Armfield Instruction Manual
94
Fixed (manually set) ratio
In the PCT40 software, select ‘Control’ to open the PID controller window.
Set P, I and D to 0.
In Manual Control set the percentage time during which the control valve will be
open. 50% is suggested as a starting value
At the bottom left, set the Cycle Time to 10s- this is the time over which the control
percentage will be applied (i.e. for a percentage of 50% and a cycle time of 10s, the
valve will be switched on for 5s and switched off for 5s).
Select the Manual Control radio button and click on ‘Apply’. The valve should begin
to operate intermittently as the time proportional controller sends signals to control it.
Close the drain valve at the base of the large process vessel, preventing flow out of
the vessel. The vessel will begin to fill with water. When the fluid level reaches
200mm, partially open the valve to allow water to drain slowly from the vessel.
Check that there is a new data sheet for data logging.
Select the
icon to begin data logging, and observe the fluid level in the process
vessel. When the level has changed by more than 50mm, select the
icon to
finish data logging.
Adjust the control percentage according to the change in fluid level. If the fluid level
fell, decrease the percentage. If the level rose, increase it. If the change was rapid,
make a change of 15 to 20%. If it was gradual, change the value by 5 or 10%.
Continue to monitor the fluid level and adjust the percentage value until the fluid
maintains a constant level.
Create a new results sheet by selecting the
icon in the tool bar of the software.
Select the
icon to begin data logging, and log the fluid level for a few minutes.
Select the
icon to finish data logging.
Make a note of the settings used.
On the software screen, select the control switches for valve SOL3, opening the
valve and allowing water to drain from the vessel until the water level is
approximately 150mm.
Close SOL3 again.
Create a new results sheet by selecting the
icon in the tool bar of the software.
Controller-controlled time proportioning
In the PCT40 software, select ‘Control’ to open the PID controller window.
Set the Set Point to 200mm.
Set P to 100%.
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