3 Wire

3 wire is used to describe a type of electrical connection for a measurement signal which has only three connections for the power supply and signal output, so that the common/negative connection of both are connected and are at the same potential voltage.

A typical example is a 1 to 5 volt output, where there is a separate supply positive, output positive and shared supply/output negative connection.

3 wire is also used to describe a resistive thermometer that is wired so that the error caused by the connecting wire on each side of the resistive thermometer is compensated. Only one side is connected and it is assumed that errors caused by the each wire are the same. therefore this method is less accurate that the 4 wire configuration.

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Connecting a 3 wire pressure transmitter

How is a 3 wire 4-20mA pressure transmitter connected electrically?

The 3 wire configuration is similar to the more common 2 wire configuration but the positive voltage supply is separated from the current loop:

Example of Sensor Connections:

Volts Input + (Supply positive)
Current Output + (Signal positive)
Volts Input (negative) / Current Output (Supply negative)

Measurement Signal Related Terms

More pages related to measurement signal technical terms.