Measurement-computing USB-5203 Manuel d'utilisateur télécharger pdf (Page 14)

USB-5203 User's Guide Sensor Connections

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 USB-5203 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.

Three-wire compensation

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. Examples of a four-wire single-sensor measurement configuration are shown in Figure 7 and

Figure 8.

You can configure the USB-5203 with either a single-sensor-per-channel, or a two-sensor–per-channel pair.

Four-wire, single-sensor

A four-wire, single-sensor connected to the first channel of a channel pair is shown in Figure 7.

Figure 7. Four-wire, single RTD or thermistor sensor measurement configuration

A four-wire, single-sensor connected to the second channel of a channel pair is shown in Figure 8.

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Measurement-computing USB-5203 Manuel d'utilisateur Page 14