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Setpoint Ramping Tutorial

Alicat controllers come equipped with a setpoint ramping feature that allows them to ramp up and/or down to changes in setpoint, commonly used to ensure safety. With setpoint ramping, you can set a maximum speed at which a mass flow or pressure controller flows until the setpoint is achieved.

Setpoint ramping can also be configured to only apply to flow/pressure in a single direction for situations where you may need to quickly zero pressure or flow during an emergency.

To enable and edit the setpoint ramp functionality on your device through the display, follow the instructions below.

For further directions on units without a display, or to enable over serial, see the standard manual, the CODA Coriolis manual, or BASIS MEMS thermal manual.

10v Firmware

To activate setpoint ramping, set a maximum ramp rate and configure when to enable the ramping function.

SELECT: MENU > CONTROL > Setpoint Ramp

  • Ramp changes the maximum rate of change.
  • Units changes the engineering units used.
  • Set By Delta / Time allows for more detailed control of the ramp rate including changing the value of the time period.

Ramping options control when ramping occurs. This can be when the setpoint changes, when the device powers on, or when setting a zero setpoint.

  • Ramp Up can toggle between on and off. When off, the ramp rate will not be honored when increasing flow or pressure to reach a given setpoint.
  • Ramp Down can toggle between on and off. When off, the ramp rate will not be honored when decreasing flow or pressure to reach a given setpoint.
  • Power Up toggles between Allow Ramp and No Ramp. If set to No Ramp, the device ignores the ramp rate just after powering on, otherwise it honors the ramp rate starting at a zero setpoint. This functions the same as power-up setpoint with ramping. Changing one overwrites the other.
  • 0 Setpt determines if the controller ramps when a zero setpoint is set. If this setting is set to No Ramp when given a zero setpoint, the controller immediately moves to the zero setpoint. Otherwise, the controller ramps at the selected rate.

Older Firmware

9v firmware

Enabling the Setpoint Ramping Function

SELECT: MENU >  CONTROL > ADV CONTROL > CONTROL OPTS > RAMP ENABLE.

Your controller enables the ramping function independently for changes that require increases or decreases to achieve the new setpoint. For example, you can enable ramping up to a flow setpoint to prevent flow from building too quickly, but disable ramping down so that you can stop flow immediately. Each direction toggles on and off.

Setting a Maximum Setpoint Ramp Rate

SELECT: MENU > CONTROL > SETPT RAMP

Press DELTA to define the maximum allowable change in flow rate or pressure. Press TIME to define the amount of time within which that change occurs. The controller will display the resulting maximum ramp rate in the center of the display.

Enabling setpoint ramping overrides

The MORE OPTS button in the Ramp Enable Menu lets you set up overrides for the ramping function for two independent scenarios:

  • POWER ON applies an override where the controller ignores any enabled ramping whenever it is powered on. If it had a non-zero setpoint when it was turned off, it immediately
    reapplies this former setpoint. All setpoints after power up honor the enabled ramping options. This override is indicated by “Setpt at power on is instantly applied”.
  • ZERO CMD applies an override where controller ignores any enabled ramping whenever a 0 setpoint has been commanded. This override is indicated by “Zero setpt command instantly zeroes”.
8v firmware

Video tutorial

Step-by-step instructions (front panel)

  1. Press the bottom right button for “MENU” selection.
  2. Press the top left button for “CONTROL” selection.
  3. Press the top left button for “SETPT RAMP” selection.
  4. Press the top left button for “DELTA” selection.
  5. Use the up, down, and select digit buttons to set your desired delta.
  6. Press the bottom right button for “SET” selection.
  7. Press the top right button for “TIME” selection.
  8. Use the up, down, and select digit buttons to set your desired time.
  9. Press the bottom right button for “SET” selection.
  10. Press the top middle button for “TIME UNITS” selection.
  11. Use the up and down buttons to select your desired time units.
    1. Note:  This will NOT change the rate, and it will automatically update the current rate to the newly selected units.
  12. Press the bottom right button for “SET” selection.
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