RTDs are extremely reliable temperature sensors. However, when they do fail, the failure modes can be typically broken down into the following categories:
When RTDs exceed their designed temperature limits, the wire insulation materials in the stem will start to break down. This can result in electrical shorts and resistance errors. It can also create pinholes in the stem and cracks in the potting sealing the stem. When the stem integrity is breached, moisture can then get in and cause resistance errors.
Corrosion will often result in pinholes and pits in the stem. Once the stem is no longer sealed, moisture and the process can penetrate the stem causing resistance errors and electrical shorts. Some solutions to corrosion include thermowells or Teflon coated stems.
Extreme vibration fatigues and strains wires and welded connections inside the sensor assembly. This can result in resistance errors as well as connection breaks. Reotemp’s solution to this failure mode is the unique Hi-Vibe™ option for vibration applications.
Some examples of user abuse include wires shorted out from being twisted together or corrosive media being allowed into the RTD assembly head.