Go Down

Topic: PT1000 RTD help please (Read 5 times) previous topic - next topic

gg123

Thanks for all of those.....I have just one sensor so far for development, I'd like to use alternatives but all the immersion type sensors on the market for insertion into hot water tanks seem to be RTDs. Range needed is only from 0 to +90 deg C, and +/- 1 deg accuracy would be fine.

I'll post whatever I end up with here...

EmilyJane

What kind of material does the sensor have to be made of to immerse in hot water? Thermocouples come in stainless steel and Inconel for example.

A lot of the issues regarding signal conditioning RTDs go away with PT1000s because of the higher resistance. For your application, I'd be tempted to use a precision resistor with a good temperature coefficient of, say 3K3, in series with the sensor and monitor the sensor voltage with the Arduino. Then, I'd do a three point calibration with a good thermometer, say ice slurry, boiling water, and something in the middle and call that good.

Definitely let us know how it goes.

gg123

Sorry, I didn't describe it well - they are not actually immersed themselves, but slide into a close fitting immersion sleeve, like this

http://www.alternativeenergystore.co.uk/item/item/102201/1/0/100mm-Stainless-Steel-Immersion-Sleeve.htm

which are screwed into fittings in the water tank and the solar collector.

Thanks for the advice on the resistor, I'll certainly try that and report back when it's all together.

retrolefty

#8
Sep 15, 2011, 01:09 am Last Edit: Sep 15, 2011, 01:10 am by retrolefty Reason: 1

Sorry, I didn't describe it well - they are not actually immersed themselves, but slide into a close fitting immersion sleeve, like this

http://www.alternativeenergystore.co.uk/item/item/102201/1/0/100mm-Stainless-Steel-Immersion-Sleeve.htm

which are screwed into fittings in the water tank and the solar collector.

Thanks for the advice on the resistor, I'll certainly try that and report back when it's all together.


Those are called 'thermowells' in the process control industry. They allow one to remove/test/replace the sensor without having to drain the tank. However one has to insure the sensor tip 'bottoms out' inside the well or you can end up with slow responding or even inaccurate measurement values.

http://www.temperatures.com/twells.html

Lefty

gg123

Thanks Lefty - is some kind of thermal grease used to ensure good readings? I was toying with the idea of using a sensor easier (to me at least) to hook up rather than a PT1000, and packing it in with something, as a plan B really if else fails.


Go Up