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The EVAL-ADMX2001EBZ is an easy-to-use evaluation and development board that enables convenient access to the functionality of the ADMX2001 Precision Impedance Analyzer Measurement Module.
There are five simple steps to start evaluating the ADMX2001:
These steps are explained in detail in the following sections.
Installation steps:
To communicate with ADMX2001 via its command-line interface and UART, a terminal emulator like PuTTY is recommended. Visit the URL below to download PuTTY
Download the MSI (Windows Installer) and execute it. Follow the on-screen instructions.
The following figure shows the basic connections required for evaluating the ADMX2001.
*The switches S1 and S2 must be set to DUT and GND respectively to connect the ADMX2001 to the BNC terminals.
After installing PuTTY, select the Serial connection session, and configure the Serial category as shown below. Please note that the COM port must match the COM port number selected by the driver in the previous step.
Make sure the hardware is properly installed and that power is available to the board via the 12V power adapter. Then, simply “Open” a serial connection to initiate the session. PuTTY will launch a blank window.
*idn
and press ENTER to display the firmware versionhelp
and press ENTER to see a list of commands supported by ADMX2001.For a complete list of ADMX2001 configuration parameters please refer to the ADMX2001 Configuration Parameters section in this page. For a complete command set reference, please refer to the Command Set Reference section in this page.
Please note that closing PuTTY's terminal window does not reset the ADMX2001 settings from the last session.
Upon opening a session with PuTTY, the ADMX2001 is ready to perform impedance measurements.
By default, the module is set to perform single-point measurements with a 1VRMS signal (1.41 signal magnitude) at 1kHz, and no dc offset. To initiate a measurement type the z
command at the prompt and press ENTER.
Perform a capacitance measurement in parallel with an equivalent resistor (Cp-Rp) at 100kHz with a 1V amplitude sine. Return 5 readings, where each is an average of 10 samples.
ADMX2001> frequency 100 frequency = 100.0000kHz ADMX2001> display 9 Measurement model: 9 - Capacitance and equivalent parallel resistance (Cp,Rp) ADMX2001> magnitude 1 magnitude = 1.0000 ADMX2001> average 10 average = 10 ADMX2001> count 5 sampleCount = 5 ADMX2001> z 0,5.677640e-13,8.062763e+07 1,5.668012e-13,8.305672e+07 2,5.675237e-13,8.208995e+07 3,5.673763e-13,8.276912e+07 4,5.683635e-13,8.463327e+07 ADMX2001>
setgain
command to select a specific measurement range for the voltage (ch0) or current (ch1) measurement channels.
The help
command will display all the commands available to the user from the command-line interface (CLI).
To get help for any command, simply type
ADMX2001>help <command>
For example, to get help with how to select different measurement display formats, type
ADMX2001>help display
Which should show a similar screen to the picture shown below
This section presents common measurement use cases.
By default, the ADMX2001 is in auto-ranging mode, which will optimize the measurement gain of the voltage and current measurement channels, depending on the frequency and magnitude of the test signal.
In some cases, the user may want to select a specific measurement range. The measurement range is mostly affected by the transimpedance of channel 1 and the test signal magnitude. It is recommended to select the transimpedance value that is smaller than the expected value of the impedance under test, but larger than the next transimpedance selection.
For example, if the DUT's expected impedance value is 2kΩ, enter the following in the command line prompt
ADMX2001> setgain ch1 1 Current meas gain = 1
The command setgain ch1
will set the transimpedance of the L_CUR input (channel 1) to 1kΩ. It is not recommended to use the 10kΩ value since this could exceed the input channel measurement capabilities and return incorrect readings.
The transimpedance values available are listed below.
Enumeration | Transimpedance | Max. Input Current |
---|---|---|
0 | 100Ω | 25mA |
1 | 1kΩ | 2.5mA |
2 | 10kΩ | 250uA |
3 | 100kΩ | 25uA |
The command setgain ch0
modifies the input voltage range of channel 0 (between terminals H_POT and L_POT). This is less common, but it can be used to improve measurement sensitivity if the impedance under test is smaller than the lead impedance or less than 100Ω. It can also be used if the magnitude of the test signal is small. This can be the case with sensitive loads, or when the test frequency is high.
Available voltage gain values for channel 0 are listed below.
Enumeration | Gain Factor | Input Voltage Range |
---|---|---|
0 | 1 | 2.5V |
1 | 2 | 1.25V |
2 | 4 | 625mV |
3 | 8 | 31.3mV |
Typing the command setgain
will display the gain of both input channels and whether or not autoranging is enabled.
ADMX2001> setgain Autorange enabled voltGain = 1 currGain = 3 ADMX2001>
To turn autoranging back on after setting a manual range type setgain auto
The average
command determines how many samples are averaged for each reading returned. Averaging reduces noise and is helpful in applications that require to detect small changes in a value or when the impedance component of interest is small in comparison to the total impedance magnitude (e.g. ESR of capacitors). The default is set to 1, which means that no averaging is done.
The ADMX2001 can automatically perform measurements that sweep different measurement parameters such as
By default, the sweep function is off. To enable parametric sweeps, use the sweep_type
command and specify the sweep type. The command also requires to enter the start and end points of the sweep. The number of points is determined by the count
command.
Perform an 11-point logarithmic frequency sweep from 100kHz to 1MHz.
ADMX2001> count 11 sampleCount = 11 ADMX2001> sweep_type frequency 100 1000 Frequency sweepStart = +100.0000KHz sweepEnd = +1000.0000KHz ADMX2001> sweep_scale log Sweep scale is log ADMX2001> z 1.000000e+05,5.683433e-13,8.149236e+07 1.258925e+05,5.704062e-13,4.727518e+07 1.584893e+05,5.674423e-13,2.989029e+07 1.995262e+05,5.652225e-13,1.917354e+07 2.511886e+05,5.622380e-13,1.233886e+07 3.162278e+05,5.577508e-13,8.082886e+06 3.981072e+05,5.490229e-13,5.611289e+06 5.011872e+05,5.421543e-13,3.547964e+06 6.309573e+05,5.299540e-13,2.360688e+06 7.943282e+05,5.136760e-13,1.624230e+06 1.000000e+06,4.798023e-13,1.411488e+06 ADMX2001>
The DC resistance measurement function can be easily selected by setting the test frequency to zero.
ADMX2001> frequency 0 DC Resistance mode enabled ADMX2001> z 0,6.834371e+01 ADMX2001>
In the DC resistance mode, only the dc resistance value is returned.
The commands mdelay
(measurement delay) and tdelay
(trigger delay) can be used to control the settling time between measurements.
mdelay
is only observed during sweeps and multiple measurements controlled by the “count” command.
To setup mdelay
and tdelay
, simply enter the command followed by a value in milliseconds.
After booting up, Wildcat is ready to perform measurements. However, any readings and their units are scaled and assigned using nominal circuit parameters. Measurement accuracy can only be evaluated after performing calibration on the module with an external calibration source with certified traceability. There are three basic calibration steps involved in calibrating the module: open calibration, short calibration, and load calibration. The first two correct the module and test lead parasitics. The latter provides traceability to an external source. Each measurement front-end configuration (or gain combo) needs to be calibrated separately. If calibration is performed in only one gain combo, calibration needs to be carried out again if the front-end configuration changes. There are a total of 16 possible configurations based on the 4 gain and transimpedance combinations for channel 0 and channel 1 respectively. At this time, calibration is not persistent after power cycling or reset. To calibrate the module in a specific gain combination, follow the steps below: 1. Setup Wildcat in the desired measurement configuration 2. Set the averaging to 200 samples and tdelay to 200ms (to allow sufficient settling time). 3. Connect the H_POT and H_CUR terminal together and the L_POT and L_CUR terminals together to form two separate connection pairs a. Run the “cal open” command 4. Connect all the measurement terminals together. a. Please note that this step is only required if the short-circuit path impedance is significant compared to the impedance under test b. Run the “cal short” command 5. Connect known impedance between the measurement leads as shown in Figure 3. a. Run the “cal rt <value1> xt <value2> command where <value1> is the true value of the resistive component of the calibration impedance and <value 2> is the true value of the reactive component.
Terminal | |
---|---|
H_CUR | Signal source terminal. It generates the excitation required for measurement. This terminal can source up to +/-5V @ 50mA |
H_POT | Voltage sense terminal. Connect to H_CUR at the device under test (DUT) |
L_POT | Voltage sense terminal. Connect to L_CUR at the device under test (DUT) |
L_CUR | Current sense terminal. Return path for the excitation signal. Connect to the opposite end of the DUT as H_CUR |
UART TX | UART transmitter pin. Connect to RX pin on the UART to USB cable |
UART RX | UART receiver pin. Connect to TX pin on the UART to USB cable |
UART GND | UART ground. Connect to ground pin on the UART to USB cable |
CLK_SEL | Jumper selection of internal or external clock. Set to internal for default operation |
TRIG_IN | Trigger input. Use for hardware-timed acquisition only, otherwise leave disconnected (future expansion) |
TRIG_OUT | Measurement complete trigger out (future expansion) |
CLK_IN | External clock input. Use a LVCMOS 50MHz clock signal and set CLK_SEL to EXT position |
CLK_OUT | Clock output. These two terminals have a buffered replica of the 50MHz master clock |
PMOD | Master and slave PMOD terminals for SPI port (future expansion) |
*Arduino headers currently reserved for future expansion
This section describes the commands available through the command-line interface (CLI).