Temperature sensor for induction motor case and stray magnetic fields

[e100]

Are temperature sensors such as thermistors, RTDs or the DS18B20 affected by the stray magnetic field from an induction motor when mounted on the exterior aluminium heatsink?

I only need 1 degree C resolution. Can I just use them like normal, or do I need to synchronise the readings in time with the magnetic field  to get consistent values?

[SeanB]

No, you just need to ensure that the wiring is twisted and no large open loops to induce AC voltage into it. Shielded twisted pair cable is easiest to use, though almost all of the motor protection sensors are just twisted pair high temperature wire inside the motor itself, and you generally in any case want to do averaging over a few readings as well, reduces noise in all cases.

[Richard Head]

Also, ensure that there is minimal capacitive coupling between the sensor and the motor frame. If they share the same ground it shouldn't be a problem but if the circuitry is floating wrt to AC earth then it may be a problem.  Maybe a good idea to add some hysteresis to the switching point so when the motor overtemps it doesn't re-start 15 sec later.