What is the difference between a Two-Wire and a Three-Wire Transmitter?
The three-wire transmitter is a blend of the four-wire and the two wire versions. The four-wire transmitter has two wires for power and two wires for the output signal. The power for a four-wire transmitter can be either AC or DC and the output signal can be either voltage or current. The two-wire transmitter has two wires for both power and the output signal. A two-wire transmitter is always DC powered and the output can only be a current signal, typically 4-20mA. The three-wire transmitter uses two wires for power and the third wire is used for the output signal (+) positive terminal. The power (-) negative terminal is used as a common reference for power and the signal (-) negative reference. This allows the best of both transmitter features to be utilized. There is one less wire required than a four-wire transmitter and powered outputs are provided for both 4-20mA signals and 0-10V signals. These transmitters can be lower in cost than four-wire transmitters because they are DC powe
