Can multiple 4-20mA wires on site be combined into one multi-core wire?
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This post was last edited by Syklon on 2017-3-11 21:54 with a request for help. . For example, if there are 5 signal points at a site, all transmitting 4-20mA signals to the DCS system from within one cabinet, that would result in 10 wires. Could we purchase a 10-core shielded cable for this purpose? Do we still have to use 5 2-core shielded wires? Multi-core wires can save a lot of costs.
This post was last edited by Syklon on 2017-3-11 23:56. Thank you; how should we handle the power supplies that are isolated from each other? The power supply for our on-site sensors (flow meters, weighing modules, etc.) comes from DC24V generated by the respective instruments; the power supply for these instruments itself is provided by the company’s unified 220V supply. The sensor signals are first sent to the corresponding instruments, which then convert them into 4-20mA signals that are sent to the DCS system. Following your advice, I plan to buy multi-core twisted pair cable so that the total cost can be lower. On this basis, what needs to be done with the power sources that are isolated from each other?
The same signal can be transmitted using one multi-pair cable.
We use 32-core cables for the connection from the on-site terminal box to the DCS
It is fine to use one multi-core cable for the signal and one cable for the power supply
Leave 1-2 spares; it’s most reliable to buy cables of specification 6(7)×2×1.5(1.0)mm2 with a main cable and a counter cable
In all these years of working in this field, I’ve never encountered any problems caused by poor shielding. This includes transmitting voltage signals and thermocouple signals over distances of over 200 meters; for instance, thermocouple wires are not shielded, and no one has proven anything regarding single-point grounding, although multi-point grounding is indeed used in some cases. As for current signals, that’s even easier. Even when interference issues arise, they are not resolved by checking the shielding; they are problems other than those related to shielding. So I think calling it a block might be an overstatement. Of course, it should be done in accordance with the standards; try to follow the standards as much as possible.
This is feasible~ It’s a multi-strand, two-core twisted shielded cable, with both the overall shield and the individual shields needing to be grounded~
You can buy that 10-core shielded cable with 5 pairs of twisted pairs