase values for the board calibration value just written to, or recalled from, the calibration file. The column label for the values displayed during either a AUTO_CK or 1SHOT_CK is changed to Cal File for clarity and comparison to the values obtained and displayed in the Check columns described below. System Cal This displays the magnitude and phase of the raw values just obtained during a calibration. If no calibration was just performed, these display default values. These values are not recorded or maintained in memory. The system calibrate values represent the response of the system to the calibration signal input to the cards. Because the calibration signal is an ideal square wave, the FFT values of an ideal square wave are factored out of the readings in order to obtain a general board response, the Board Cal. The Board Cal values are those which are actually recorded in the cal file and used to decalibrate readings during data acquisition. Check These are board response values obtained during either the AUTO_CK or 1SHOT_CK procedures as described below. These provide the operator a visual confirmation of calibration and board quality made during the check procedures. These values are not maintained in a file or in memory, and will display default values if a check reading has not just been performed. How closely these values match to those in the Cal File columns is an indication of data quality. The calibration and viewing parameters are set in the following fields: FREQ CYCL The calibration frequency setting which ranges from to 8192 Hz. The calibration values for the fundamental frequency, from the calibrate file, will be displayed as frequencies are selected. The setting for the number of cycles to take when taking the calibration readings. NOTCH The Notch filter setting for the calibration set. This setting must be made manually and is not automatically changed during the AUTOCAL METHOD of calibration. METHOD The operation method for the calibration. The selected calibration METHOD will AUTOCAL be performed when the operator presses the key. Perform calibration starting at the selected FREQ, and automatically sequencing up to the highest frequency of 8192 Hz. This will automatically select sample rates, and high pass filter settings for each frequency of the calibration set. Calibration sets include the magnitude and phase for the 1 st, 3 rd, 5 th, 7 th, and 9 th harmonics, which are written to Enter October 2014 Section 9, Page 27 GDP-32 24

28 GDP INSTRUCTION MANUAL AUTO_CK the calibration file. This automatic calibration does not cycle through the possible NOTCH or gain values. Calibration sets for specific NOTCH and gain settings can be included in the calibration file, but calibrations must be made for each selection combination. This selection will perform calibration in exactly the same manner as the AUTOCAL method described above, however rather than writing the results to the calibration file, it compares the resulting values to those already in the file. The automatic sequencing through the various frequencies progresses automatically up through the highest frequency, displaying the difference for each setting. If the difference between the resulting value and the value in the cache exceeds the delta phase percent limit set in the dθ% LIM field described below, the program will issue an audible alarm and pause for an operator response. The operator may press Escape to cancel the check, or any other key to continue. <0904b_24TDIP_CalCheck> Note: One method of verifying both the calibration file and the operation of the TDIP program is to perform calibration with the TDIP program. Then exit TDIP and start one of the other programs that share the 24BOARD.CAL file, CR, or CSAMT. From the Calibrate submenu in that program, perform the AUTO_CK procedure. 1SHOTCAL Perform calibration for one FREQ setting. It will cycle through the harmonics, sample rates, and high pass filter settings for that frequency. The results are written to the calibration file. 1SHOT_CK Perform a calibration in exactly the same manner as the 1SHOTCAL method and compare the resulting values to those already in the cache. If the difference exceeds the delta phase percent limit set by dθ% LIM, the program will issue an audible alarm. GDP Section 9, Page 28 October 2014

29 TIME DOMAIN INDUCED POLARIZATION PROGRAM SYS_CK This system check selection will cause a calibration signal to be enabled during data acquisition. The MODE selection will control how the signal is routed. The CAL V setting will set the reference voltage. Pressing the Enter key while this method is set will have no effect. To enable this method the operator must press the Escape key to return to the Main Menu, and then perform the system check readings by pressing. If the MODE is set to INTERNAL, the signal will only be routed to those channels that were On when the Calibration submenu was activated. For the EXTERNAL MODE, the operator must route the signals externally. No automatic checks are performed when the readings are made. The Main Menu will display a message below the date and time, indicating that the system check is enabled, as in the sample screen display below. Enter <0904c_24TDIP_SysCheck.png> MODE The selections are INTERNAL and EXTERNAL. INTERNAL will connect the calibration reference signal through internal circuits of the GDP, directly to the channel inputs for calibration. EXTERNAL will connect the calibration signal to the CAL+ and the CAL- terminal on the outside of the GDP case. The operator must then route the signal from these outputs through the desired channel components, and to the channel input terminals for calibration. Note: The calibration file does not maintain separate data sets for INTERNAL and EXTERNAL calibrations. The operator must decide which type of calibration is required and perform a full calibration for the desired MODE. October 2014 Section 9, Page 29 GDP-32 24

30 CAL V GDP INSTRUCTION MANUAL Set the calibration signal voltage, and can only be made by the operator when the METHOD selection is SYS_CK and performing a system check. During the calibration and cal check METHODS, the value of the cal voltage is automatically adjusted when gain or attenuate settings are adjusted. The voltage is adjusted so that the signal to the A-D converter is 1.0 volts, after being modified by the gain and attenuate circuits. All calibration values are based on a 1.0 volt signal being read by the A-D converters. dθ% LIM Set a stop limit while performing an AUTO_CK or 1SHOT_CK check of the calibration data in the calibration file and calibration readings made during the check. The delta phase percentage is calculated as the difference between the calibration phase just measured and the phase recorded in the file, divided by the phase recorded in the file, represented as a percent. Note: The limit is normally set to 1% for running the AUTO_CK procedure, and can detect basic system or card errors. Generally the measured phase difference is well below this. Higher frequencies, which have calibrates with a greater number of cycles, can be expected to have phase differences of less than 0.05%. Lower frequencies, particularly the lowest frequency of a sample rate 0.016Hz, 0.063Hz, and 2Hz, can have higher differences around 0.2 %. When the NOTCH filter is set in, the differences near the harmonics of the NOTCH, can have significantly higher values, and may exceed the 1% limit. This does not indicate a hardware problem. GDP Section 9, Page 30 October 2014

31 9.5 GATHERING DATA PROGRAM START UP TIME DOMAIN INDUCED POLARIZATION PROGRAM During start up, the TDIP program will perform various system checks. It will search and identify all cards installed in the GDP. It will open and index the calibration file. The input parameters from the last TDIP session will be loaded into the display. When complete, the STATUS line will indicate Ready, and the message Press CONTINUE to take data will be displayed. If the GDP detects that the version of the board calibration file is incompatible with the version of the TDIP program, the old calibrate file will be renamed to BOARDTD.CAL and a new, empty 24BOARD.CAL will be created. An audible warning will be made and the GDP will display a message to the operator that a new calibration must be performed. The GDP will wait for a key press in response before the startup process continues. If no calibrate files are found, the GDP will make an audible warning, inform the operator of the problem, and wait for a key press in response before the startup process continues. The required board calibration file is 24BOARD.CAL. A new empty file will be initialized. The GDP will not inform the operator if the files do exist, but are empty. The No Cal Found symbol, '!', in the Channel Table will be the only indicator of missing calibrates. The GDP must perform the board calibrates. DATA ACQUISITION When the STATUS is Ready, the operator can proceed to set the various parameters required for the data acquisition. After filling in the parameters for Job Information, Line Setup, Acquisition Configuration and setting up the Channel Table, the operator should confirm that calibrates are found and input signals are good. Use of the SCOPE can detect channel saturation, poor connections, and excessive powerline noise. Pressing sequence. Enter will start the data acquisition Enter Immediately after pressing, the GDP will set gains. When the selected gain method has completed, the GDP acquisition will synchronize with the timing card and indicate that it is taking data. At frequencies of 2 Hz and above, no other indication of collecting data will be observed, as the GDP is using its full resources to read the A-D cards and store the raw data into the computer memory. For 1 Hz and below, a progress bar will be displayed showing the time left for taking data. When data has been acquired, the results will be calculated and displayed. When acquiring a single stack of data, the GDP will display the message Press ESCAPE to discard, CONTINUE to save Hit Key, make an audible signal, and then pause for the operator's response. The operator must then respond. The data will be written to the flash card or discarded, based on their review of the results. After responding, the GDP will write the data, make an audible signal, and be Ready for further acquisitions. October 2014 Section 9, Page 31 GDP-32 24

32 STOP ACQUISITION GDP INSTRUCTION MANUAL If the operator wishes to cancel the acquisition of data at any time before normal completion of a Escape stack, or to terminate acquisition of a large number of stacks, pressing the key will stop the process. Depending on sample rate and the various stages of data acquisition, the GDP may stop immediately, or it may take a few moments to finish before it is ready. ACQUISITION ERRORS If there are any processing errors due to hardware or other acquisition issues, the GDP will make an audible signal, display a message to the operator, and wait for a response before going to the Ready state. A history of error and warning messages is displayed below the Main Menu, in an area not normally visible on the smaller LCD screen. These messages can be useful to monitor progress and to review any messages associated with an error. 9.6 VIEWING DATA After stacks of data have been acquired and saved to the cache file, the data can be reviewed by pressing to start the Cache Viewer. The initial display will display zero values in the table. The operator can make selections for SET (or BLOCK), PLOT type, CH (channel), and CYCLE. The SET value identifies a group of stacks, with the same frequency, and channel configuration (spread). Sets are numbered sequentially as they are identified when the cache is initially scanned. The FREQ field displays the frequency of a Set or Block. Enter Press to scan the cache and present the data. The display is not immediately updated upon making any of the selections in order not to scan the cache with each key press, thus slowing down response. The PLOT types for TDIP are: Window, Rho_N, M_N, Stack, and TimeSr. The Window plots present the data for Sets. The Rho_N, and M_N, plots present a pseudosection of all the blocks in the cache. The Stack and TimeSr, plot data for individual blocks. The operator can toggle between a GRAPH or TABLE view of the data by pressing. When in the TABLE view, pressing more channels to view. will shift the columns to other channels if there are GDP Section 9, Page 32 October 2014

33 TIME DOMAIN INDUCED POLARIZATION PROGRAM The Window Plot presents the averaged results for a Set of blocks. The Time is in microseconds. The window value is the normalized decay point in 10's of milliunits. <0906a_24TDIP_CacVu_Win_Tabl> <0906b_24TDIP_CacVu_Win_Graph> October 2014 Section 9, Page 33 GDP-32 24

34 GDP INSTRUCTION MANUAL The Rho_N Plot presents the resistivity vs N-values for all the blocks on the cache, represented as a Pseudosection. <0906c_24TDIP_CacVu_RhoN_Tabl> <0906d_24TDIP_CacVu_RhoN_Graph> GDP Section 9, Page 34 October 2014

35 TIME DOMAIN INDUCED POLARIZATION PROGRAM The M_N Plot presents the Chargeability vs N-values for all the blocks on the cache, represented as a Pseudosection. <0906e_24TDIP_CacVu_MN_Tabl> <0906f_24TDIP_CacVu_MN_Graph> October 2014 Section 9, Page 35 GDP-32 24

36 GDP INSTRUCTION MANUAL The Stack Plot presents the Mag vs time values, averaged over the entire acquisition period, for a single block. When in the TABLE view, the and keys scroll up or down the table, increasing or decreasing the cycle time. When viewing the GRAPH these keys have no function. <0906g_24TDIP_CacVu_Stack_Tabl> <0906h_24TDIP_CacVu_MN_Graph> GDP Section 9, Page 36 October 2014

37 TIME DOMAIN INDUCED POLARIZATION PROGRAM The TimeSr Plot presents the voltage vs time values for a single cycle of the acquisition period, for a single block. When viewing the time series, each CYCLE can be selected by pressing SELECT DN End. In TABLE view, the and keys scroll up or down the table, increasing or decreasing the cycle time. In GRAPH view, the and keys increase or decrease the cycle being displayed. The key will have no function. <0906i_24TDIP_CacVu_Time_Tabl.png> <0906j_24TDIP_CacVu_Time_Graph.png> October 2014 Section 9, Page 37 GDP-32 24

38 9.7 CACHE FILE GDP INSTRUCTION MANUAL The TDIP data cache is much like that of other GDP programs. It contains binary data blocks with ASCII metadata descriptors. See chapter 7, DATA, FILE AND PROGRAM TRANSFER for more detailed information. Note: Though the cache file can be viewed and partially read with simple text editing programs, doing so can irrevocably destroy the navigation pointers within the file, or the data itself, resulting in total loss of data. The TDIP cache contains the following records for every stack recorded: Header Cal WinDefs ASCII record contains survey data including: job descriptors, locations, channel component types, GPS timing, and other data required for post processing. This portion of the cache can be edited with the CACEDIT program. ASCII record containing calibration factors for all channels. Begin and end point count and times for the chargeability and decay windows. Time Series An optional binary data record containing all the raw A-D data readings for all channels. Stack Data A binary data record containing an average of the time series, stacked into a single cycle. Windows Summary Quality A binary data record of the Vp, chargeability and the decay windows, for each channel. A binary data record containing IPSEM, Vp, IPM, and ARes, for each channel. ASCII record of the internal temperature, humidity and battery voltage at the end of acquisition. The following is an example of the Header metadata for a CR cache. HEADER.TYPE,Survey DATA.VERSION,1.00 DATA.BLOCK,1 DATA.SKIP,0 DATA.STACKCTDN,2 GDP.DATE,07/22/2014 GDP.TIME,10:13: SURVEY.TYPE,TDIP SURVEY.ACQMETHOD,stack SURVEY.ARRAY,D-D LINE.NAME,0 LINE.NUMBER, LINE.DIRECTION,N LINE.SPREAD,88 JOB.NAME,Quality Assurance JOB.FOR,Customer JOB.BY,Engineering JOB.NUMBER, JOB GDP.OPERATOR,Zonge Field Crew GDP.TYPE,GDP32-24 GDP.PROGVER,TDIP_1.37j GDP.SIGSOURCE,ESys GDP.CALVOLTS, GDP.SYNC,Manual GDP.GAINMETHOD,Once GDP.GAINMODE,Noisy GDP.FPSN,328 GDP Section 9, Page 38 October 2014

39 TIME DOMAIN INDUCED POLARIZATION PROGRAM GDP.SN,3252 GDP.TCARDSN,336 GDP.NUMCARD,8 GDP.ADCARDSN,C83C,C87E,C8DA,C880,C83D,C8FF,C875,E8D2 GDP.ADCARDSND,60,126,218,128,61,255,117,210 GDP.CARDTYPE,ANA24CARD,ANA24CARD,ANA24CARD,ANA24CARD,ANA24CARD,ANA24CARD,ANA24CARD,ANA24CARD GDP.ADCARDVER,09,8B,0B,89,09,0B,0B,09 GDP.ADCARDFEAT,05,07,07,07,05,07,07,07 GDP.BAT, GDP.TEMP, GDP.HUMID, GRID.XYOFFSET,490000: ,"TEST" GRID.REF1,0:0,490862: ,"tx1" GRID.REF2,3388:1017,494250: ,"tx2" GRID.CALC,750:893,491612: ,"" TX.STN,100 TX.XYZ1,4:1:0 TX.XYZ2,5:1:0 TX.SN,123 TX.FREQ,8 TX.DUTY,0.5 TX.AMP, TX.SENSE,1 TS.ADFREQ,32768 TS.NCYCLE,16 TS.NWAVEFORM,4096 TS.DECFAC,1 TS.NPNT,65536 RX.STN,8 RX.AZIMUTH,88 RX.ASPACE,100 RX.SSPACE,1 RX.XYZ0,8:1:0 RX.XYZ1,10:1:0,9:1:0,8:1:0,7:1:0,6:1:0 RX.XYZ2,11:1:0,10:1:0,9:1:0,8:1:0,7:1:0 RX.LENGTH,100,100,100,100,100 RX.ADDELAY,81 LAB.ID, LAB.AREA,100 LAB.LENGTH,1 UNIT.LENGTH,m CH.NUMON,5 CH.ADCARDSN,C83C,C87E,C8DA,C880,C83D CH.GDPSLOT,1,2,3,4,5 CH.FACTOR, e-007, e-007, e-007, e-007, e-007 CH.GAINFACTOR,1,1,1,1,1 CH.GAIN,00-0,00-0,00-0,00-0,00-0 CH.NUMBER,2,1,0,-1,-2 CH.NOTCH,NONE,NONE,NONE,NONE,NONE CH.HIGHPASS,NONE,NONE,NONE,NONE,NONE CH.LOWPASS,14000,14000,14000,14000,14000 CH.CRES,0,0,0,0,0 CH.CMP,ex,ex,ex,ex,ex CH.STATUS,0000,0000,0000,0000,0000 CH.SP,-3,0,0,0,-1 <0906i_24TDIP_CacHeader.txt> October 2014 Section 9, Page 39 GDP-32 24

40 GDP INSTRUCTION MANUAL 9.8 A NOTE ON AUTOMATIC LOCATION UPDATES The automatic location update features of the TDIP program are designed to reduce the number of data entries required as a survey progresses. The reset functions configure these update features and are accessed through. The context of the cursor on screen controls the functionality of. The functions are labeled: RST_TX, RST_OFSET, and RST_N-SPC. RST_TX should always be used at the start of a survey. Either RST_OFSET or RST_N-SPC, should be use during initial channel spread configuration, and whenever the Receiver reference location, RX0:, is moved above or below the Transmitter location TX: There are two methods by which the TDIP program automatically updates channel locations whenever the transmitter or receiver electrodes are moved. The Offset method is based on the location of electrodes with respect to the receiver itself. The N-space method is similar to the methods used by the GDP-32 II. Modifying the Transmitter electrode location and/or the Receiver reference location during the progress of a survey will cause the automatic update of channel electrode locations RX1 and RX2. The operator should decide which method to use before configuring the channels, then use the RST_OFSET or RST_N-SPC function to perform channel configuration. Note: Not using the Reset Functions, and not understanding the automatic location update features, can make the Survey Setup procedure seem difficult. Use of these features can simplify data entry and reduce errors. Note: also functions to turn channels Off or On while the cursor is in the Cmp Typ column of the Channel Table. RST_TX Reset transmitter BX, BY and BZ locations, based on the ARRAY type, S- SPACE and the transmitter AX, AY and AZ, locations. This function also initializes some features of the TDIP program based on various Line Setup fields of the Main Menu. RST_OFSET The operator should press this key after setting the fields ARRAY, A-SPACE, S-SPACE, TX:AX, TX:AY, RX0:RX or RX0:RY. This function is available while in the SETUP screen, and the cursor is not in the Channel Table. Re-sequence the Offset for channels above and below the channel row that the cursor is on. Pressing repeatedly will toggle between channel Offsets increasing or decreasing, effectively shifting a spread pattern above or below a transmitter location. The Offsets will increment or decrement by the S-SPACE value. The RX1 and RX2 values for all the channels will be reset based on their Offset and the RX0 location. The N-values for all channels will be reset based on their distance from the transmitter electrodes. This also places the program into the Offset mode for automatically updating electrode locations when RX0 or TX locations are modified. This function is available while the cursor is in the Offset column of the Channel Table. GDP Section 9, Page 40 October 2014

41 TIME DOMAIN INDUCED POLARIZATION PROGRAM Note: N-values are equivalent to the distance between the closest electrodes of the channel and transmitter, and related to the depth of investigation. The Offset method that the TDIP program uses to update locations as the survey progresses, is based on the RX0 reference being the actual location of the receiver, not the location of an electrode nearest the transmitter. The channel offset values represent the physical distance between the RX1 electrode and the actual receiver. For standard surveys the pattern, or spread, of electrodes does not change as the survey progresses. Channels may be turned On or Off, but unless the receiver itself moves, the electrodes do not, and when the receiver does move, the pattern in which the electrodes are laid remains essentially the same. The operator should first set the ARRAY type, A-space, S-space and TX locations, then press, RST_TX. After spreading out the electrodes, the operator should identify the station whose positive electrode is nearest the receiver. This station number should be entered as the RX0:RX location. The cursor should then be moved to the Offset column of the Channel Table, and to the row for that nearest channel. The offset should be set to 0, and while the cursor is still on that field, RST_OFSET, should be pressed. The Offset and RX1 locations for all ON channels will then be reset. If the layout of the channels is reversed, press order. again to reverse the Note: Pressing will only affect channels that are ON therefore any channels that are OFF will not have correct Offset values. Pressing at a later time, while the cursor is again on the channel with the nearest electrode, will fix the situation. It is best to have all channels ON. RST_N-SPC This function will re-sequence the N values for channels above and below the channel row that the cursor is on. Pressing repeatedly will toggle between channel N-values increasing or decreasing, effectively shifting a spread pattern above or below a transmitter location. The N-values will increment or decrement by 1. The RX1 and RX2 values for all the channels will be reset based on their N-value and the TX location. The Offset values for all the channels will be reset based on their RX1 and RX0 locations. This also places the program into the N-space mode for automatically updating electrode locations when RX0 or TX locations are modified. This function is available while the cursor is in the N-column of the Channel Table. This method of setup is similar to the practice used for the GDP-32 II. The N-space method that the TDIP program uses to update locations is based on the RX0: RX reference being the lowest numbered electrode for the dipole closest October 2014 Section 9, Page 41 GDP-32 24

42 GDP INSTRUCTION MANUAL to the transmitting dipole (or pole). The channel N-values are the depth of investigation for the channel which is equivalent to the distance between the closest electrodes of the channel and transmitter. For standard surveys, the pattern, or spread, of electrodes out from the receiver does not change as the survey progresses. Channels may be turned on or off, but unless the receiver itself moves, the electrodes do not, and when the receiver does move, the pattern in which the electrodes are spread out remains essentially the same. When the receiver moves to the opposite side of a transmitter, the lower numbered channels must be arranged to be closer to the transmitter. The transmitter electrode polarity must be changed. The operator should first set the ARRAY type, S-space and TX locations, then press RST_TX. The RX0:RX location should be set to the lowest numbered electrode for the dipole closest to the transmitting dipole (or pole). The cursor should then be moved to the N-column of the Channel Table, and to the row for that channel nearest the transmitter. The N-values should be set appropriately, and while the cursor is still on that field, RST_N-SPC, should be pressed. The N-values and RX1 locations for all ON channels will then be reset. If the layout of the channels is reversed, press again to reverse the order. Note: Pressing will only affect channels that are On, therefore any channels that are Off when it is pressed will not have correct N-values. Pressing at a later time, while the cursor is again on the channel nearest the transmitter, will fix the situation. It is best to have all channels ON. RST_OFSET EXAMPLE To setup the TDIP program for the example spread below, the following steps can be followed: Set ARRAY to D-D. Set A-SPACE and Ft/M as required. Set S-SPACE to 1. Set TX: AX to 4, Set AY as required. Press. Set RX0:RX to 0. Set Cmp Typ for Channels 1-6, to Ex. Set Offset for Channel 3, to 0. DO NOT MOVE THE CURSOR. Press. If the sequence of Offsets for the other channels are reversed, or the RX1 values are reversed, press again. In this example the lower numbered GDP Section 9, Page 42 October 2014

43 TIME DOMAIN INDUCED POLARIZATION PROGRAM channels are connected to higher numbered electrodes nearest the transmitter, but this is not required. <0909a_24TDIP_Setup_Spread_1_1> <0909b_24TDIP_Setup_1_1> After setting the other acquisition parameters, the GDP will be ready to acquire data. October 2014 Section 9, Page 43 GDP-32 24

44 GDP INSTRUCTION MANUAL When the transmitter electrodes are to be moved, use the following sequence of steps: Set TX: AX to 3. Note: The N-value for channel 1 has changed to 0, indicating that the channel is in conflict with a transmitter electrode, and should be turned Off. The channel is not automatically turned off, however an Error will be issued if an attempt is made to acquire data while the channel is on. Turn off channel 1. <0909c_24TDIP_Setup_Spread_1_2> <0909d_24TDIP_Setup_1_2> The GDP will be ready to acquire data. GDP Section 9, Page 44 October 2014

45 TIME DOMAIN INDUCED POLARIZATION PROGRAM When the receiver moves to stations above the transmitter, the operator could follow past procedures, and turn around the receiver so that the lower numbered channels are still towards the transmitter and reverse the transmitter polarity. For this example we will leave the channel spread the same, the lower numbered channels will still be connected to higher numbered electrodes. Channel and transmitter polarities do not need to change. Use the following steps: Turn on channel 1. Set RX0:RX to 8, because the receiver moved to that location. <0909e_24TDIP_Setup_Spread_1_3> <0909f_24TDIP_Setup_1_3> The GDP will be ready to acquire data. October 2014 Section 9, Page 45 GDP-32 24

46 GDP INSTRUCTION MANUAL When the transmitter electrodes are to be moved, use the following sequence of steps: Set TX: AX to 4. Note: The N-value for channel 6 has changed to 0, this indicates that the channel should be turned OFF. The channel is not automatically turned OFF however an Error will be issued if an attempt is made to acquire data while the channel is ON. Turn off channel 6. <0909g_24TDIP_Setup_Spread_1_4> <0909h_24TDIP_Setup_1_4> The GDP will be ready to acquire data. GDP Section 9, Page 46 October 2014

47 TIME DOMAIN INDUCED POLARIZATION PROGRAM Note: An advantage to this method is that two receivers with similar spreads and setups, can acquire data simultaneously on opposite sides of the transmitter without changing transmitter or channel polarities. The basic rules to remember are: RX0 is the actual location of the receiver. Offset is the distance between the receiver, RX0, and a channel's positive electrode, not the distance to the center of the channel's dipole. The channel whose positive electrode is at or nearest to the receiver, has the offset of 0, and RST_OFSET, is pressed while the cursor is on that channel, and in the Offset column. The positive electrode of a channel, is nearest the positive electrode of the transmitter. When on the opposite side of the transmitter, the negative electrode of a channel, is nearest the negative electrode of the transmitter. The RX1 and RX2 electrode locations must be verified, as these values are used in processing. These locations may be set directly, for special circumstances, after TX and RX0 locations have been set. RST_N-SPC EXAMPLE To setup the TDIP program for the example spread below, the following sequence of steps can be followed: Set ARRAY to D-D. Set A-SPACE and Ft/M as required. Set S-SPACE to 1. Set TX: AX to 4, Set AY as required. Press. Set RX0:RX to 1. Set Cmp Typ for Channels 1-6, to Ex. Set N for Channel 1, to 1. DO NOT MOVE THE CURSOR. Press. If the sequence of N's for the other channels are reversed, or the RX1 values are reversed, press again. October 2014 Section 9, Page 47 GDP-32 24

48 GDP INSTRUCTION MANUAL <0909i_24TDIP_Setup_Spread_2_1> <0909j_24TDIP_Setup_2_1> After setting the other acquisition parameters, the GDP will be ready to acquire data. GDP Section 9, Page 48 October 2014

49 TIME DOMAIN INDUCED POLARIZATION PROGRAM When the transmitter electrodes are to be moved, use the following sequence of steps: Set TX: AX to 3. Set RX0:RX to 2. Note: Changing RX0:RX at this point is not strictly required to obtain correct RX1 and RX2 locations, but will match the procedures of the GDP-32 II. Note: The N-value for channel 1 has changed to 0, indicating that the channel is in conflict with a transmitter electrode and should be turned OFF. The channel is not automatically turned OFF however an Error will be issued if an attempt is made to acquire data while the channel is ON. Turn off channel 1. <0909k_24TDIP_Setup_Spread_2_2> <0909l_24TDIP_Setup_2_2> The GDP will be ready to acquire data. October 2014 Section 9, Page 49 GDP-32 24

50 GDP INSTRUCTION MANUAL When the receiver moves to stations above the transmitter, the operator should follow past procedures, connecting the channels to the receiver so that the lower numbered channels are still towards the transmitter. The transmitter polarity should be reversed. Use the following steps: Turn on channel 1. Set RX0:RX to 5 Set N for Channel 1, to 1. DO NOT MOVE THE CURSOR. Press because the channel sequence has been changed. If the sequence of N's for the other channels are reversed, or the RX1 values are reversed, press again. Change the polarity of the transmitter electrodes. <0909m_24TDIP_Setup_Spread_2_3> GDP Section 9, Page 50 October 2014

51 TIME DOMAIN INDUCED POLARIZATION PROGRAM <0909n_24TDIP_Setup_2_3> The GDP will be ready to acquire data. October 2014 Section 9, Page 51 GDP-32 24

52 GDP INSTRUCTION MANUAL When the transmitter electrodes are to be moved, as in the next example, use the following steps: Set TX: AX to 4. Set RX0:RX to 6 Note: Changing RX0:RX, at this point, is not strictly required to obtain correct RX1 and RX2 locations, but will match the procedures of the GDP-32 II. Note: The N-value for channel 1 has changed to 0, this indicates that the channel should be turned off. The channel is not automatically turned off, however an Error will be issued if an attempt is made to acquire data while the channel is on. Turn off channel 1. <0909o_24TDIP_Setup_Spread_4_1> GDP Section 9, Page 52 October 2014

53 TIME DOMAIN INDUCED POLARIZATION PROGRAM <0909p_24TDIP_Setup_4_1> The GDP will be ready to acquire data. Note: As with the GDP-32 II, the procedures can be altered so that two receivers can acquire data simultaneously, on opposite sides of the transmitter, without changing transmitter or channel polarities The basic rules to remember are: RX0 is the lowest numbered electrode for the dipole closest to the transmitting dipole (or pole). N-values are the depth of investigation for the channel which is equivalent to the distance between the closest electrodes of the channel and transmitter. The N-value for channel closest to the transmitter should be set as appropriate, and, RST_N_SPC, is pressed while the cursor is on that channel, and in the N- column. The negative electrode of a channel, is nearest the negative electrode of the transmitter. This may require reversing the polarity of the transmitter electrodes. With special setups the positive electrode of a channel is nearest the positive electrode of the transmitter. The RX1 and RX2 electrode locations must be verified, as these values are used in processing. These locations may be set directly for special circumstances, after TX and RX0 locations have been set. October 2014 Section 9, Page 53 GDP-32 24

54 9.9 A NOTE ON SCALING GDP INSTRUCTION MANUAL The following convention is used for all measured and calculated parameters: Voltage (magnitudes) displayed in volts. Current displayed in amperes. Phase displayed in milliradians. Apparent resistivity displayed in ohm-meters. Dipole spacings displayed in meters. SP displayed in millivolts SEM displayed in milliradians If scaling is necessary on these values, the following labels are appended to the end of the number string: M - Mega units K - Kilo units m - milli units u - micro units GDP Section 9, Page 54 October 2014

55 9.10 ALGORITHMS TIME DOMAIN INDUCED POLARIZATION PROGRAM The equation used for calculating the time domain (see below) is the equation used in Swift (1973). By inverting the negative half-cycle, chargeabilities are averaged over each cycle for the specified number of cycles. The output will be in milliseconds or millivolt-seconds per volt. This equation was originally given to Zonge by Newmont as the "Newmont Standard" chargeability. Since that time it has been determined that this is not really the Newmont standard, but it can be obtained by multiplying this "Zonge Standard" by In order to reduce confusion, we have retained the original chargeability definition, and convert to the Newmont Standard (if desired) in our data processing programs. For the "Zonge" standard at Hz (8 second perod): M = T Vp Vs Where T is the cycle period of 8 seconds, 8192 is the number of points per cycle, and the integral of the secondary (Vs) or off-time voltage is from 0.45 sec to 1.1 sec. With 8192 points sampled per cycle, Vs is summed over 666 counts out of 2048 per quartercycle. The 13 windows defining the off-time decay waveform are obtained on 148 ms intervals at Hz. The closest combination of windows to get an approximation of the chargeability is a sum of windows 4, 5, 6, and 7. At Hz this effectively integrates from 500 to 1100 ms, which is 50 ms shorter than the standard window, so this approximation will always be slightly lower than the Zonge Standard chargeability. The table below shows the following values for the frequencies available in TDIP. Freq SR NPts VpPnts MStrt MPts WStrt WPts <0910a_24TDIP_WinPoints.txt> SR A-D sampling rate, samples per second. Npts Number points per cycle. VpPnts Number points averaged for Vp. Mstrt Starting point for summing Vs, for M. Mpts Number of points to be summed for M. Wstrt Starting point for first decay window, W). Wpts Number of points to be summed for each decay window. With W i = Normalized decay point value in 10's of milliunits = (Sum of Vs over the window interval Wpts)/(Vp x WPts) October 2014 Section 9, Page 55 GDP-32 24

56 GDP INSTRUCTION MANUAL The chargeability, M = T/NPts x 1.87 / Vp x ΣVs / 10 where: T/NPts is, the digitization interval 1.87 is the Swift constant Vp is the measured on-time voltage. ΣVs is the summation of off-time voltages, MPts, from point Mstrt. Reference: Swift, C.M., Jr, 1973, The L/M parameter of time domain IP measurements --- a computational analysis, Geophysics, v 38, p TIME DOMAIN WINDOW TIMING INFORMATION <0910b_TDIP_waveform> GDP Section 9, Page 56 October 2014

57 TIME DOMAIN INDUCED POLARIZATION PROGRAM 9.11 SAMPLE MENUS FOR "LABROX" ARRAY Selecting the ARRAY type, Lab, causes the fields in the Line Setup are of the Main Menu to change. The TX and RX0 locations are replaces with SAMPLE ID, SAMPLE LEN and SAMPLE AREA. <0911a_24TDIP_Results_LabRox> Channels 1 and 2 are customarily set as shown. Channel 1 (Ex) is the voltage across the rock sample, Channel 2 (Ref) is the voltage across the decade resistance box or sense resistor. Here the length, SAMPLE LEN, and cross-sectional area of the rock sample, SAMPLE AREA, are input to the system for calculation of the resistivity of the sample. The SENSE is set to the value of the current measuring resistor (typically a decade resistance box) that is set equal to the resistance of the rock sample. SAMPLE ID is an informative alphanumeric field. S-space is not used. Use the CRES function key to get an approximate value for the rock resistance for setting the shunt resistor. The RESULTS screen displays the resistivity of the sample, in place of the Rho column, and the channel Gain settings are also accessible for convenience. October 2014 Section 9, Page 57 GDP-32 24

58 GDP INSTRUCTION MANUAL 9.12 NOTES ON FIELD CONFIGURATIONS When running multiple channel receiver systems, you must be very careful to avoid common mode problems. Common mode effects are caused by lack of a reference voltage or level (floating ground), or a reference level that exceeds common mode limits of the input amplifiers. Common mode levels for the standard configuration of the GDP are 10 volts. With isolation amplifiers, this level can be extended to several thousand volts, but in exchange one has to contend with higher noise and a lower overall frequency response. The best configuration that we have found is to install a REFERENCE ELECTRODE (standard copper/copper-sulfate electrode or equivalent), connected to analog ground (COM on the analog side-panel) and the case ground (CASE GND on the side panel), positioned next to the receiver and at least one meter distant from the nearest receiving electrode. This also provides maximum protection from static discharge and nearby lightning strikes. Additional protection in lightning-prone areas can be afforded by using a galvanized iron plate (or equivalent) as a REFERENCE ELECTRODE. This plate should be buried close to the receiver in a hole that has been well watered and the soil mixed to make good mud contact with the plate. Typical size for the plate would be 30 by 30 cm. The following figures provide examples of receiver connections using the REFERENCE ELECTRODE or REFERENCE POT connected to both analog ground (COM) and case ground (CASE GND). We have found that for most environments, the best noise rejection is obtained by connecting the analog ground (COM) to the case ground (CASE GND) on the analog I/O side panel. Note: The GDP-32 II receiver has a captive jumper between COM and CASE GND for the standard configuration. GDP Section 9, Page 58 October 2014

59 9.13 FIELD CONFIGURATIONS TIME DOMAIN INDUCED POLARIZATION PROGRAM GDP as Transmitter Controller with Reference Recording In this application a GDP is used in place of an XMT to control the frequency of the transmitter. At the same time, it is set up with one channel as the reference channel to record the transmitter s current waveform as a time series. The reference GDP will continuously record the current reference while the receiving GDPs will record whatever number of stacks are necessary to acquire good data. All of the stacks are given a time stamp that records the time of the first sample in the time series. When the data caches are processed, the time series segments from the receiving GDPs can be lined up with the long TX reference time series. Note: The GDPs must be synchronized either with GPS, or manually with a MULT/SY-32 SYNC BOX in order to obtain an accurate time stamp in the cache. Refer to Section 6.2, Synchronizing Timing Circuits. In this way it doesn t matter when the receiving GDPs are started and stopped, as long as the TX reference GDP is also recording during this time. WARNING: never connect the reference output of a transmitter directly to a GDP. An ISO Amp must be used to avoid burning out the front end of the GDP analog circuitry. <0913a_CR_TXREF_max_cycs> Make sure Time Series is Yes. Set up one of the channels as the Ref channel. Turn all other channels OFF. Set STACKS to 1. Set SENSE resistor value. (Current will be calculated once first stack is taken) October 2014 Section 9, Page 59 GDP-32 24

60 Set GAIN to MAN Manually set the gain to GDP INSTRUCTION MANUAL Set the frequency. Before transmitting, take one stack with a few cycles to allow GPS sync to occur. Now you can get the transmitter transmitting and adjusted. Take one stack with a few cycles so the reference current will be calculated. Verify the magnitude is not saturating (around 2V). If it is, put in a -1 or a -2 attenuation to bring it below 2V. Use the Scope view to verify the magnitude and that the SP Offset is centered. Manually adjust the SP as needed. SELECT UP Home Move to Cycles field. Press until the maximum number of cycles is reached. <0913b_CR_TXREF_Scope_SP> Note: Press be viewed. to activate and de-activate the Scope while the cursor is on the channel to Note: The TIME field displays the maximum amount of time the reference waveform can be recorded for each stack. WARNING: Whenever the frequency has changed it is best to take one stack with a small number or cycles without the Transmitter transmitting. Whenever the frequency has changed, the first stack will do a GPS sync. During the GPS syncing process, the TX frequencies will change abruptly. At this point, the GDP is ready to acquire the TX current reference waveform time series. The GDP gain and SP has been set up. Once a receiving GDP is ready, the Transmitter should be GDP Section 9, Page 60 October 2014

61 TIME DOMAIN INDUCED POLARIZATION PROGRAM running with the same settings used during setup. The current shown on the GDP should be close to the TX reading, but does not need to be exact. That is why the Current Reference waveform is being recorded. You should start collecting data with this TX reference GDP first, before the receiving GDP. This GDP should be continuously recording the entire time a receiving GDP is collecting stacks. It should only be stopped when the receiving operator is ready to change frequencies. NOTE: It is best to Archive the cache before taking each long time series. Press Enter to start recording the TX Reference Time Series. <0913c_CR_TXREF_ProgBar> Notice the Progress Bar. It indicates how much longer the GDP can collect the continuous time series. In this case, there are about 29 minutes remaining. If the receiving GDP cannot finish its stacks in this time, it is best to stop this time series, archive the cache, and start again. Press Escape to stop recording the TX Reference Time Series. Press Enter to save the data in the cache file. October 2014 Section 9, Page 61 GDP-32 24

62 GDP INSTRUCTION MANUAL GDP Setup for Resistivity, TDIP, RPIP, nrcr <0913d_Setup_IP_GDP_nr> GDP Section 9, Page 62 October 2014

63 TIME DOMAIN INDUCED POLARIZATION PROGRAM GDP Setup with Roll-Along Cable: Resistivity, TDIP, RPIP, nrcr <0913e_Setup_IP_GDP_ra> October 2014 Section 9, Page 63 GDP-32 24

64 Transmitter Setup: TDIP, RPIP, nrcr GDP INSTRUCTION MANUAL <0913f_Setup_IP_Tx_set> GDP Section 9, Page 64 October 2014

65 Transmitter Setup With Current Reference TIME DOMAIN INDUCED POLARIZATION PROGRAM <0913g_Setup_IP_Tx_REF> October 2014 Section 9, Page 65 GDP-32 24

66 Receiver Setup With Current Reference GDP INSTRUCTION MANUAL <0913h_Setup_IP_GDP_ref> GDP Section 9, Page 66 October 2014

67 Laboratory Rock Measurement Setup TIME DOMAIN INDUCED POLARIZATION PROGRAM <0913i_Setup_Lab> October 2014 Section 9, Page 67 GDP-32 24