Temperature Impact on Passive Probes

Question: What can happen when I exceed the operating temperature range of a passive probe?

Answer:  Employing a passive probe outside of its rated operating range may cause any or all of the following:

  • Safety regulations violation, destruction of the probe or the circuit under test, or measurement inaccuracy could all result.
  • Burnout of the probe head resistor could occur at a combination of high temperature and high voltage due to power dissipation heating plus ambient temperature.  A burnout could also potentially cause a fire.
  • Parts could come apart or break at high or low temperatures that are outside of the rated operating temperature range.  This is due to the temperature in combination with physical stress (such as tension, bending, compression, or probe motion/vibration), and the characteristics of the adhesives and materials used in the probe.
  • Even if there is no mechanical stress on the probe, multiple repeated temperature swings over the non-operating temperature range could cause parts to break, and adhesives to fail.
  • If the probe comes apart, the probe ground could contact a non-grounded part of the circuit, causing damage or fire.

Measurement inaccuracy could occur due to high or low temperature, causing a change in the resistor value, or capacitor value of the parts in the probe head; or a change in the dielectric constant or dielectric loss of the coax cable.

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