Liquid level sensors

In the past, I sometimes used a simple Kriwan INT69 to control a liquid level. Connected two stainless steel bolts on the thermistor entrance and it worked fine.

What's also interesting literature is that you can measure vacuum perfect with a thermistor. They heat a thermistor and the more air there is around the thermistor, the more it can cool. So in a perfect vacuum, there are no air particles anymore which can cool the thermistor and you will have maximum heat. This is measured by some sort of amplified Wheatstone bridge.

They cal it Pirani thermistor gauges.

http://www.bgu.ac.il/~phys/COURSES/E...easurement.doc

This is als the working principle of some anemometers (heated wire).

Yes Peter, I have a vacuum gauge working on a thermister, made by CPS and cost around 130GBP.

It's a lot lighter to carry around and less liable to pressure damage.

Brian, do you know if they use for this a single thermistor or a Pirani (2 thermistors)

It's because my son is building something and some advice can allways be usefull.

I think it is a single but I will check and come back to you.

Try this link, it shows the kit I'm using...
http://www.cpsproducts.com/vacrometer.htm