The pressure transmitter wiring method is:

Two-wire system: The direct current power supply (DC 24V) supplies power to the converter on site through two wires, and at the same time these two wires are the transmission lines for the output signal (4-20mA). For DCS, this two-wire system is a passive signal.

Three-wire system: Two wires transmit signals, and the other one provides power. The three-wire system means that the positive pole of the power supply uses one wire, the positive pole of the signal uses one wire, and the negative pole of the power supply and the signal negative pole share the same wire. The power supply voltage is mostly DC 24V, and the output signal is DC4-20mA. For DCS, this three-wire system is an active signal.

Four-wire system: Two power cables and two signal cables are generally used for instruments with higher power, such as electromagnetic flowmeters. For DCS, this signal is an active signal.