Understanding 3 Wire RTD Theory: Operation and Measurement Error

[jingles]

I would like to confirm the operation of a 3 wire RTD.
The 3rd wire is a high impedence voltage measuring lead only and does not conduct. Call it "C"

The other 2 leads we will call A and B and do conduct. The resistance of these two leads introduce a measurement error.

My assumption is that C measures the loop voltage before the resistance of one of the leads then measures the loop with both lead resistances.

The electronics then do a calculation which should look like this

(A+B+RTD)-(A or B+RTD)=Resistance of A or B

Therefore (A or B+RTD)-(A or B)= True temperature of RTD

Seems simple but I could not find the data to confirm this anywhere on the net

 

[anorlunda]

RTDs come in 2, 3 and 4 wire configurations. This article explains and shows wiring diagrams.

https://en.wikipedia.org/wiki/Resistance_thermometer#Wiring_configurations