What to do if a 2-wire control valve has a signal but no power supply?
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I purchased 2 new control valves, of the 2-wire 24V 4-20mA type. Since I don’t have a DCS, I bought 2 Fuji PXR9 temperature controllers to use for controlling them. However, when they arrived, it turned out that the 4-20mA signals generated by those temperature controllers were passive. What should I do? Is it possible to connect another 24V power supply to the signal of the control valve to power it?
This post was last edited by tiger2010 on 2017-10-26 at 16:11. Should it be strung together? :Oh, it hasn’t been done this way before; you can try it out by simply connecting the current setting into the circuit. At worst, the fuse will burn out
Basically, all digital displays and controllers come with a separate 24V output. Carefully read the instructions: connect one wire to the 24V+ terminal of the digital display, and the other wire to the 4-20mA+ terminal of the digital display. Then short-circuit the 24V- and 4-20mA- terminals on the digital display. If there is truly no 24V terminal on the CNC controller, then find a switching power supply and connect it in the same way.
This post was last edited by jujiangliu on 2017-10-26 at 16:21. Is the 4-20mA output of the temperature controller passive? It can be connected to a 24V DC power supply.
Connect a 24V DC in series.
Is it confirmed that the temperature controller output is a passive signal? It’s very rare usually. If not, just connect a 24VDC between them.
You can handle active temperature control output, but I guess your valve isn’t controllable either! Serial control valves are generally regulated by PID in DCS systems
It won’t operate either if there is only a signal but no power control valve. As I understand it, instruments with a 2-wire system are considered active, meaning they have their own power source and do not require external power supply； Meters with 4 wires are referred to as passive; they have no internal power source and require external power supply, right?
Well, I’ll give it a try tomorrow. The Fuji PXR9 really doesn’t have a 24V supply; its operating voltage is 220V