Number of cable cores
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Many instruments require signals to be sent back to the control room, which necessitates the use of cables. So, how many cores should such cables generally have? Are thermal resistors, thermocouples, and electromagnetic flowmeters three-core? What about differential pressure transmitters and pressure transmitters?
Thermal resistors are three-wire, electromagnetic flowmeters are four-wire, and all others are two-wire.
Resistors use three wires, thermocouples use two wires, and transmitters use two wires; the wire gauge is usually 2*1.5 or 3*1.5.
For thermal resistors, a transmitter unit is usually added on-site, resulting in a two-wire connection; two wires are commonly used for pressure and temperature measurements on site.
For thermal resistors, a three-wire type should be chosen; for thermocouples, a two-wire type is appropriate. Transmitters also require two wires: one for power supply, which must have at least two wires, and the other for signals, which also needs at least two wires. Although differential pressure transmitters and pressure transmitters operate on different principles, a two-wire setup is sufficient for them as well.
Thermal resistor: three-wire with shielding. Thermocouple: two-wire compensation wire with shielding. Electromagnetic flowmeter: two wires for the signal with shielding, two wires for power without shielding. Transmitter: two-wire with shielding. Choose 1.0 for short distances, 1.5 for longer distances, and 2.5 or more for even longer distances