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

Wiring Signals
RTD Channel
μ
Return 425 A
Current
– Sense +Sense
4 3 2 1
R R
L L
*R is lead wire resistance.
RTD
L
Figure 10: 3-Wire RTD Connection

2-Wire RTD Connections

The 2-wire configuration is the least accurate of the RTD wiring configurations because the
lead wire resistance (R ) and its variation with temperature contribute significant
L
measurement errors, particularly if the lead wire is long. If you decide to use the 2-wire
connection scheme, ensure that you use short lead wire connections.
For example, if the lead resistance is 0.5 Ω in each wire, the lead resistance adds a 1 Ω of error
to the resistance measurement. Using a 100 Ω RTD (Pt100) with a 0.00385/°C European curve
coefficient, the resistance represents an initial error of 1 Ω /(0.385Ω /°C) or 2.6°C. Since the
lead wire resistance changes with ambient temperature, additional errors are also introduced
in the measurement.
Figure 11 shows a 2-wire RTD connection.
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