On 10/03/2016 13:42, Adrian Caspersz wrote:
On 10/03/16 07:23, mike wrote:
I have an Ungar 9911 soldering iron handpiece
without the controller. Looks new.

I thought it would be trivial to build a temperature
controller.
I can make it hot. There is some PTC going on
as the current goes down as the iron heats up.

I expected some feedback.
The only other connector pins that have some
connectivity measure 497 ohms independently of
temperature. Can't use that for temperature monitoring.

Google has failed me.
Anybody know how these work?

Probably it's a diode, and an auto-ranging DMM showing forward voltage
not resistance.

e.g.

http://www.tmatlantic.com/upload/akt...Diode_Test.jpg

Try reversing the test leads?



Diode would make an excellent temp sensor, but you would have it right
at the duty end, for minimum time-lag, are there high-temperature diodes
? or a way to have a fast-response normal diode set in a
thermal-conductance scaled-down insulated sub-housing?