Identify thermistor?

Reine

Hi,

This isn't Duet related per say but I figured that with so much electronic knowledge here someone might be able to help me out.

Beside my 6HC equipped FDM printer I also have some Formlabs equipment, but my Form Cure has broken down.
It's used to cure resin prints with uv and heat, but it has stopped pre-heating, normally when you start it it shows the chamber temperature until it has reached the target them, usually around 60c. Now though that screen never show, it goes directly to curing and countdown timer. Even after an hour of curing the chamber is barely over ambient temp.

The leads me to believe the thermistor is broken and reports a very high temp so the firmware never initiates the heating element.

I took it apart and found a completely separate thermistor, though without any name beside the jst number on the ring-terminal it was cured into.

I've been in contact with Formlabs support but they don't offer any support or replacement parts, just complete units. Hence I was hoping to maybe be able to diagnose the thermistor and possibly replace it.

I did measure it to around 12k ohm at 22c and after holding it for 30sec it went down to around 11k ohm. If that's normal or not I don't know and was hoping someone here could tell me.

dc42

@Reine said in Identify thermistor?:

I did measure it to around 12k ohm at 22c and after holding it for 30sec it went down to around 11k ohm. If that's normal or not I don't know and was hoping someone here could tell me.

Does the non-working thermistor look like the one you measured?

The one you measured and pictured is probably a 10K NTC thermistor, i.e. its resistance is 10Kohms at 25C. Here's a selection of possibly similar ones: https://www.digikey.co.uk/en/products/filter/ntc-thermistors/508?s=N4IgjCBcpgbFoDGUBmBDANgZwKYBoQB7KAbRAGYBOWagFhAF0CAHAFyhAGVWAnASwB2AcxABfAgA5Y8aCGSR02fEVIgA7OVoAGcoxbtIXXoJGjxIAEyrWACxw8AtnyytCPRqKA.

Reine

@dc42 ohh yeah, those blue Vishay sensors look identical. The one I measured is the one I'm asking if it might be non functional and giving incorrect readings.

So if these sensors read 10K ohms at 25c, it would seam like my sensor is functional then?

dc42

@Reine said in Identify thermistor?:

So if these sensors read 10K ohms at 25c, it would seam like my sensor is functional then?

If it's a 10K thermistor (which would not be unusual for a bed or chamber thermistor) then it is probably functional.

Perhaps there was a problem with the wiring between the thermistor and the controller?