4-Wire Rtd Connections - Data Translation TEMPpoint DT9871U User Manual

Chapter 4

4-Wire RTD Connections

The 4-wire configuration offers the best accuracy with long connection wires, compared to the
3- and 2-wire configurations. The 4-wire connection scheme eliminates errors due to lead wire
resistance (R
automatically cancelled as long as the sense wires are connected.
Figure 9
3-Wire RTD Connections
The 3-wire configuration eliminates one wire from the 4-wire RTD connection. Lead wire
resistance (R
drop is essentially equal and opposite to the voltage drop across +Sense.
Figure 10
46
) and thermal heating. Wire impedance of up to 100 Ω anywhere in the hookup is
L
shows a 4-wire RTD connection.
Return
– Sense
4
R R
L
Figure 9: 4-Wire RTD Connection
) errors in the return wire from –Sense may be introduced unless the voltage
L
shows a 3-wire RTD connection.
RTD Channel
μ
425 A
Current
+Sense
3 2 1
R R
L L L
RTD