SV: [sdiy] Compensating PTC and NTC resistors

[karl dalen]

--- Paul Perry <pfperry at melbpc.org.au> skrev:

> There is no point obsessing over this.

Paul! 
Would you mind not putting-words-in-my-mouth, its the third time you do this!
Its tiresome!

> 
> Given the range of specifications for the PTC resistor, if you want
> precision, you will have to tweak the final unit, while raising and lowering
> the temperature of the circuit. Not easy at all.

As mentioned previously (and many years ago) ppm of PTC are not
linear by temp nor by voltage or load. At least of there hasent 
been some new tech coming around. 
 
> Using a metal film resistor to tweak the coefficient of the PTC, will get
> you closer to the ideal world. Whether its own coeff is +100 or -100.

So! What if the coefficient are +/-1500?

For your information MFR (example) actually needs burn in for 5000hours
to be within TC spec.Go figure where it are if not burned in.

KD


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