Why things are they way they are.
I assume the amplifier is taking the voltage signal and giving the final power output to the valve.
Yes, the motion controller sends a ±10 volt signal to the amplfier or the on board electronics. The amplifier or OBE then powers the solenoid that moves the spool.
Peter using one of your systems the delta would be controller amp and everything in one package correct?
No, those valve amplfiers require a lot of current and the noisy PWM does not mix well with analog signals of a motion controller or PLC for that matter.
Our modern controllers output ±10 volts. This works well with most servo solenoid valves with amplifiers. Servo vavles require a voltage to current converter. These are relativiely simple devices where you select the current output for ±10 volts.
Our first generation controllers were similar to the QB module and could output current directly but this turned out to be not such a good idea. The power to drive the valve can't be drawn from the back plane so an external current source had to be connected to the controller. If there was any wiring mistakes the controller was toast and there were too many toasted boards ( wiring mistakes ). The boards often had the traces on the board burned out so there was no repairing them. Our second generation controller and the ones we made for PLCs used only ±10 volt output so no external power had to be connected to the motion controller. Now few boards get returned unless they hook AC power to something.
Any external amplifier cards should be mounted in a j box out by the valves so the wires between the amplifier cards to the valves are as short as possible and away from any analog feed back devices. You don't want high current, fast switching PWM running long distance because it will induce noise on any adjacent analog signal or feed back signals. It is best to get either servo valves or servo solenoid valves with on board electronics and not separate amplifiers. Separate amplifiers are not a good idea because they must also be tuned to provide the best spool response. OBE amplifiers come tuned for that particular valve which is good.
I once made a very expensive trip to India because the motion controller was being blamed for causing random and wild oscillations. The Moog 27/200 valves had separate amplifiers. After a day I suspected the amplifier card and finally I finally caught a graph of the system oscillating with the inputs to the amplifier shorted together. At this point only the amplifier or valve could be blamed. I asked the people in charge if the amplifiers had been tuned and the reply I got was "they have to be tuned?" I/we spent the next couple of days tuning amplifiers and everything was fine after that. ( at least the hydraulic control part )
The moral of the story is if you buy servo solenoid valves get the ones with on board electronics.
Delta would just need +/- 10 signal in? or 0-10 volt in and a digital input for direction extend / retract?
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Our controller would generate ±10 volts like the QB module to the amplfiler or valve if it has OBE. We just don't support the current output option for the reasons stated above.
You mentioned inputs and I thought we were talking about outputs.
Our controller has lots of options for feed back devices. Usually and old Temposonic rod start stop ( what we prefered ) or PWM or gated. QBs were usually used in PWM mode. Our controller can also use analog position feed back 4-20ma or 0-10v or ±10v or ±5 v. A modern option is to use SSI feedback. SSI is preferred because it is relatively noise immune and it provides high resolution feed back.
At this point it would be best to know exactly what you want to do and what kind of feed back device you are using.
