Change a 2 wire RTD to a 3 or 4 wire

Thread Starter

Gibson486

Joined Jul 20, 2012
355
If I add my own resistors, could I theoretically turn a a two wire RTD into a 3 or 4 wire RTD? In the real world, it is probably not feasible to do this (just buy a 3 or 4 wire RTD?), so this question is purely academic.
 

Thread Starter

Gibson486

Joined Jul 20, 2012
355
Thanks! Maybe I am over thinking this. If this use of 4 wire and 3 wire only if you are making connections from beyond the pcb where it is located? If the RTD is on the PCB where the measurements are being converted, I am guessing that all these R values really become negligible?
 

Reloadron

Joined Jan 15, 2015
7,501
You would be guessing correctly. :)

The RTD itself is no more than a leg in a bridge. If the bridge is nice and local so to speak you will have 3 fixed resistors and the RTD all comprising the bridge circuit. There is no lead resistance to speak of or compensate for. However, if I have my 3 fixed resistors on a board but my RTD (the sensor) some distance away then in some cases the lead resistance comes into play. This is where 3 and 4 wire measurements become important. This is especially true with low resistance RTDs.

Ron
 
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