d/a

How would I ramp the d/a output in time (1-500 sec)? This is not a pid loop just a straight d/a 0-10vdc. I have it working now but need a little input on the best approach to this.

Thanks in advance

Dave

What PLC?

Dave

What PLC? you could use a timer or a counter using the acc/time as your SP with a LIM or max instruction

You say you have it working now?...how are you doing it? that may be the best way

VoltsOut = 10V * Elapsed_time/500 seconds.

If you have a 12 bit analog output that correlates to
Out = 4095 * Elapsed_time/500 seconds.

If you have a 16 bit analog output its
Out = 32767 * Elapsed_time/500 seconds.

If you are using an AB SLC500 or Micrologix you could use a timer and the SCP instruction.

TON T4:0 1.0 500 0
SCP T4:0.ACC 0 T4:0.PRE 0 32767 O:0.0

Sorry I should have mentioned its a 12 bit d/a Idec MM Pentra.

I have it working without the ramp.
700 tons=max pressure @10vdc.

The loop is closed at a servo volve so I do not need to worry about a pid loop just supply the command to the valve

Its on a press and if we call for 350 tons =5vdc we need to be able to ramp the output from 0-5 vdc over a variable amout of time to allow the pressure to build up slow.

Thanks for the replies