Selection of thermoresistive cable
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I have a question: Each terminal junction box is connected to 8 three-wire thermal resistance meters, and these are connected to the DCS system via 8*3*1.5 multi-core computer cables. However, the cables purchased were of the 8*2*1.5 type instead. Can I add another cable of the same specification, namely 8*1.5, to make up for it? Does it affect the measurement accuracy? If possible, where should the 2-core and single-core wires be connected to the A, B, and C phases of the resistor? (In thermal resistors, BC are red wires, and A is a white wire)?) Help needed
If the shielding is done properly, there should be no significant impact; the key is to prevent electromagnetic interference
It’s possible; it can be connected to the thermistor in any way, but it needs to be connected properly on the display instrument.
Under normal circumstances, the three signal wires of a thermal resistor should be enclosed within the same shielding layer, so that they are exposed to the same external influences. However, since the cable ordered is already an 8*2*1.5 type cable, we can connect them for now and see how it works; under normal conditions, it should yield good results.
It is possible to add an 8*1.5 cable of the same specification; in thermistors, B and C are red wires connected in a 2-wire setup, while A is a white wire connected as a single wire. To be more certain, it’s necessary to measure the resistance between points B and C; if the resistance is around 0.1 ohms, then it means they originate from the same point.
If no purchase is made, it is recommended to order a few more cores for backup in future purchases. Make sure the cable lengths are as similar as possible when laying them
Would it be better to use cables with more cores for addressing this issue? If one cable is connected to 5 resistors, that would require a 15-core cable; the other 3 resistors would then require a 9-core cable. Is that a better approach?
If the cables are from the same manufacturer and have exactly the same core material, it can be used this way; the length of this individual cable should be the same as that of the previous ones. Just ensure that the wiring at the thermal resistor is consistent with that at the DCS; I recommend using red for the individual wire.
When we encounter this situation, we usually first use up the existing 8 sets; if that’s not enough, then we lay 3*3*1.5 as needed