NTC Thermistor noise disturbance

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funnyKedougou

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Hello, I am new in this community and I am glad to a membre.
Actually I am bloked since almost 1 mouth on a problem. Look at the circuit below


the NTC thermistor returns wrong values due to disturbance coming from nearby MOSFET. see below

I tried to create a filter by changing the C105 value to 200n or to add a 10k R to create a PI RC filter. But noise reduced but stay high.

Can please give some new ideas ?

Thanks
 
funnyKedougou said:
I tried to create a filter by changing the C105 value to 200n or to add a 10k R to create a PI RC filter. But noise reduced but stay high.
Click to expand...
Is the filter close to the MOSFET input, where it should be?
Have you tried increasing the value of the capacitor?
 
Yes the CTN and RC very close to the Mosfet, the reason is to have better measure of the Mosfet heating.
increasing the C105 value was my first idea, but this reduce the noise just a little.
 
Your circuit shows it having a ground remote to the MCU. If it wired like that, it could well be ground noise.

Try power and ground connections directly at the MCU, and no connections to anything else away from the MCU.
 
I have used 3 values: 10n, 222n (100+100+22n) and 400n (200+200n). In the final try, I added a 10k R and I have now a better result but not good yet :-I
 
funnyKedougou said:
I have used 3 values: 10n, 222n (100+100+22n) and 400n (200+200n). In the final try, I added a 10k R and I have now a better result but not good yet :-I
Click to expand...
You can go a lot higher than that since the thermistor resistance changes slowly, so even a large RC value won't affect the measurement accuracy.
 
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