For a cut-off valve, can the switch feedback be achieved using only three wires?
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Typically, a control valve has two sets of four wires for feedback on its open and closed states; one set indicates the valve is open and the other indicates it is closed, with both sets connected to digital input channels. In principle, it seems that three wires would be sufficient, with one wire serving as a common line – so why waste an additional wire? I asked my boss, and he said no; it seems he doesn’t know the reason either. Is this acceptable? What do you fellow professionals think?
I guess it’s not possible, because after market hours there are two separate areas, meaning there’s a safety barrier in place to separate them. That’s what I think; I’m not sure if that’s correct
Take it apart and take a look – is that wire indeed shared?
You mean the switch reply; three wires will work. As for the solenoid valve, it originally has three wires.
There are generally two types of valve position feedback switches: 1. The open and closed feedback functions are combined into one, with just one wiring terminal, allowing the use of a 3-core wire. This is all a result of the design institute’s design habits; the use of 4-core wires was done without proper consideration. 2. The on and off reply functions are controlled by two separate switches, each with its own wiring terminal; as a result, only 2 two-core wires can be used.
Thank you, I was talking about the two paths splitting apart. It seems like I understand now, hehe
Thank you all. I think a three-wire system should work fine; perhaps separate wires are used for reasons such as clearer logic in the design and simpler wiring. I’ll give it a try in practice later.
Three wires: connect the two common wires together, and the built-in switch can be connected to one on/off setting or two on/off settings; either is acceptable. Simple
My previous workplace used three wires for all signals: one common wire that was green for on and yellow for off, which was very clear and easy to remember
If it is to connect to a PLC or DCS, there are usually common terminals, so three wires are sufficient. If it is to be connected directly to the secondary circuit for control, such as in an electrical control box, four wires are required; otherwise, voltage interference will occur
On the PLC side, it’s still three wires. . . . :L:L:L