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Faulty temperature sensor

i don't know but do you mean 2 wires or 2 cables? there is a difference. cables have 2 or more wires and even conductors like drain wire. wire on the other hand is a single conductor with some kind of insulation around it. in any case. it's hare to say what type you have ?., could be a Type-J, in many cases i have seen 2 sets of these types wrapped around heating tubes. only 1 needs to be used, in any case they are very small conductors and mostly the J type which is 2 unlike metals twisted and electrically bonded together. the idea is when its heating one wire will contract more than the other causing tension forces which produce a small amount of current to the ratio of heat. with these types you need a HI-Z micro volt meter to see the voltage coming out of it. some 10Meg-Z DMM's have a low scale that will read it. under an ohm meter it will appear to be shorted.

-- now the RTD types ( Resistor thermo device). that is basically a resistor that decreases in value as the temp goes up. these was have 2 wires

--
  then you have the IR (infra Red), where light is used to generate an
effect with a IR detector since temp produces  IR in most cases that i
know of..
  those comes in a different variety.. , modular types which require a 
gnd, Vcc and 2 optional outputs.
  some times it just a simple IR diode with a lens which only have 2
wires.
so take your pick..
  P.S.
    the Twisted Wire types normally use the same type of
material as the lead wire to the controller.
Reply to
Jamie
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Hello,

I would like to check out a temperature sensor for my central heating cylinder. 2 cables coming from the sensor.

What voltage do I need? What should change with the rising temperature?

Thanks.

Reply to
Jurgen Bauer

Thanks for the detailed explanation. I'm working with a Micrel MIC280 and it use a 2N3906 transistor junction as its remote sensor. Micrel has a demo board and software that runs off a PC's printer port and you can set "high" and "low" level trip points.

I'm working on a USB temp controller with multi-zone sensor inputs based around the MIC280. Its been a fun project.

Reply to
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