The transmitter needs external power supply during use, and the wiring of the transmitter mainly includes two wires, three wires, and four wires. In today’s article, we will take you to understand the similarities and differences between the power supply of different wiring forms of transmitters. The two-wire power supply of the transmitter is 24V.DC The wiring diagram of the two-wire system of the transmitter is as follows, its power supply is 24V.DC, the output signal is 4-20mA.DC, the load resistance is 250Ω, the negative potential of the 24V power supply is the lowest, it is the signal common line, and the FSK keying signal of the HART protocol can also be loaded on the 4-20mA.DC signal for the intelligent transmitter.

Most of the three-wire power supply of the transmitter is 24V.DC The three-wire wiring diagram of the transmitter is shown in the figure below, the so-called three-wire system is that the positive end of the power supply is used with a wire, the positive end of the signal output is used with a wire, and the negative end of the power supply and the negative end of the signal share a wire. Most of its power supply is 24V.DC, the output signal is 4-20mA.DC, the load resistance is 250Ω or 0-10mA.DC, and the load resistance is 0-1.5KΩ; Some also have mA and mV signals, but the load resistance or input resistance varies depending on the output circuit form.

Most of the four-wire power supply of the transmitter is 220V.AC, and some power supply is 24V.DC The wiring diagram of the four-wire system of the transmitter is shown in the figure below, and most of its power supply is 220V.AC, and some power supply is 24V.DC. The output signal is 4-20mA.DC with a load resistance of 250Ω, or 0-10mA.DC with a load resistance of 0-1.5KΩ; Some also have mA and mV signals, but the load resistance or input resistance varies depending on the output circuit form. When the on-site power is large and the accuracy is required to be high, the four-wire transmitter is generally selected.

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