Autosport Labs

http://www.autosportlabs.net/RaceCaptur ... s#GM-Style

The published curve for the Wells SU109 will only give me temperatures up to 212F/100C. What is being used for temperatures over 212F? Like coolant, or oil. Who has a car that reads coolant temp that stops at boiling? That is why we run a pressurized system after all.

Is there as better sensor to use for this then ? It seems like the meat of this sensors range covers temperatures that are from 23-178F. After that voltage differential drops off.

So, what do we use for oil temp, or coolant temp in a car that is actually racing because 212 is not even close to high enough.

Thanks,
Phil

These are extremely common sensors for measuring coolant temperature, but many of the resistance charts out there only go to approximately 210 degrees F.

I'm certain you can get a usable range to 250 degreesF or so, but what probably needs to be done is hand measure one of these sensors into this range and go from there.

The alternative is to extend the curve into this range and extrapolate the resistance measurement, which may be an acceptable estimation.

Would you like to take these measurements and report back?

Well there are published tables for sensors that look strangely identical but using a 2.2k pullup will make the high temp voltages dwindle too low. ~0.11V.

I could reduce the pull up to 1k making a 100k sensor ( at -40C) have an output voltage of 4.95..

Here are the things I don't know:

What is the A/D precision ?
What is the Impedance of the A/D? ( If it were 10k that would drop my output to 4.5v )
What is the max input voltage of the A/D?


The right answer is likely to drop the pullup resistor value and sample deeper into the range. The span would widen by 0.3 volts to 0.5 ( from 212-300 ) instead of only 0.2v using the 2.2k.

Since I don't really care what happens at 32F anyway a pull up of 150ohm could provide a 1.45v range ( from 212-300) , but I'm not sure about the current bleed off through the internal A/D circuit if the sensor being measured is removed, and the ground path becomes the A/D.

Thoughts?

Phil

Actually, I re-read the post and saw you mentioned oil temperature.

In that case, I would recommend the AEM-style unit listed below the GM unit (we've been searching for the generic oem equivalent of this sensor). Note, the resistance curve extends into the 300 degree range.

If you find out what OEM equivalent this is, please let us know!