Four-wire to two-wire conversion
Thread Content
Dear experts, I originally had a Coriolis flow meter with a four-wire connection. Now, the warehouse only has flow meters that operate at 24VDC – can they be installed? How to install it? Can a four-wire signal line also be used as a power line? Can I just connect it directly to the signal line?
No, because DCS’s AI cards come in active and passive versions
Are the pipe diameters and flanges of the two flow meters in Cologne the same? It would be easy if it were the same! ! It’s just a matter of whether it fits or not; as long as it can be installed, there’s no problem at all, haha
The 220V power cable does not need to be connected; for the 4–20mA signal cable, a 24V power isolation device should be added, and it can then be connected directly to the existing PLC system
The four-wire system is different from the two-wire system; I have never encountered the latter in practice. After all, four-wire systems are basically powered by 220VAC.
All that’s needed for the cabinet is a connector card, the same AO connector card used in pressure transmitters; two of the four wires are utilized, and the wiring is done inside the cabinet
The difference between four-wire and two-wire systems lies in whether the AI cards in DCS are active or passive; as long as you use AI cards that are powered actively, there will be no problems. Moreover, today’s two-wire instruments are also powered by safety barriers, so as long as the instruments are installed properly on-site, everything will be fine.
For this issue, as long as you change the signal type of the original control cabinet to active, you can connect it directly using the existing signal wires
The instrument uses a four-wire system and is powered externally; it doesn’t require power from a circuit board. Just send the output signal to the circuit board, and that’s it. . . What’s there to worry about, dig?
"Can a four-wire signal line be used as a power supply? Can it be connected directly? " Answer: No. If you apply power to the current signal line of a four-wire instrument, that is considered incorrect wiring, and it will damage the instrument.
Who told you that all four-wire systems are powered by 220VAC? Two-wire, three-wire, and four-wire systems are applicable to instruments powered by direct current, and they have little to do with those powered by alternating current.