Software Version Hardware Version. TAR-3 Resistance Meter GNSS Mode Manual. Terence W. Andrews

Transcription

1 Software Version Hardware Version TAR-3 Resistance Meter GNSS Mode Manual Terence W. Andrews December 6, 2018

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3 This manual accompanies RM Frobisher (1986) Ltd s TAR-3 Resistance Meter. Please read this manual and the TAR-3 Resistance Meter s manual before using the system. This manual assumes that the user/reader is familiar with conducting a geophysical survey, it only deals with using the TAR-3 Resistance Meter system. Readers are directed to chapter 9 for a suggested reading list of geophysics texts for information on conducting geophysical surveys. This manual is for the TAR-3 Resistance Meter s GNSS Mode function. It assumes that the reader/user is familiar with the TAR-3 System. The GNSS Mode requires additional hardware, which can only be fitted by RM Frobisher (1986) Ltd. If your unit does not contain the necessary hardware you can not use the GNSS Mode. The GNSS Mode reads and stores the NMEA 0183 data strings - the TAR-3 unit does not interpret the information. It stores the data strings on the SD Card with the associated resistance measurements. To interpret the results user s will need suitable software to analyse the data stored on the SD Card. Terence W. Andrews Barnsley, December, 2018 RM Frobisher (1986) Ltd Barnsley Business and Innovation Centre Snydale Road, Cudworth, Barnsley, South Yorkshire. S72 8RP RM Frobisher (1986) Ltd

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5 Contents 1 Conventions and TAR-3 Layout Conventions Used in this Manual TAR-3 Resistance Meter Button Functions Introduction GNSS Mode Overview A Typical Survey Schedule A Few Days Before The Day Before On The Day On site TAR-3 Resistance Meter GNSS Mode GNSS Mode Overview NMEA 0183 Messages GNSS Mode- RS232 Port Measuring Resistance Analysing GNSS Mode Results Using GNSS Mode RS232 Port 15 5 GNSS Mode Operation Continue Session - Option Mark as Dummy - Option RESTART HERE! - Option End Session Now! - Option TAR-3 Data and SD Card Format NMEA 0183 Text File Sample DAT File Output (Binary) Data Structure ( C Code) TAR-3, RS232 Specification 27 8 NMEA 0183 Messages 29 9 Geophysics Reading List TAR-3 Resistance Meter GNSS Mode Packing List 33 5

6 11 Abbreviations and Definitions Used 35 6

7 Chapter 1 Conventions and TAR-3 Layout 1.1 Conventions Used in this Manual To aid the reader and operator of the TAR-3 system the following conventions and nomenclature are used throughout this manual. Warnings Warnings are in bold italic: WARNING! This is a warning! Notes Notes are in bold Note: This is a note. Text Displayed on the LCD Display Text shown on the LCD display: GNSS Mode <= is in a bold sanserif font The is the flashing LCD cursor. When the cursor is visible on the LCD screen the TAR-3 is waiting for the operator to press a button. Text in Capitals Words in all capitals such as ROW, OUT, or ON are used in a restricted manner Words in Bold Capitals Words in bold and all capitals refer to a feature or function of the TAR-3. The following are buttons on the TAR-3 BACK, INC or ENTER 7

8 1.2 TAR-3 Resistance Meter Button Functions The TAR-3 Resistance Meter has ten control buttons (five on each side of the LCD Display). The Left-hand buttons have the same function as the right-hand buttons. They are for left or right-handed users. Figure 1.1: The BACK buttons The BACK buttons scroll back through a list. Figure 1.2: The INC and DEC buttons The INC and DEC buttons change the value of a setting or an option. Figure 1.3: The ENTER buttons The ENTER buttons select an option or confirm a setting Figure 1.4: The NEXT buttons The NEXT buttons scroll/move forward through a list. 8

9 Chapter 2 Introduction 2.1 GNSS Mode Overview The TAR-3 Resistance Meter system is manufactured in the United Kingdom by RM Frobisher (1986) Ltd. using the highest quality components and materials. It contains two Li-Ion battery cells with a total power of 20Wh. At the end of its life it must be disposed of in accordance with the regulations in force at that time. WARNING! The unit must not be burnt or incinerated. The TAR-3 unit contains a modern ARM 32 bit micro controller, advanced digital and analogue electronics to give it superior performance. The TAR-3 Resistance Meter s GNSS Mode consists of an extra PCB mounted inside the TAR-3 Meter s case and an external RS232 connector to connect to a Global Navigation Satellite System (GPS, GLONASS, Galileo or BeiDou) 2.2 A Typical Survey Schedule A Few Days Before Check the TAR-3 unit, do you have all the cables (including the RS232 data cable) and accessories? SD Cards have a habit of going missing over time: they get left in PCs or are reused in other equipment. Put the TAR-3 unit on charge for at least twelve hours or overnight if possible. Note: You must have a SD Card to use the TAR-3 Resistance Meter The Day Before Collect your equipment together and pack it ready for the following day. 9

10 2.2.3 On The Day The TAR-3 is lightweight and robust but it is expensive. It should be transported in the cases/packaging supplied. On hot and sunny days it should not be kept in a locked vehicle. It may be stored in the boot or the rear of a van but consider the security implications of leaving expensive equipment unattended in vehicles On site The TAR-3 unit uses modern zero temperature drift components and software techniques and has zero warm up time. Setting Up The TAR-3 stores the unit s settings on a SD Card. Each time it is switched on it loads the last settings saved. If the previous Session s data was saved on the SD Card the Session No is incremented to the next free Session No (up to a maximum of 99). Users cannot change the Session no (or delete a Session s results) using the TAR-3. Data can only be deleted using a PC. Switching the TAR-3 ON and then OFF does not increment the Session No. Changing the SD Card will change the Session No as this information is stored on the SD Card. If required the SD Card can be swapped between Sessions. (This will change the Session No.) Starting a Session The TAR-3 Resistance Meter is connected to the Global Navigation Satellite System s RS232 data port using the correct cable and the TAR-3 System assembled. Select GNSS Mode and check that the TAR-3 is communicating with the GNSS system. (The GNSS Mode consumes more power than Line Mode or Grid Mode.) When in GNSS Mode battery consumption is very high. A fully charged battery will last for eight hours. Note: When using GNSS Mode make sure that the batteries are fully charged before starting! Packing the Unit Away and Storing If the TAR-3 is to be used the following day it should be recharged ready for use. If the unit is not to be used for weeks, or months, it should be allowed to dry/air before being stored. There is no need to charge the battery before long-term storage. Analysing the Results When the current Session is finished the results are saved to the SD Card and the TAR-3 unit automatically powers off. Switching off extends the battery life and ensures that the results are correctly stored on the SD Card (This is the same as ejecting the card before removing it from a PC.) 10

11 The SD Card can then be removed and the results transferred to a PC for analysis. The results are always recorded in a RAW, binary, format and, optionally, in a plain, ASCII, text file TAR3GNSS.TXT on the SD Card. Note: Do not forget to return the SD Card to your TAR-3. The rest of this manual deals with each of the above steps in detail. 11

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13 Chapter 3 TAR-3 Resistance Meter GNSS Mode 3.1 GNSS Mode Overview The GNSS Mode allows users to take a resistance measurements and log them with the time (in milliseconds) and, if available, the NMEA 0183 string output from the Global Navigation Satellite System device connected to the TAR-3 s RS232 port. The TAR-3 s RS232 Data cable has two connection: Ground and Receive (Rx). The TAR-3 is a NMEA 0183 Listener. The TAR-3 does not Talk to the Global Navigation Satellite System device. The two connections are electrically (galvanically) isolated from the TAR-3 s power supply. 3.2 NMEA 0183 Messages Details of NMEA 0183 messages are given in chapter 8. NMEA 0183 is an electrical and data specification for communication between marine electronics. The data specification of the standard has been adopted by GNSS equipment manufactures. The electrical specification has not been widely adopted by non-marine manufactures. The specification calls for data transmission by EIA- 422, while most manufactures of non-marine equipment have adopted EIA-232 (RS232). Note: The TAR-3 Resistance Meter uses isolated RS232. (With it s own isolated power supply.) The NMEA 0183 specification states that all messages must start with an ASCII (code 0x24) and end with a LF ( code 0x0A). The TAR-3 Resistance Meter starts recording the message when a is received and stops when a LF is received. During data logging it does not check or parse the data. The Receive Time is recorded when the is detected. The frequency of the received messages can be up to ten per second (10Hz). The TAR-3 Resistance 13

14 Meter will accept any message that starts with and ends with a Carriage Return (CR) and Line Feed (LF). Note: "any printable text" CRLF is a valid message The following is also valid NMEA 0183 message. It starts with a and ends with the non-printing reserved characters CRLF. This message has a checksum denoted by the - the check sum has a value of 04 (0x04). GPRMC, ,A, ,S, ,W,3,0,241118,0.0,E,A*04 The TAR-3 does not enforce any message format or check that there is a checksum or that the checksum is valid. During operation the unit displays the age of the NMEA 0183 string. 3.3 GNSS Mode- RS232 Port The TAR-3 s RS232 electrical specification is given in chapter 7. The RS232 port listens for NMEA 0183 messages sent by the attached GNSS unit. During operation the TAR-3 Resistance Meter unit records valid NMEA 0183 messages along with the time from power up and the time the message was received (from power up). The baud rate of the RS232 port can be set to between 4800 bits per second up to 57,600 per second. Note: The maximum data rate is dependent on the cable length and the electrical specification of the transmitting device. Use the minimum speed needed to transmit your desired messages at the frequency required. The maximum supported data rate may change during the day as the ambient temperature changes. 3.4 Measuring Resistance When the Global Navigation Satellite System is attached and communicating with the TAR-3 Resistance Meter users can take resistance readings by lifting theprobesclearofthegroundandinsertingthemintothegroundatthedesired location. The NMEA 0183 data is updated during the reading. 3.5 Analysing GNSS Mode Results RM Frobisher (1986) Ltd. provide software to convert the binary data output of the TAR-3 Resistance Meter to a text file containing only ASCII characters. Users have to provide there own software to analyse their results! 14

15 Chapter 4 Using GNSS Mode RS232 Port Figure 4.1: Select GNSS Mode Press and hold ENTER for three seconds to enter GNSS Mode. Once the mode has been selected (Grid Mode, Line Mode, or GNSS Mode) you can not switch between modes without powering the TAR-3 Resistance Meter off and restarting the Unit. Figure 4.2: Press and Hold ENTER for 3 Seconds The TAR-3 will perform several self tests and pause waiting for the baud rate of the external Global Navigation Satellite System device to be selected. PressINCorDECtochangethesetting,andthenpressandholdtheENTER button down to select it. 15

16 Figure 4.3: Select the Data Speed (Baud Rate) Figure 4.4: Connect GNSS Unit RS232 Cable) There are two LEDS on the TAR-3 Comms PCB. They indicate the status of the RS232 port and connection to the TAR-3 PCB. They are only visible when the rear cover is removed. The Light Emitting Diodes (LEDS) on the GNSS PCB. ❼ No LEDS: The GNSS PCB is not powered up or it is not enabled. Grid Mode or Line Mode selected. ❼ Green LED ON: The RS232 port is powered on and waiting for data. ❼ Green LED Occulting: The RS232 port is active and valid data is being received from the GNSS receiver on the RS232 data line. ❼ Red LED Occulting: The GNSS PCB is powered and data is being transferred to the TAR-3 for logging. ❼ Red LED Off: Error. Pressing ENTER opens the NMEA 0183 data monitoring screen. Figure 4.5: GNSS (GPS) NMEA Data Screen 16

17 GNSS Mode NMEA 0183 data screen has four component sections. 1) Top row, left-hand side: 0C Calc. This is the checksum calculated for the NMEA 0183 data string by the TAR-3 Resistance Meter. The value is in hexadecimal and can vary between 00 and FF depending on the string. 2) Top row, righ-hand side: 0C NMEA. This is the checksum supplied by the Global Navigation Satellite System in the data string. It was calculated by the Global Navigation Satellite System unit and transmitted to the TAR-3 over the RS232 connection. 3) Bottom row, left-hand side: NMEA GPRMC. The NMEA is fixed and unchanging. The GPRMC are the first five characters after the. In this case they are GP for Global Positioning System (GPS) and NMEA 0183 message Recommended minimum specific GPS or Transit data (RMC), Figure 4.5 4) Bottom row, right-hand side: 1.6 The 1.6 is the age, in Seconds, of the NMEA 0183 string. The NMEA display is updated every two Seconds. Depending on the frequency of the transmitted NMEA 0183 data strings (0.5Hz, 1Hz, 5Hz, or 10Hz) the age of the string can vary from 1.9S to 0.1S. Times of 3S, 4S, 5S or above may indicate a problem in the RS232 Data connection. Figure 4.6: GNSS Data Delay Error When the the cable is disconnected the time is OLD! after ten seconds. Figure 4.7: Custom Data MyDat (Without a Check Sum) Not all NMEA 0183 messages have to contain a checksum. Some equipment can transmit custom messages. MyDat is a message transmitted by equipment and is of the form: MyDat,,Some Text,Other information,etc CRLF 17

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19 Chapter 5 GNSS Mode Operation To start GNSS Mode, power up the TAR-3 Resistance Meter and press EN- TER to clear the start up screen and then press INC (twice) to highlight the GNSS Mode <= option. Press and hold ENTER to select GNSS Mode. Select the baud rate and connect the Global Navigation Satellite System equipment. Follow the on screen instructions to check that the TAR-3 unit is receiving the NMEA 0183 data strings. Note: Check that the NMEA 0183 string transmitted by the attached GNSS unit is suitable for your needs. Press the NEXT button. The TAR-3 Resistance Meter will take it s first reading or will display the following screen. Figure 5.1: TAR-3 Insert Probes Screen Figure 5.2: TAR-3 First Reading The first screen, Insert Probes, is displayed when the C1 or C2 probe is NOT in contact with the ground. Inserting the C1 (or C2) probe into the 19

20 ground is the trigger to take a resistance reading. When the probes are inserted into the ground the TAR-3 Resistance Meter takes a resistance reading and displays the result on the LCD screen. Figure 5.2 shows a reading. The LCD display shows: (See Figure 5.2) Ra= 201.5Ω The measured apparent resistance in Ohms. S5 The session number 1/ The reading number 0.6/ The age of the NMEA 0183 data in Seconds RDY A status message - the TAR-3 is ready to take the next reading. Lifting the probes clear of the ground causes the display to change to Figure 5.1, Insert Probes. When the LCD displays Insert Probes the TAR-3 is triggered and ready to take the next reading. This cannot be undone - the only option is to take the next reading. The user takes readings by lifting the probes clear of the ground and then placing the probes into the ground at the desired location. The TAR-3 unit takes a reading and saves it, along with the most recent NMEA 0183 data string to the SD Card. The user continues lifting the probes and placing them in the ground until the area to be surveyed is finished. During the survey session the user can select the following after every reading. By pressing the BACK or NEXT buttons the user can scroll through the previous readings. The text at the bottom right-hand side of the LCD display will change from RDY to VIEW Figure 5.3: View/Review Readings By pressing the INC or DEC button the user can select various options (Opt) to be applied to the displayed reading the options are: Continue Session Mark as Dummy RESTART HERE! End Session Now! 20

21 5.1 Continue Session - Option Continue the session from the last reading Figure 5.4: Options - Continue Session Selecting Continue Session exits the VIEW/Opt functions to return to the last reading and RDY (ready) to take another reading. (An escape, ESC ). A new reading can only be taken when the TAR-3 is ready (RDY) to take a reading. If the user has taken 10 readings, and then scrolled back to reading 5 (As shown in Figure 5.4) Continue Session will update the display to RDY and show reading 5 - ready to take reading Mark as Dummy - Option Mark the displayed reading - flag it. Figure 5.5: Options - Mark as a Dummy Selecting the Mark as Dummy option flags this reading (number 5 as a DMY) After marking as a dummy the value of the reading is unchanged. To take the next reading (number 11) select Continue Session 5.3 RESTART HERE! - Option Restart the Session from the current displayed reading and delete all readings from the reading displayed to the end of the current Session. In this case it will delete readings 10, 9, 8, 7, and 6. The next reading taken will be number 6. This function allows the user to delete readings. 21

22 Figure 5.6: Options - Restart After This Reading 5.4 End Session Now! - Option Finishes the current session at the last reading (number 10 in this example) and saves all of the readings to the SD Card. There are several additional steps before switching the TAR-3 off Figure 5.7: Options - End Session (and Save Results) Confirm the end of the session - press and hold the ENTER button for three seconds to end the Session (Session 4 in this example) Pressing any other button returns to the current Session ready (RDY) to take the next reading. Figure 5.8: Confirm End of Session Users can save the data in a plain ASCII text file or in a compressed binary file. Saving to a text file TAR3GNSS.TXT can take several minutes and is NOT recommended after long data collection sessions containing thousands of readings. Note: Binary data files need to be unpacked see chapter 6 for details. When appending data to the ASCII text file ( TAR3GNSS.TXT ) the LCD display is shown in Figure The cursor at the bottom right-hand corner of the display rotates during the file read and write from to - and back to. It can take several minutes to read all of the data from the swap file and save it to the text file. When the process is complete the TAR-3 unit will switch off. 22

23 Figure 5.9: Save as TEXT File, or Binary File Only Figure 5.10: Saving as a Text File (Cursor) Note: Switching the unit off also ejects the SD Card from the system. Allowing it to be physically removed WARNING! Do not pull the SD Card out of the socket. It is a push in and push to remove socket. Pushing the SD Card releases it and allows it to pop out of the socket slightly. Saving the data in binary format takes 10 Seconds or less. The current Session data is stored in GNSS S00.DAT. When the next Session is started it is renamed GNSS S1.DAT GNSS S4.DAT,..., GNSSS 5DAT, etc. 23

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25 Chapter 6 TAR-3 Data and SD Card Format WARNING! Do not pull the SD Card out of the socket - It is a push in and push to remove socket. Pushing the SD Card releases it and allows it to pop out of the socket slightly. 6.1 NMEA 0183 Text File The TAR-3 Resistance Meter can output the results in plain ASCII text(shown below). It is in comma separated format (CSV). Note: The number of commas after the depends on the NMEA 0183 message and is recorded verbatim from the RS232 data BLANK LINE ++ Start of Session ++ $Session_No=2 # Reading No,Result (in Ohm),Session No,Reading Time(mS), String Time (ms),flag,string Text. 1, ,2, , ,0,$GPRMC, ,A, ,S, ,W,3,0,241118,0.0,E,A*04 2, ,2, , ,0,$GPRMC, ,A, ,S, ,W,3,0,241118,0.0,E,A*0B 3, ,2, , ,0,$GPRMC, ,A, ,S, ,W,3,0,241118,0.0,E,A* , ,2, , ,0,$GPRMC, ,A, ,S, ,W,3,0,241118,0.0,E,A*07 BLANK LINE 6.2 Sample DAT File Output (Binary) The.DAT file contains non-printing characters and can not be edited using an Editor. It has to be unpacked with custom software f0: : f0 ffff 07f0 ffff : f0...X : ffff 07f0 ffff : a... 25

26 6.3 Data Structure ( C Code) struct { uint32 ReadingNo; //4 bytes, Reading number float Reading ; //4 bytes The measured value in Ohms uint32 SessionNo; //4 bytes Session No uint32 Flags; //4 bytes 1=DMY, 0=VALID (Other values are reserved) uint32 ReadTime; //4 bytes Time in ms from power on uint32 ReceiveTime;//4 bytes Time in ms from Power on uint8 String[88]; //88 bytes The GNSS string inc. $, checksum terminated with `\0' int32 TARUSEONLY; //4 bytes TAR-3 internal use (unpack but do not use) } Result; // ReadTime - StringTime is the age of the GNSS string in ms Using Perl it can be unpacked using unpack("lflllla88l", buffer) 26

27 Chapter 7 TAR-3, RS232 Specification Table 7.1: TAR-3 Resistance Meter- RS232 Electrical Specifications Input (Rx) Maximum Voltage +25V and -25V Input Impedance 5000 Ohms Low Less than 2.0V High Greater than 2.1V Output (Tx) Output Voltage +5V and -5V (Min) Output Impedance 300 Ohm Table 7.2: TAR-3 Resistance Meter- RS232 Data Specifications Baud Rate None, 4800, 9600, 18,200, 38,400, 48,000, 57,600 Data length 88 bytes (characters) Transmission 8 bits, No parity, 1 stop bit (8,N,1) 27

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29 Chapter 8 NMEA 0183 Messages The National Marine Electronics Association (NMEA) regulate and promote the NMEA 0183 standard (and later updated versions) Information can be found on their website at < The NMEA 0183 specification requires that all of transmitted data are printable ASCII characters between 0x20 (space) to 0x7e ( ). There are also the following reserved characters. Table 8.1: NMEA 0183, Reserved Characters ASCII Hex Dec Description CR 0x0d 13 Carriage return LF 0x0a 10 Line feed, end delimiter 0x24 36 Start delimiter * 0x2a 42 Checksum delimiter, 0x2c 44 Field delimiter Messages have a maximum length of 82 characters, including the starting character and the ending LF The start character for each message is a (for conventional field delimited messages). The next five characters identify the talker (two characters) and the type of message (three characters). All data fields that follow are comma-delimited. Where data is unavailable, the corresponding field remains blank (it contains no character before the next delimiter). The first character that immediately follows the last data field character is an asterisk, but it is only included if a checksum is supplied. The asterisk is immediately followed by a checksum represented as a two-digit hexadecimal number. The checksum is the bitwise exclusive OR of ASCII codes of all characters between the and *. According to the official specification, the checksum is optional for most data sentences, but is compulsory for RMA, RMB, and RMC (among others). CRLF ends the message. 29

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31 Chapter 9 Geophysics Reading List Seeing Beneath the Soil: Prospecting Methods in Archaeology Clark, O.A., Clark, A., , 2003, Taylor & Francis. Revealing the Buried Past: Geophysics for Archaeologists Gaffney, C.F., Gater, J., , Revealing history, 2003, Tempus. Earth Resistance for Archaeologists Schmidt, A., , Geophysical methods for archaeology, 2013, AltaMira Press, GPS for Land Surveyors Van Sickle, J , Geophysical methods for archaeology, 14 July 2015, CRC Press; 4 th edition 31

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33 Chapter 10 TAR-3 Resistance Meter GNSS Mode Packing List 1. In addition to the TAR-3 Resistance Meter system with Comms PCB fitted, 2. TAR-3 Resistance Meter to GNSS Equipment RS232 Data Cable (Bare ends) 3. This manual. 33

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35 Chapter 11 Abbreviations and Definitions Used 35

36 Table 11.1: List of Abbreviations and Definitions GNSS Global Navigation Satellite System BACK (Button) Allows the user to scroll backwards through the menu or readings BIN A file extension for file with binary data (you can not read the contents directly. Binary The RAW output from the TAR-3 DAT A file extension for file with binary data (you cannot read the contents directly.) DEC (Button) Allows the user to decrease (change) the displayed setting/option DMY Short for Dummy Dummy A reading who s value is to be ignored ENTER (Button) The ENTER button (SELECT the current option) INC (Button) Allows the user to increase (change) the displayed value or option NEXT (Button) Allows the user to scroll forwards through the menu or readings OFF Button Powers the TAR-3 1 off without saving data or settings ON (Button) The ON button below the LCD display RESET (Button) The button on the rear of the TAR-3 that switches it OFF SELECT The ENTER button also selects the displayed option SET The Settings file extension (containing a copy of the current settings) TXT The file extension for a file containing human readable information 36