Setpoint Ramping

What is setpoint ramping?

Setpoint ramping is one of Alicat’s latest mainline functions. With setpoint ramping you can set a maximum speed at which a mass flow or pressure controller flows until the setpoint is achieved. Typically, ramps have been programmed through PLCs (programmable logic controllers), but Alicat has simplified this process by allowing you to perform this functionality through the front display or via serial command. And the setpoint is updated every millisecond so you never lose the speed you’ve come to associate with Alicat.

Why use setpoint ramping?

Setpoint ramping is a utility that can be used in many fashions. One of our customer’s more common usages for this feature is for safety or precautionary. Rather than allowing a volume to be instantaneously pressurized or a high flow rate to be immediately seen by a process, ramping allows for a more controlled, observable behavior. Setpoint ramping can also be configured to only be applied to a single direction which is useful in situations in which you may need to quickly zero pressure or flow during an emergency.

How to use setpoint ramping?

To access setpoint ramping from the main screen of the local display, select Menu, then Control, and Setpoint Ramp is located at the top left of the screen.

On the Controller’s Setpoint Ramp screen, there are three options:

  1. Setpoint Step (Delta)
  2. Time Units
  3. Total Time

Selecting your desired parameters will calculate your Current Max Ramp Rate on the screen. The units of Delta are decided by the device’s current engineering units.
The selectable time units are:

  1. Millisecond
  2. Second
  3. Minute
  4. Hour
  5. Day

The minimum time that can be set is 1 millisecond and the maximum time is 100 days (maximum 10 days through the front display). Keep in mind that the slower the ramp becomes, the available resolution also decreases. To disable setpoint ramp, set the ramp to zero or a negative number.

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