Electronic temperature measurements

[Minerva]

Which would be the preferred way to measure the temperature of egress oil from a D19 compressor? A well has been affitted already. The temp never exceeds 200 degrees Centigrade.

The output is tracked and recorded with conventional instrumentation so there is a lot of flexibility in the transducer type. The screw has been troublesome so fast response times are preferred. -M-

 

[miniMUNCH]

How accurate do need the measurment to be and how much are you willing to spend?

Accuracy goes like this: Thermistor or high quality diode (+or- 0.1 deg. C) > RTD or low quality diode (+or- 0.2-0.5 deg. C) > thermocouple (+or- 1-2 deg. C) -- of course you'll need to calibrate or least check the calibration of whatever you end up going with. But you can do a 2 point calibration easy eough in an ice bath and boiling water.

I don't know of any thermistors off hand that are rated to 200 C (but there might be some that are). RTD can get pretty expensive and thermocouples are cheapest by far.

All of these devices themselves have fast response time...the total system response to a fluid temperature change will be determined by heat transfer to/from the well.

I don't know what a D19 compressor is...so is this for work or play? If work, where do you work?

Edit: I used to do process system and control engineering for living. I'm in grad school now.

 

[Cattlegod]

Thermocouple FTW. we use them in the auto industry to measure transmission temperatures, etc. just hook one up to a multimeter and bam, you have the temp.

edit - and for response times - it doesn't matter, it is generally up to the sample rate you use in the software acquisition package to get the resolution you need.

 

[Minerva]

I'm seeing more and more feedback (uh huh what a pun!) that says use thermocouple.

Does not have to be NIST accurate but faithful and track quickly. They'll use this information to find out what's going on before they do a teardown which may be avoided actually. They don't want to spend the money to replace the entire unit with an up to date one but will have to face the fact that it's coming.

It's a water-water chilling machine (1150 ton) to process sea water fit for cetaceans. -M-

 

[duragezic]

I'd guess thermocouple. I don't know crap about the subject but at work I've been doing a little bit of testing on this oil product, and the temperature is measured with a thermocouple!

 

[miniMUNCH]

So do you have a particular budget for the temperature device. A TC will just cost about a dollar per foot of wire from the measurement location to the transmitter. A good RTD is about $100-150 dollars.

I'd say, if you don't want any problems with the measurement use an RTD as long as it is within budget.

What process indicator are you using?

 

[miniMUNCH]