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How to select the temp. sensor. Is there any selection procedure?

1. suppose if i am going for RTD. how can i select my process system require pt100 or cu or ni.

2. suppose if i am selecting T/C. there are many types. which one i have to select.

3. please keep me the detailed information for temp. element selection.

4. and also need the selection of thermowell & the materials.

It depends on a lot of different factors:
Cost,
how hot is the process,
how accurate does it need to be,
are you going to use field transmitters
or wire directly to your control system,
is it permanent or just a temporary measurement.

I usually spec RTDs for anything less than 200C because I think they are more accurate and the wiring is more reliable. For small skid work type "K" thermocouples are cheap and will fit in tight spaces.

If you have 1 or 2 really hot measurements you might decide to use thermocouples right across the board so you only have one type of input card. 100 Ohm Pt 0.0385 is the most common range of RTD for process, 10 Ohm copper is common for measuring motor winding temperature but I have never seen it used elsewhere.

With thermocouples you also have to think about the interconnection cables, it's becoming harder to buy multi-pair cables. Type "K" thermocouples are probably cheaper to install than any other type

These are just a few ideas.

All the points that you have asked are the issues that are related to design criteria, for example for the material of the thermowell, fluid is important, or the type of the RTD depends on the range of the temperature you want to measure. There are some standards that you can be referenced for.

Hope this helps you.

I suggest you talk to a local controls company such as a branch of Rockwell or ABB, or their distributor. They will ask you all about the fluids you want to measure, and then temperature ranges, media details, speeds of response, mounting types, environmental protection, cabling distances and more. They will then help you draw up a specification for each measurement (and control) point, from which they will identify suitable hardware and quote you.

Alan Balcombe

JMS is a manufacturer of RTDs, Thermocouples and Thermowells. You've asked some great questions but the answers are pretty long for an internet forum.

Give us a call and inquire about temperature school and the fundamentals DVD. That literature should provide you with answers to all of the questions you've asked and more.

If you have specific questions about a particular application our folks will be glad to give you a manufacturer's perspective.

www.jms-se.com

Best regards,
Mitch

May I ask you to give us an email to be able to contact and requesting the DVD?

Vahid

Go to Omega.com and they will send you "FREE" all the information you can use in Hard back and softback books.