[Elecraft] Weller WCC100

[David Woolley]

Greg Beat wrote:

> WCC103 temperature sensor has a resistance of about 1 to 2 ohms at
* room temperature (27 C)
> This resistance increases (thermocouple) as the temperature rises --

Thermocouples are voltage source devices, not variable resistance devices.

* the control board then compares this to the temperature set by the user

With thermocouples, you get the difference in the voltage between the 
hot and cold junctions, so, for really accurate operation, you need some 
other mechanism for measuring the cold junction temperature.  In this 
case, the variation in cold junction temperature and required accuracy 
might be low enough that simply assuming 25C is good enough.  Whether 
cold junction compensation is included is a significant feature of the 
design.

* (potentiometer). A "zero-crossing" circuit then turns off the heater

PS I've had to manually wrap the very long lines in this article.



-- 
David Woolley
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