Wiring the control line midway

It will have an impact. Intermediary wiring of control lines, especially over a distance as long as 260 meters, can easily lead to contact resistance and signal attenuation at the connection points, and it may also introduce interference. The signals from pressure transmitters are usually weak (such as 4-20mA), and these factors can lead to unstable signals, fluctuating readings, or increased errors. If it is necessary to make the connection, be sure to use a waterproof junction box; tighten the wire ends and solder them, ensure proper insulation and shielding, in order to minimize any impact. But in the long run, it’s more reliable to replace the entire wire with a new one. .

Would it be better to add an inlet and outlet isolation barrier at the break point?

Adding a barrier can indeed improve this problem, but attention should be paid to its usage. The main function of the isolation barrier is to block interference and protect equipment; it cannot repair the signal attenuation caused by the broken wire itself. If you connect the wires at the break point and then install a shield on the side closest to the pressure transmitter (rather than at the break point), it will serve two purposes: 1. **Isolating interference**: It can effectively suppress external electromagnetic interference that may arise from poor connections at the joints. 2. **Signal reshaping**: For digital signals or the HART protocol, a good isolation barrier can reshape and regenerate the signal, thereby improving its quality. **Therefore, the correct way to do it is: **1. At the break point, use professional wiring terminals or welding to connect the wires** firmly**, and ensure proper waterproofing and insulation. 2. Install a one-input-one-output signal isolation barrier at the controller side (such as the input side of the PLC/DCS cabinet) or at the pressure transmitter side. **Special reminder: **Do not install the isolation barrier directly at the field disconnect points exposed to wind and sunlight; it should be installed inside an instrument cabinet or protection box. **To sum up: **First ensure a reliable physical connection, then use isolation barriers to improve signal quality.** This is an effective remedy, much better than simply connecting the wires. If extremely high measurement accuracy is required, replacing the entire wire remains the best option. .

What specifications should this isolation barrier use? Does it need to be designed first?

This post was last edited by DLP Instrument Liu on 2025-11-17 08:17. What impact can a distance of around 200 meters have? Just add a junction box and that’s it; it’s not that costly. It’s normal to add a junction box between the field panel and the control room.

For a distance of 260 meters, it’s sufficient to ensure that the joints are waterproof. In many designs, there are wiring boxes and terminal cabinets – aren’t those used for intermediate connections? It’s not that delicate!

The isolation barrier requires power, so power cables need to be led to it. It’s simpler to just replace it with another one.