Problem with Thermistor in fast cement

Hi Professionals ,

I got a problem with the Thermistor (100K from RRRF)

If it is hooked up to the Sanguino and not in fast cement just hanging in the air it gives me the room temp of 22 degree.

Now I set up the heater with fast cement an put the thermistor is. It gives me 150 degree whts totally wrong.

So I put it out of the fast cement ant values are correct again.

I really checked that the cables do not touch - so what is the problem do I have to adjust the Termistor?


Greetings from Germany
Alex

The cement is wet and lowering conductivity ?

Hi Alex,

... i think that - either the fast cement is conductive, or you have some additive current through your thermistor what's heating it up, so the reading could be true?

Viktor

If you have multimeter you could connect the thermistor to the multimeter (disconnect from the RepRap elelectorincs) as this will rule out an other sources of the problem. Then if the resistance measured goes down to zero then something is shorting. If it just goes down a few KOhms then it could be the cement conducting.

You need to drive the moisture out of the cement slowly using the instructions here: -

[reprap.org]

It mentions that the moisture will affect the temperature reading until that is done.

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