Compensating Passive Probes

Compensating passive probes increases the accuracy of your measurements by matching the capacitance of your probe to the capacitance of a particular oscilloscope input channel.

Note For more information on using InstrumentStudio, refer to the InstrumentStudio Manual at ni.com/manuals.
To compensate a passive probe, complete the following steps:
  1. Connect the ground clip of the probe to the ground terminal on the front of the oscilloscope.
  2. Connect the ground clip of the probe to the ground terminal on the front of the oscilloscope.
  3. Contact the tip of the probe to the 5 V square wave terminal on the front of the oscilloscope.
    Note The probe compensation signal at this terminal is activated by default on the PXIe-5110/5111/5113. You can disable and re-enable the signal in InstrumentStudio with the Probe Compensation options in the instrument header menu (1378) in the upper-right corner of the panel or programmatically in NI-SCOPE with Probe Compensation Signal Stop and Probe Compensation Signal Start.
  4. In InstrumentStudio, configure the settings of the input channel to which you connected the probe.
    1. Set the channel to On to display the signal.
    2. Set the Input impedance of the channel to 1 MΩ.
    3. Set the Vertical offset to 2.5 V.
    4. Match the Probe attenuation setting to the setting on the probe.
  5. Adjust the vertical range on the input channel until the signal starts to clip and then increase the vertrical range by one step so that it no longer clips.
    This process ensures you are using the maximum dynamic range of the ADC.
  6. Examing the digitized signal and adjust the tunable capacitor on the probe.
    The probe is correctly compensated when the waveform appears as square as possible:
    1378

Once compensated, the probe conveys signals to the input channel accurately, without artificially attenuating or amplifying frequency components of the signal.
Tip For the most accurate measurements:
  • Compensate probes for each channel of the oscilloscope;
  • Use a compensated probe only with the channel you used to compensate it; and
  • Compensate your probes frequently.