P a g e 1 ST985. TDR Cable Analyzer Instruction Manual. Analog Arts Inc.

Transcription

1 P a g e 1 ST985 TDR Cable Analyzer Instruction Manual Analog Arts Inc.

2 P a g e 2 Contents Software Installation... 4 Specifications... 4 Handling Precautions... 4 Operation Instruction... 4 TDR Cable Analyzer Block Diagram... 5 Front & Back Panel Items... 6 Initiating the Instrument... 6 Calibration Sequence... 6 Menu Panel... 7 Caution:... 7 TDR cable analyzer calibration... 8 TDR cable analyzer panel... 8 TDR MODE... 9 Clear... 9 TDR... 9 Cap... 9 Loss... 9 TDR... 9 Velocity factor Cable Status TDR General Setup TDR Cap Cable Loss Cable Measurements & Attenuation Loss Display Screen The Timing Panel Utility Panel Reset: Save Plot: Recall Plot:... 14

3 P a g e 3 Save Ref: Recall Ref: Calibrate: View: Print: Help: Other Instruments of ST Oscilloscope Spectrum Analyzer Arbitrary Signal Generator Glossary... 15

4 P a g e 4 Software Installation To install Analog Arts application software, please visit: Specifications To review ST985 specifications, please visit: Handling Precautions Please observe the following precautions while handling your instrument: 1- Do not use this instrument immediately after bringing it from an extremely hot or cold place. 2- Do not expose the instrument to wet or very dusty environments. 3- Do not place liquid-filled containers close to this instrument. 4- Do not use this instrument in strong magnetic fields. 5- Do not apply the instrument to voltages exceeding the maximum rating. 6- Do not connect channel 2 to a live wire before analyzing it with the oscilloscope (channel 1.) Operation Instruction This section contains information needed to operate Analog Arts ST985, TDR cable analyzer and reviews its associated options.

5 P a g e 5 TDR Cable Analyzer Block Diagram The block diagram of Analog Arts TDR frequency analyzer shows a basic representation of this instrument. ST985 is a combination of various instruments including a fast-transient pulse generator, a high bandwidth oscilloscope, and a powerful DSP processor. A signal travels at about 0.7 times (velocity-factor) the speed of light through most cables. While traveling through the cable, if the signal encounters a load not matching its characteristic impedance, it reflects back to its origin. The length of the cable and also its characteristic impedance can be calculated by analyzing the reflected wave. To perform the TDR measurements ST985 applies a fast rising step function to the cable and acquires the reflected wave using a 1 GHz bandwidth signal processing circuitry. Other characteristics of the cable are tested by applying various sine waves with different frequencies at one end of the cable and analyzing the signal at the other end.

6 P a g e 6 Front & Back Panel Items The following diagram shows the position of CH1 (oscilloscope input,) CH2 (TDR input,) TRIG (TDR trigger; internally connected to the SYNC signal of pulse generator,) OUTPUT (pulse generator/ AWG out,) SYNC (pulse generator/ AWG trigger,) and USB connector locations on the panels of ST CH1 input of the oscilloscope; often connected via a probe or coaxial cable to the source input 2- CH2 input of the TDR cable analyzer; often connected to one end of the cable under the test. 3- Trigger (synchronize) input of the instrument, often not connected. 4- Arbitrary waveform generators output; left open when in TDR mode or connected to a cable when in AWG mode. 5- Arbitrary waveform generators sync out; left open when in TDR mode or connected to a cable when in AWG mode. 6- Data transfer LED 7- On/ Off LED 8- USB connector; connected via a USB cable to the computer Initiating the Instrument After installing the Analog Arts software, the Analog Arts icon appears on the desktop. Clicking on that icon initiates the instrument. Calibration Sequence At the start, the device goes through a calibration phase, which takes about one minute to complete. Subsequently a menu panel opens up.

7 P a g e 7 Menu Panel After the calibration process is finished, a menu appears which lists the instruments included in ST985. Pressing on a button in the menu starts its corresponding instrument. To start the TDR click on the "TDR Cable Analyzer". Caution: Before testing a cable of an unknown status, the user should analyze it with channel 1 (the oscilloscope) of the instrument. The standard ST985 is not recommended for live cables.

8 P a g e 8 TDR cable analyzer calibration After the system calibration specific to the TDR is completed, the TDR cable analyzer is ready for testing. This phase takes about one minute to complete. TDR cable analyzer panel The instrument includes several panels as follows: 1- TDR test modes 2- Velocity factor 3- Cable status 4- Cable measurements and attenuation 5- Display screen 6- Timing panel 7- Utility panel

9 P a g e 9 TDR MODE Each measurement is performed by clicking its corresponding button as follows. Clear (1) TDR (2) Cap (3) Loss (4) TDR (5) This button clears all the information on the screen and allows the user to restart a test. The "TDR" button starts the cable length and impedance measurement. In this mode, one end of the cable is to be connected to CH2, with the other end being open. During the TDR test, the screen displays the measuring process, which is analyzing the reflected wave and locating its first occurrence. The "Cap" button starts the cable capacitance measurement. This mode also measures the inductance of the cable. The cap measurement should follow the TDR measurements in the previous step. In this mode (the attenuation mode), the open end of the cable is connected to channel 1 of the instrument, with the other end being open. The "Loss" button starts the cable loss measurement process by applying sine waves at frequencies of 1 MHz, 2 MHz, 3 MHz, 6 MHz, 12 MHz, 24 MHz, and 50 MHz. This mode also measures the resistance of the cable. The button marked "FRA" allows the user to make a comprehensive attenuation analysis and generate a corresponding plot. Please review FRA manual for an overview of the operation of the frequency response analyzer.

10 P a g e 10 Velocity factor This panel indicates the applied velocity factor for the cable. The default value should be changed for different types of cables. Cable Status This panel indicates whether or not the cable is open and or shorted. For shorted cables, it states the location of the short.

11 P a g e 11 TDR General Setup The cable analyzer performs three tests (TDR, Cap, Loss.) These tests must be done according to the following procedure. TDR 1. "TDR" measures the length of the cable and its characteristic impedance. To perform the test, first connect the cable (both the signal path and various conductors of the cable) to channel2, as shown in figure 1. Then, click on the "TDR" button. Cap 2. "Cap" measures the capacitance and the inductance of the cable. Using the same connections as the TDR test, click on the "CAP" button to start the test. Figure 1; "TDR" & "Cap" Setup Cable Loss 3. For the cable loss test, first click on the "Cap" button to turn it off. Then make the connections as shown in figure 2. The resistor R1 value must be equal to the cable impedance found by the TDR test. R2 should have a value of R1 minus 50Ω. For the cable impedance equal or less than 50Ω, R2 is shorted. Once the set up is ready, click on the "Loss" button. The button marked "FRA" allows the user to make a comprehensive attenuation analysis and generate a corresponding plot. Please review FRA manual for a complete overview of the "FRA" features. Figure 2; "Cable Loss" Setup

12 P a g e 12 Cable Measurements & Attenuation Loss This panel displays various information about the cable tested under "TDR," "Cap," and "Loss" modes. Cable Length & Impedance: tabulates the length and impedance of the cable measured in "TDR" mode. The cable length unit is user defined in feet or meters. Capacitance, Capacitance/ft, Inductance: tabulates cable's capacitance and inductance both for the entire cable and also for the specified unit length, tested under "Cap" mode. Resistance, Resistance/ft, Conductance, Loss: tabulates cable's resistance both for the entire cable and the specified unit length, its conductance, and signal attenuation. The attenuation tests are performed under "Loss" mode for 1 MHz, 2 MHz, 3 MHz, 6 MHz, 12 MHz, 24 MHz, & 50 MHz sine waves. The 1 MHz test can be changed to a different frequency between 10 KHz and 50 MHz. The desired test frequency can also be entered in the provided text box.

13 P a g e 13 Display Screen During the TDR test, the screen shows the measuring process, which is analyzing the reflected wave while applying a fast step function at the one end of the cable. In the auto mode, the instrument automatically changes the time setting for the best possible measurements. The two vertical bars on the screen highlight the time duration for the first reflection. The range between green horizontal bars indicate the amplitude of the applied signal. During the process of finding the right set-up, the bars and also the length and the impedance data are given in red color, indicating that the process is not finished yet. During the process and also after the measurement have settled to their final values the screen could provides the overall characteristics of the cable under test. The Timing Panel The timing panel allows for the manual adjustments of the time base to check the uniformity of the cable. It also allows for changing the number of samples for each measurement. The right pointing arrow allows for a longer span of the signal and the left pointing arrow reduces the timing span. Using these buttons brings the instrument out of its automatic mode. To enable the auto setting, simply click on the "Auto" button. The timing panel also allows for changing the number of samples for each measurement. Higher number of samples reduces the noise of the measurement and therefore provides a more accurate measurement.

14 P a g e 14 Utility Panel The utility panel provides the user with various helpful functions listed below. Reset: The reset button resets the instrument to its original settings. Save Plot: "Save Plot" button saves the instrument window in a gif, jpeg, or png format in a user specified location. Recall Plot: "Recall Plot" opens a specified saved plot. Save Ref: "Save Ref" saves a desired screen to be used as reference in future measurements. Recall Ref: "Recall Ref" displays a previously saved reference for comparison purposes. Calibrate: At any time the frequency analyzer can be calibrated using this button. The calibration takes about 60 seconds and ensures the accuracy of the TDR. View: "View" allows the user to change visual settings of the screen such as screen and signal colors to his or her liking. Print: "Print" prints the instrument window by the user specified printer. Help: "Help" opens the Analog Arts' "Help" section, where the user can access view various topics, documentations and or ask his questions from an Analog Arts' application engineer. Other Instruments of ST985 To test for hot wires and or the behavior of the cable under specific condition, ST985 also features a standalone one channel oscilloscope, a spectrum analyzer, and an arbitrary signal generator. Oscilloscope ST985 features a standalone one channel (CH1,) internally triggered 100 MHz oscilloscope with similar specification to the channel 1 of SA915 oscilloscope. Spectrum Analyzer ST985 features a standalone one channel (CH1) 100 MHz spectrum analyzer with similar specification to the channel 1 of SA915 spectrum analyzer. Arbitrary Signal Generator ST985 features a standalone full featured 10 MHz arbitrary signal generator with similar specification to AG815 arbitrary signal generator.

15 P a g e 15 Glossary AC - Alternating Current. A signal that continually changes in potential going from a minimum to a maximum voltage and back. Aliasing - A form of under sampling of a digital oscilloscope in which case the constructed waveform displayed is in the form of a slower frequency of the original input. Amplitude The magnitude of a quantity or strength of a signal. In oscilloscopes, amplitude usually refers to either voltage or power. Averaging A processing technique used by digital oscilloscopes to reduce noise in a displayed signal. Bandwidth The frequency range, here limited by 3 db. BNC - Bayonet Neill Concelman connector; a type of signal connector common in electronic measurement production equipment, used to transmit a signal on a cable. Calibration A process that adjusts offset and gain of signal processing of the instrument. dbm/ 50 - db relative to 1 milli-watt referenced to a 50 Ω impedance. dbm/ db relative to 1 milli-watt referenced to a 600 Ω impedance. dbu - db relative to 1 microvolt, regardless of impedance. dbv - db relative to 1 Volt, regardless of impedance. DC - Direct Current. The electrical voltage that is constant like the output of batteries. Division Measurement markings on horizontal and vertical axis of the oscilloscope. Envelope The outline of a signal s highest and lowest points acquired over many displayed waveform repetitions. Frequency The frequency equals 1/period. Ground A voltage reference usually taken as a point of zero electrical potential, or voltage. Hertz (Hz) - The unit of frequency which is measured by one cycle per second. Marker - Horizontal or vertical visible displays that can be placed across the display panel for measurements or zoom-ins. Noise - A variation in a signal that is (usually) unwanted and conveys erroneous information. Oscilloscope - A device which accepts an electrical input, and represents the variations of the input as a display on a display screen. Peak The maximum voltage level measured from a zero reference point. Peak-to-peak (Vp-p) The voltage measured from the maximum point of a signal to its minimum point. Period The amount of time it takes a wave to complete one cycle. The period equals 1/frequency. Probe An oscilloscope input device, usually having a pointed metal tip for making electrical contact with a circuit element, a lead to connect to the circuit s ground reference, and a flexible cable for transmitting the signal and ground to the oscilloscope. RBW (Resolution Bandwidth) The factor that determines bin size, or the smallest frequency that can be resolved in the spectrum of a waveform. Ringing An undesired effect on a signal resulting from oscillations of circuit resonation.

16 P a g e 16 Sampling The conversion of a portion of an input signal into a number of discrete electrical values for the purpose of processing for display by the oscilloscope. Single Trigger A signal triggered by the by only one a transient event. Spectrum Analyzer - A device which accepts an electrical input, and represents the variations of the magnitude of the input signal versus frequency within the full frequency range of the instrument. TDR Time-Domain Reflectometer; an electronic instrument that uses a technique to track faults in, and or to characterize networks, such as cables. Time Base Oscilloscope circuitry that controls the timing of the sweep. The time base is set by the (n, m, u, -) seconds/division control. Trigger The circuit that references a horizontal sweep on an oscilloscope. Trigger Level The voltage level that a trigger source signal must reach before the trigger circuit initiates a sweep. Trigger Mode A mode that determines how the oscilloscope draws a waveform upon detecting a trigger transient mode. Common trigger modes include normal and auto. Trigger Slope The slope that a trigger source signal must reach before the trigger circuit initiates a sweep. Units - Dimensions of the measured quantities. In oscilloscope units refers to either voltage or time. In spectrum analyzer units refer to either voltage or frequency. Velocity Factor The ratio of actual speed of a wave through a medium, such as a cable, to the speed of light. Volt The unit of electric force or potential difference. Volts (RMS; Root Mean Square) - A unit of voltage equivalent to Volts/ 2 for a sine waveform. Wave a signal that repeats regularly over time, like sine, square, rectangular, saw-tooth, triangle. XY Coordinates x, y intersection points; they are respectively the horizontal and vertical position of a point on the screen display. Zoom a user interface to make the viewing window smaller or larger.