USB-TEMP User's Guide
Sensor Connections
3-5
Two-wire, single-sensor
A two-wire single-sensor measurement configuration is shown in Figure 3-3.
I#
+
NC
C#H
C#L
4W#
#
IC#
#
C#H
C#L
GND
I#
-
Figure 3-3. Two-wire, single RTD or thermistor sensor measurement configuration
When you select a two-wire single sensor configuration with
Insta
Cal, connections to C#H and C#L are
made internally.
Two-wire, two sensor
A two-wire, two-sensor measurement configuration is shown in Figure 3-4.
I#
+
NC
C#H
C#L
4W
#
#
IC#
#
C#H
C#L
GN
D
I#
-
Figure 3-4. Two-wire, two RTD or thermistor sensors measurement configuration
When you select a two-wire, two sensor configuration with
Insta
Cal, connections to C#H (first sensor)
and C#H/C#L (second sensor) are made internally.
When configured for two-wire mode, both sensors must be connected to obtain proper measurements.
Three-wire configuration
A three-wire configuration compensates for lead-wire resistance by using a single voltage sense
connection. With a three-wire configuration, you can connect only one sensor per channel pair. A
three-wire measurement configuration is shown in Figure 3-5.
I#
+
NC
C#
H
C#
L
4W
#
#
IC
#
#
C#
H
C#
L
GN
D
I#
-
Figure 3-5. Three-wire RTD or thermistor sensor measurement configuration
When you select a three-wire sensor configuration with
Insta
Cal, the USB-TEMP measures the lead
resistance on the first channel (C#H/C#L) and measures the sensor itself using the second channel
(C#H/C#L). This configuration compensates for any lead-wire resistance and temperature change in lead-
wire resistance. Connections to C#H for the first channel and C#H/C#L of the second channel are made
internally.
