[sdiy] Compensating PTC and NTC resistors

[harrybissell at wowway.com]

I think the idea is that the change of the carbon resistor is so small
compared to the 3900TCR that it could be considered ~linear~

So what you do is to make up a resistor where one portion of the total
resistance is the TCR, and the other fixed... so the overall tempco is
reduced. Its a ~mixture~ problem... maths left to the interested :^)

H^) harry


On Mon, 17 Mar 2008 03:28:11 +0100 (CET), karl dalen wrote
> For example if one finds carbon film resistors having +/-350ppm TCR 
> and metal film +/-100ppm TCR so which one do you use to compensate 
> down the 3900ppm TCR PTC resistor? Obviously you serialize it with a 
> -600ppm resistor. But where do one get a -600ppm metal film 
> resistor? :-)
> 
> KD
> 
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Harry Bissell & Nora Abdullah 4eva