National Instruments Module SCXI-1503 - Manual (Page 18)

Chapter 2 Connecting Signals
© National Instruments Corporation 2-5 SCXI-1503 User Manual
3-Wire Resistive Sensor Configuration
If you are using a 3-wire resistive sensor, you can reduce the error voltage
by one-half over the 2-wire measurement by connecting the device as
shown in Figure 2-3. In this configuration, very little current flows through
R
L3
and therefore R
L2
is the only lead resistance that introduces an error into
the measurement. The resulting measurement error is:
Figure 2-3. 3-Wire Resistive Sensor Configuration
VE R
L2
I
EX
=
+
–
SCXI-1503
Channel X
IEX+
AI+
AI–
IEX–
SCXI-1306 External Sensor
ON
CH X
I = 100 µA
R
L2
R
L1
R
L3
R
T