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.
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 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.
*idnand press ENTER to display the firmware version
helpand 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>
setgaincommand to select a specific measurement range for the voltage (ch0) or current (ch1) measurement channels.
For example, to get help with how to select different measurement display formats, type
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
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.
|Ch1 Gain||Transimpedance||Max. Input Current|
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.
|Ch0 Gain||Gain Factor||Input Voltage Range|
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
Even though 16 gain combinations are possible, most measurements can be performed with the 7 combinations shown in the table below.
|Ch0 Gain||Ch1 Gain||Impedance Measurement Range|
|0||0||100Ω to 1kΩ|
|0||1||1kΩ to 10kΩ|
|0||2||10kΩ to 100kΩ|
These are the same ranges that the autoranging algorithm uses. The following section show how to estimate the impedance value of the DUT to determine the measurement range.
Impedance is defined as the opposition to the flow of alternating current. Admittance is the reciprocal of impedance, or how easy is for alternating current to flow. Electrical components such as resistors, capacitors and inductors have a direct relationship between their value and the expected impedance (Z):
Z = X = -1/(2πfC) for capacitors
Z = X = 2πfL for inductors
Z = R for resistors
Where f is the frequency of the signal; C, L, and R are the component values in Farads, Henrys and Ohms respectively. R represents resistance and X reactance. For admittance (Y):
Y = B = 2πfC for capacitors
Y = B = -1/(2πfL) for inductors
Y = G = 1/R for resistors
Where f is the frequency of the signal; C, L, and R are the component values in Farads, Henrys and Ohms respectively. G represents conductivity and B susceptance.
All components, regardless of their construction, will show a combination of resistive (conductive) and reactive (susceptive) properties. These properties can be expressed in form of ideal electrical components combined either in series or parallel. At any given frequency, impedance/admittance can be expressed as a combination of the reactive element (capacitor or inductor) and a resistive element. The total impedance or admittance magnitude can be obtained by calculating the square-root of the sum of squares (RSS) of the two components or
|Z| = sqrt(R*R + X*X)
|Y| = sqrt(G*G + B*B)
To determine the best measurement range for measurement, it is necessary to estimate the impedance or admittance of the device under test at the frequency of measurement using the equations above. A simpler method to obtain an approximate value based on the expected capacitance or inductance value is through the reactance chart shown below.
To find the approximate impedance or admittance value for a capacitor or inductor, find the closest expected value assigned to the diagonal lines and find its equivalent impedance/admittance value on the vertical axis at the frequency of interest (on the horizontal axis).
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.
To ensure precise and accurate measurements, impedance measurements should be performed with appropriate test fixtures. Measurement leads can introduce additional errors due to parasitic impedances that will vary depending on mechanical configuration.
To ensure repeatable and stable measurements, custom-made fixtures that minimize impedance fluctuations due to mechanical configuration are recommended. For example, to test surface-mount components, fixtures like the B+K Precision TL89S1 or the Keysight 16034G are recommended. For a full list of recommended accessories, please refer to the Recommended Accessories Section at the beginning of this user guide.
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
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.
mdelay (measurement delay) and
tdelay (trigger delay) can be used to control the settling time between measurements.
mdelayis only observed during sweeps and multiple measurements controlled by the “count” command.
tdelay, simply enter the command followed by a value in milliseconds.
When acquiring multiple measurements or performing sweeps, it is useful to plot the results to observe trends or characteristics of the device under test. PuTTY allows the user to copy and paste its screen into a *.csv file that can be opened by spreadsheet applications such as Microsoft Excel®.
To plot the acquired data in Microsoft Excel, follow the steps below:
zcommand to acquire the desired measurements
A few milliseconds after power up, the ADMX2001 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 (ch0 and ch1 gain combination) needs to be calibrated separately. If calibration is performed for only one gain combination, calibration needs to be carried out again if the front-end configuration changes. There are a total of 16 possible gain combinations based on the 4 gain and transimpedance ranges for channel 0 and channel 1 respectively.
To calibrate the module in a specific gain combination, follow the steps below:
calibrate 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.
After completing the steps above, calibration coefficients are generated and stored in RAM. These coefficients will be applied to any subsequent measurements, but will be lost after a power cycle or reset of the module. To store the coefficients in non-volatile memory (flash) the command
calibration commit <date_time> must be executed, where
date_time is the timestamp of the last calibration. For example:
ADMX2001>calibrate commit 11/11/20_10:32
This will store the calibration coefficients in the RAM to the flash, and set the date and time stamp of the calibration to 11/11/20 at 10:32.
Analog123and must be entered after running
calibrate committo save the coefficients. The password can be changed with the
calibrate passwordcommand. Maximum password length is 12 characters.
|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