Analog Ramping

The application I am working on calls for the analog out (10vdc) be ramped (variable).

So, if the program calls for 350 tons of pressure from 0 to 5 volts over 15 minutes then steady pressure until the dwell time is complete.

This variable (ramp) changes from part to part as well as pressure and dwell.

This is not a pid loop, the loop closure is done at the servo valve (air operated) with transducer on the hydraulic side.

Air over oil booster

The application is almost complete and the servo works fine.....with the exception of the ramping of the analog.

I have asked this before in the forum but didn't undertand the replies.

Idec Pentra.......

Thanks in advance

Take a timer, and use the growth a function of Acc/Preset.

Should give you a growing ratio from 0 to 100%.

I can't find any variable like that in the analog module otherwise I would have.

I will look again.........Thanks

What PLC are you using?

sorry I see idec now

In the pulse instruction set they have ramp variables, but looks to apply only to pwm applications.

Thanks

Take any old timer (assuming you can read the current accumulated time).

Let it run.

Divide the accumulated value by the preset (store the resultant as a float).

Multiply that by your desired maximum output.

Done.

Ex: A timer with a timebase of 0.1 seconds, to finish at 15 minutes, requires a preset of 9000.
As it times, the accumulated time ramps up from 0 to 9000 (AB Timers).

ACCUM_TIME / PRESET_TIME = Some_Floating_Point_Value (which ranges from 0 to 1.0)

Current_Output_Value = Some_Floating_Point_Value * Maximum Output_Value

-- edit --
Ignore the ramp settings in the pulse output. Just feed your desired output into the pulse output control register.