Create compensation values to account for the impedance of cables, connectors, and other components in the measurement path. Create compensation values for EIS tests and ACIR tests.

The compensation value is subtracted from the impedance that is obtained during the test. The resulting value is the impedance of the battery cell.

If you have multiple instances of the same DUT, create one compensation file for all DUTs. Create or update a compensation file when you complete any of the following actions:

  • Change the excitation current
  • Add more frequencies to the frequency sweep
  • Change the maximum or nominal voltage
  • Move or adjust the cabling to the fixture
  • Re-cable or replace the fixture
  • Change the SMU that is taking the measurement
Note You are not required to recalculate the compensation values if the SMU runs self-calibration.
Before you begin, create a configuration file for the EIS test or the ACIR test.

Equipment

  • PXIe-4139
  • Compensation device in place of the DUT
  1. Use the NI Example Finder to open <Test type> Create or Override Compensation Files.vi.
    1. In the LabVIEW window, select Help » Find Examples.
      The NI Example Finder window loads.
    2. Select Toolkits and Modules » Battery Cell Quality » <Test type> Create or Override Compensation Files.vi.
      The front panel of the VI loads.
  2. On the front panel of the VI, select the SMU resource from the HW Resource Name and Channels control.
    Note NI supports the PXIe-4139 (40 W) and PXIe-4139 (20 W) SMUs.
  3. Optional: If you want the SMU to perform self-calibration, enable self-calibration on the front panel.
    Note You must disconnect the DUT during self-calibration. If the DUT is connected to the SMU during self-calibration, an error occurs.
  4. Update the test parameters input to use the same settings you use for the test.
    If you are using a configuration file, you must specify the same Compensation Method when creating the configuration file.
    OptionDescription
    Enter the test parameters for an EIS test.
    1. Configure the Frequency Sweep Characteristics. Each entry on the Frequency Sweep Characteristics array defines the parameters that the VI uses to generate a sine wave. Refer to Configuring the Frequency Sweep Characteristics for EIS Measurements for more information about each parameter.
      1. Select the number of tests.
      2. Select the Frequency (Hz). The frequency is limited by the number of arrays you selected.
      3. Select the Current Amplitude (A).
      4. Select the Number of Periods.
    2. Select the Voltage Limit Hi (V).
    3. Select the Nominal DUT Voltage (V).
    4. Select the Compensation Method.
    5. Select the Power Line Frequency.
    Enter the test parameters for an ACIR test.
    1. Select a Nominal DUT Voltage (V).
    2. Select a Voltage Limit Hi (V).
    3. Select a Current Amplitude (A).
    4. Select a Number of Periods.
    5. Select a Compensation Method.
    6. Select a Power Line Frequency.
  5. Optional: Select a Known Impedance Table.

    If you select Short Compensation for the compensation method, you can use a small known resistor in the jig as a compensation device. Define a Known Impedance Table. Then, provide the path to a Known Impedance Table so that the compensation file records only the difference from the known values. The saved compensation reflects the impedance of the jig, which must be compensated during measurement.

  6. Place the short compensation device in the fixture.
    Note NI does not provide a compensation device. You must design and create a device that is based on the guidelines provided in Improving Measurement Accuracy with Compensation.
  7. Click Run.
    The VI creates a file of compensation values in the following folder: C:\Users\Public\Documents\National Instruments\NI-Cell Quality\Compensation.

    The compensation file name has the following structure: z_Short_<smu-serial-number>_Ch0.json.

When running EIS tests and ACIR tests, verify that you selected a compensation method in Obtain Test Parameters.vi.