Sometimes applications will require control of the process ‘upstream’ of the Alicat instrument (a traditional back-pressure control situation, for example). For these cases, the valve needs to be in the downstream position. Just make sure to let us know when you order, and we’ll take care of the rest. If you need to change a forward pressure controller to a back pressure controller, this can be done in the field in two steps, one physical and one digital.
This guide will help you perform the necessary changes required to ensure your Alicat functions properly. On devices with 7v firmware or earlier, this change will require serial communication with your device.
Step 1: Switch Valve Position
Unplug your Alicat device and follow the valve switching video for your size valve, then proceed to step 2.
- Your Alicat flow controller
- Razor blade or utility knife
T-8 Torx driver
- 3/32 and 7/64 Hex drivers
Step 2: Activate Inverse Control Mode
For forward pressure control, the valve will open more to increase pressure, and close more to decrease pressure. When controlling back pressure with the valve on the downstream side, the valve will need to do the exact opposite, close more to increase pressure and open more to decrease pressure. This functionality is called “inverse control mode” and can be enabled by adding 32768 to register 20 via the front panel or serial communication.