Measurement Computing WLS-TEMP - Manual (Page 16)

WLS-TEMP Specifications
16
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 6.
Figure 6. Three-wire RTD or thermistor sensor measurement configuration
When you select a three-wire sensor configuration with InstaCal, the WLS-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.
For accurate three wire compensation, the individual lead resistances connected to the ±I# pins must be of equal
resistance value.
Four-wire configuration
With a four-wire configuration, connect two sets of sense/excitation wires at each end of the RTD or thermistor
sensor. This configuration completely compensates for any lead-wire resistance and temperature change in lead-
wire resistance.
Connect your sensor with a four-wire configuration when your application requires very high accuracy
measurements.
You can configure the WLS-TEMP with either a single sensor per channel or two sensors per channel pair.
Four-wire, single-sensor
A four-wire measurement configuration is shown in Figure 7. The diagram on the left shows the sensor
connected to the first channel in the channel pair. The diagram on the right shows the sensor connected to the
second channel in the channel pair. The # indicates the channel number. Do not make connections to pin
marked "NC".
Figure 7. Four-wire, single RTD or thermistor sensor measurement configuration