@dc42 yeah it is only ever the bottom sensor that exhibits that behavior. I am fairly confident my connector crimps are good as I have tried to shake/shimmy the harness around while heated and attempted to recreate the readings but they were stable. I just hate that the problem is so inconsistent and hard to replicate. I will start by replacing the sensor and double checking my connections on both sides and see if that fixes the issue.

Thanks for putting up with the troubleshooting. Glad it's working now.

@Phaedrux
Thank you

@dc42 said in PT100 failure lesson learned:

Temperature inaccuracies when using PT100 sensors are usually caused by poor connections. Each ohm of resistance in the connections or the cable will increase the reading by about 2.5C. I have this problem on one of my owm printers at present, I can make the reading change by more than 10C by waggling the cable close to one of the connectors.

Hmm, well I swapped with my other PT100 sensor and printing was transformed back to normal? I ordered another one tonight. Once I have 3 I may mess around with them.

If you use long wires, or you will have connectors in the cable, then 4 wires is best. If the cable is short with no connectors except where you connect it to the PT100 and the daughter board, then 2 wires is sufficient.