Is Impedance Matching a Concern When Connecting Sensor with NI Modules?

Updated Apr 4, 2019

Reported In

Hardware

  • C Series Sound and Vibration Input Module
  • PXI Sound and Vibration Module
  • C Series Voltage Input Module
  • C Series Voltage Output Module

Issue Details

  • I am using a sound and vibration input module to collect data from an IEPE sensor. Do I need to be concerned about matching to the impedance of my cable to the input impedance of my module?
  • I have a transducer with 50 Ohm input and output impedance, and I saw the NI module has ~1MOhm impedance,do I need to match my impedance.

Solution

No, impedance matching is not a concern when collecting data from IEPE sensors or other transducer when connected to most modules, like the NI-9234 or NI 9775. The maximum sampling rate of these cards is low enough that any reflections that do occur will be negligible. 

Additional Information

Impedance matching is a concern for high-frequency signals that are carried on transmission lines of significant length. The presence of impedance discontinuities or mismatches will degrade the amplitude and phase accuracy, as well as the temporal fidelity, of measurements made with a digitizer. 

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