Exercise E
73
Select ‘Configure’ from the Sample menu, and set sampling to Automatic at intervals
of 5 seconds, with duration as Continuous.
Fixed (manually set) ratio
In the PCT40 software select ‘Control’ below the Tank Level sensor display, to open
the PID controller window.
Set P, I and D to 0.
In Manual Operation set ‘Manual Output’ to 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).
Set the Mode of Operation to ‘Manual Control’ 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 valves SOL2 and SOL3,
opening the valves and allowing water to drain from the vessel until the water level is
approximately 150mm.
Close SOL2 and SOL3 again.
Create a new results sheet by selecting the
icon in the tool bar of the software.
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