Selection of instrument cables
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May I ask how many cores are required for the cables of control valves, transmitters, mass flow meters, thermal resistors, and thermocouples? 1*2*1.5, 1*3*1.5, 1*2*2.5, 1*2*2.5 – 4-core, 6-core. What are they used for? What is the maximum laying distance for cables?
For control valves, transmitters, and mass flow meters, 2*1.5 mm² cables are generally used; for thermocouples, 2*1.5 mm² compensation wires are typically chosen, while for thermal resistors, 1*3*1.5 mm² cables are used. 4-core and 6-core cables are usually used as main cables or as specialized cables for instruments such as mass flow meters. The transmission distance generally has little impact, as what is transmitted through the cables is a 4-20 mA current signal, rather than a voltage signal.
I agree with what was said above. Generally, flow meters that are not throttle elements use a four-wire or three-wire configuration. It is also necessary to use shielded cables; in some cases, explosion-proof hoses or armored cables may be required as well
Generally, there is no major issue with cable laying within 1000 meters; however, I think caution is needed when the distance exceeds 1000 meters~
Signals linked to DCS generally use computer cables. For those three-wire or four-wire instruments, you need to calculate the voltage drop to see if the voltage is appropriate. For the longest alarm cable, I have used one that is 800 meters long; I performed calculations at that time and found that the voltage remained within the range allowed by the instrument.
For control valve signal wires, 2*1.5 cables are generally used, while 5*2.5 cables are used for control lines; for mass flow meter signal wires, 2*1.5 cables are typically used, and 2*2.5 cables are used for power supply wires
1*2*1.5 is generally used for two-wire instruments; 1*3*1.5 is typically used for thermistor signal wires. 1*2*2.5 is usually employed for power supply wires or solenoid valve signal wires. A 1*2*2.5 configuration with 4 wires is mainly used for four-wire instruments such as electromagnetic flowmeters, while a 6-wire configuration is primarily used for mass flowmeters and can also be used for valve control – one set is used for control signal input, and the other two sets are used for switch signal feedback
Generally, signal cables up to 1000 meters are fine, but for power supply, the voltage drop needs to be considered! ! ! ! !
6-core cables are more commonly used in electric control valves, with 2 cores for power supply, 2 cores for input, and 2 cores for output. Cables generally need to be shielded when used to control or transmit electrical current signals.