Hello

I am using PT100 RTD to monitor temperature in my product.

PT100 Sensors will have a lead resistance which will give rise to offset error..

This needs to be compensated.
Do PT100 sensor manufacturers provide this compensation in the cable or should I provide it by using a wheatstone bridge?

If bridge is to be use then how should i go about it?
pls help me...

Regards
Mayuri

 

the way this is typically handled is that if the wire voltage drop is likely to be an issue you use a 4 wire RTD instead of a 2 or 3 wire RTD.

A two wire RTD uses the same two wires for sensing and for injecting the fixed current that produces the voltage drop that is what is actually measured.

A three wire RTD has a third wire for sensing voltage that bypasses the voltage drop in half the loop.

A 4 wire RTD has a 4th wire so the sensing is connected directly to the RTD by two of the wires and the other two wires are the current injection so that there is no voltgae drop to worry about.

Many (possibly most) RTDs come standard as 4 wire and people just jumper the two wires together at each side of the RTD and run two wires back because the error generated is so minimal they don't care about it. this is solely about the field cabling costs and has nothing to so with the sensor itself.

--
Bob
http://ilbob.blogspot.com/

 

The leadwire compensation is done by the device that the RTD connects to, not by the RTD or its interconnecting wires.

3 wire RTD connections are the most common because there is lead wire compensation with the assumption that the lead wire is the same gauge and length for all three legs - good enough, as they say.

If you've designed your own device that takes an RTD input, then you might want to look up Liptak's "Instrument Engineers Handbook, Vol 1 Process Measurement and Analysis" which shows measuring circuits for 2, 3 and 4 RTDs (page 651, 4th edition).