[sdiy] Compensating PTC and NTC resistors

Barry Klein Barry.L.Klein at wdc.com
Tue Mar 18 18:01:17 CET 2008

I entered the Microbridge rejustor contest with an entry discussing the use
of their etc-rejustor for this purpose.  I tried my best, but I am no
"rocket-scientist":  it looks like this part or a derivitive could be used
to electronically/methodically "dial in" the tc.  I gave up on math years
ago so the nitty gritty of this stuff is just beyond me and I can live with

Hopefully I'll get a mini-cooper out of it...?  I don't know - they were
supposed to pick winners in January and still have not.


-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Paul Perry
Sent: Monday, March 17, 2008 7:27 PM
To: Synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Compensating PTC and NTC resistors

There is no point obsessing over this.

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.

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.

If you want to do better, then you can use a thermostatically controlled
oven - or you can make a micro sized oven, using the transistors on a chip
system invented by Jim Williams.

Note that a PERFECT synth, would be as stable as a digital one - I'm not
sure everyone would want that ;D

Paul perry Melbourne Australia

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