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Author Topic: Measuring temperature with a thermistor.  (Read 1458 times)

deejayry

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Measuring temperature with a thermistor.
« on: September 13, 2006, 12:19:40 PM »

Hey guys, its been a while since i've been here, since my desktop died, modding has been given a very low priority so i've not really had much to report here.

in February i bought a data logger for my racing mini i intend to use it to measure vital temperatures and pressures around the engine.

The pressure bit is easy, most of the sensors available have the 0-5v output i need to feed in to the data logger.

to measure the temparature i'm going to use a 2.5k @ 25c thermistor. i've managd to build a farly basic circuit to do the job but its not very stable and is likely to be affected by the noisy electrics of the car, so i need to find a better solution. I've got part of it designed but i'm a bit unsure of the schematics.

I'm going to use a constant current source, feed its output through the thermistor and then amplify the signal to fit in the 0-5v range for the data logger.

I've got the schematic for the constant current source but i could do with some help with the amplifier

I'm using an op amp for the constant current source, and i'm 99% sure that i need to use one or more op amps to make the amplifier circuit. I've chosen to use the LM324 op amp because it can be run from a single sided power source, whereas most others require a +v -v supply.

Here's a pic of the constant current source.


I've not yet chosen the current to feed out of the constant current source, i intend to match it with the input requirements of the amplifier circuit.

Any ideas guys? i know its not very computer based but you are the only people i know that might be able to help. i know that there are some people with good brains hanging around here.

Thanks.
« Last Edit: September 13, 2006, 02:04:16 PM by deejayry »
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