thermistor help

Hello,

I am developing a device which opens and closes a cover over a raditor to control engine coolant temperature. The device works with a K Type thermocouple. The drivers computer can also read the temperature with a thermistor sensor. A link to the data sheet is below, but it has limited value as it is incomplete.

(http://www.aimsportline.com/download/doc/eng/sensors/Datasheet_ThermoresistorM10_105_eng.pdf).

I also attached a pic of the only useful page which has the pin out.

Is the code different for NTC and PTC thermistors? I have only been able to find sample code for the NTC type. I have been able to read the temperature but it fluctuates too much and does not go up and down with heat. Also I was able to measure about 110 ohms across A0 & GND. Also this vaule does not change with heat. It has three active wires, VCC, GND, Analog Signal. The 4th wire is GND also but not used. The sensor works when hooked up to the drivers computer(mounted on the steering wheel).

Any help would be much appreciated.

Thanks,

David

Is the code different for NTC and PTC thermistors?

Of course it is. You will need an appropriate method of estimating the temperature from the measured resistance.

The link to the data sheet does not work.

This link? No real information there.

Yes, code for NTC or PTC is different. Most thermistors are NTC.

Measure the resistance of the (disconnected) sensor (pin 1 and 4) at room temp (~25C). Then see if resistance increases (PTC) or decreases (NTC) if you warm it with your hands (or a hair drier). Leo..

A simple way to calibrate your sensor is to measure the resistance at several temperatures of the range of interest, and fit a curve to the data.

That is how NTC thermistors are calibrated, and the curve most often used is the Steinhart-Hart approximation. Here is an on line calculator for that.

This link? No real information there.

Not even that it is a PTC sensor.

Use a DS1820 sensor , easier and accurate

Hey Fellas thanks for the response.

WAWA yes that is the link. Agreed not much to go on. The reading jumps around when I disconnect and reconnect the probe, poor consistancy. When I hold the probes steady the reading jumps around. I have tried two different instruments and both show different readings. I just checked them both with a 10K resistor and they both read near 10K steady. Not sure what to make of it.

Hammy the DS1820 was the 1st sensor I tried. Agreed it was easy. Aim Sport is using the sensor I'm asking about with their driving console. I am attempting to hack into to it to use the signal. This sensor is on everyone's kart so it would be great to be able to use it. If I can't hack in to it then I will have to drill and tap into the hoes fitting to add another sensor, which does the same thing.

Jremington I'm not sure what you meant. Do think that the sensor is not a PTC sensor? If not what do you think that it is?

Do think that the sensor is not a PTC sensor?

There is nothing in the data sheet stating the type of sensor.

Why do you think it might be PTC?

jremington, The data sheet describes it as a themsitor. I did some research and learned that they are NTC or PTC. I thought that when I measured the resistance it increased when heated. But I have not been able to reproduce this. Every time I try to measure it I get different results. I’m stumped. Also when I hooked it up to an Arduino with many sample code sets it didn’t work. I am hoping to find someone who can help me figure out what this sensor is and then get a reading with an Arduino. Then hopefully split the signal and run it into my board to control a devive.

You must be able to make repeatable and reasonably accurate measurements of the resistance versus temperature before you can make use of the sensor.