[D.I.Y. tempco sensors]

[Mike I]

Hi Harry,
I measured the resistance of three  DIP relays (same part number, 1000 
ohm coils) and found they were not more than 50 ohms off the mark. 5 
percent is not bad. Putting them in the refrigerator for 1 hour along 
with a digital thermometer probe dropped the temperature by 23 C. Taking 
them out and measuring the resistance quickly gave the expected result 
for a +3900 ppm tempco. I imagine the inductance is probably a few 
millihenries. Used as a passive voltage divider this should give no 
problems. Maybe if audio-rate FM was being done with the VCO by feeding 
in a square wave it would high pass filter the modulation signal. Let me 
know how it works!  Mike I.