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Topic: what temp sensor do i have? (Read 543 times) previous topic - next topic

TECH GEEK

ok so i opened up a digital thermomiter hopping to find a LM35 but all i found was a blue, 2 pin, sensor...
i would like to know how to use it with a arduino, but all i can figure out is it is basicly a temp-controled potentiomitor, and that would mean i can not find it's total value without either a datasheet or puting it in an oven/freezer at it's maxium & minimum ratings and mesuring it's ohms
any idea as to how i can find more about it? like a datasheet hopefully? and no #'s or letters on it at all...
As always... Thanks for posting!!!

RuggedCircuits

It's probably a thermistor. Without markings you are probably going to have to characterize it at some know points (room temperature, fridge temperature, freezer temperature, body temperature) then measuring the resistance, as you say.

If it is a thermistor it's easy to use with an Arduino, just make it one resistor of a voltage divider.

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

GaryP


ok so i opened up a digital thermomiter hopping to find a LM35 but all i found was a blue, 2 pin, sensor...
...
i can not find it's total value without either a datasheet or puting it in an oven/freezer at it's maxium & minimum ratings and mesuring it's ohms
any idea as to how i can find more about it?


Make it easy way, just like you say. Measure it when you know the correct temperature, and do it in many different temperatures.
It is a thermistor.

Cheers,
Kari
The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"

liudr

#3
Apr 04, 2011, 06:27 am Last Edit: Apr 04, 2011, 06:31 am by liudr Reason: 1
First of all, a thermistor costs like $0.40 a piece if you buy 10 or 20 at a time so even if you can't figure out the factors, not big deal, buy some that come with spec sheets. If you want to determine the spec of your blue thermistor, you need to measure at least two temperatures., 25DegC and something like 80DegC if it's not too hard to do.

Set 25DegC and measure resistance gives you R1, then set at say 85DegC and measure resistance again you can solve for B.

Here is my article on how to use a thermistor:

http://liudr.wordpress.com/2011/02/10/measure-temperature/

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