Editing Resistance thermometer (section)

===Three-wire configuration===
[[File:RTD 3Wire.svg|Three-wire RTD Wheatstone bridge]]

In order to minimize the effects of the lead resistances, a three-wire configuration can be used. The suggested setting for the configuration shown, is with R1 = R2, and R3 around the middle of the range of the RTD. Looking at the [[Wheatstone bridge]] circuit shown, the voltage drop on the lower left hand side is V_rtd + V_lead, and on the lower righthand side is V_R3 + V_lead, therefore the bridge voltage (V_b) is the difference, V_rtd &minus; V_R3. The voltage drop due to the lead resistance has been cancelled out. This always applies if R1=R2, and R1, R2 >> RTD, R3. R1 and R2 can serve the use of limiting the current through the RTD, for example for a Pt100, limiting to 1&nbsp;mA, and 5&nbsp;V, would suggest a limiting resistance of approximately R1 = R2 = 5/0.001 = 5,000 Ohms.