Kuhnke 16 Point 4-20mA Output

[cekann 0]

I have a wood belt sanding machine that has independant "shoes" to apply varied pressure to the work. Originally this was controlled by a Kuhnke 657 PLC. As far as I can get any information, the output card is 16points, 4-20mA. Each output then controls another electronic device (SCR?) the switches a solenoid at a proportional ammount (determined by the 4-20mA). The solenoid applies pressure to the sanding shoe. I have had to replace the Kuhnke with an AB ML1400. However AB does not offer a comparable 16 point 4-20mA Output Card. What I am using is a 16 point relay card. My question is - can I manipulate the common supply current through the relays to proportionally control these solenoids or will opening and closing the relays change the circuit? The shoes are not all on at the same time but all operate at the same pressure. The solenoids are directly moving the shoes - not a valve with pneumatics or anything like that. The Kuhnke equipment is 657.452.68 and 657.452.69 - if anyone would happen to know anything about these. I called Kuhnke USA (Ellis Kuhnke) and they couldn't tell me anything about them.

[JRoss 84]

A 16-point relay card is off/on, and cannot be used to replace an analog output card, unless you are changing the control of your machine. AB does make 4-point 4-20mA output cards, so you'll have to use enough of those to cover your needs.