Armfield Instruction Manual
136
Set the PSV to 100%, allowing cold water to flow through the coil in the small
process vessel. When the temperature T1 has reduced to around 20 – 30°C, set the
PSV back to 0%.
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 30°C (If the mains water temperature is close to 30°C then a
higher Set Point should be chosen, e.g. 40°C).
Set P to 100%.
Leave I and D set to 0.
The Manual Control setting may be ignored.
Leave the Cycle Time at 10s.
Select the Automatic Control radio button and click on ‘Apply’. The valve should
begin to operate intermittently as the time proportional controller sends signals to
control it.
Select the
icon to begin data logging, and observe the temperature in the
process vessel. Note the behaviour of the heater as the temperature approaches the
Set Point. When the oscillations around the Set Point have settled, select the
icon to finish data logging.
Disturbances
Within the software it is possible to introduce disturbances in the temperature inside
the process vessel by changing the flowrate of water through the vessel:
In the software, select the
icon to create a new results sheet.
Select the
icon to begin data logging.
In the software, increase the PSV setting by 20%. Open the drain valve at the base
of the process vessel enough to balance the flow in and out of the vessel, so that the
fluid level in the vessel remains constant.
Log the temperature for 10 minutes.
Increase the PSV setting by a further 20%, and open the drain valve more to
maintain the fluid level within the vessel.
Continue to log the temperature for another 10 minutes, and then select the
icon
to finish data logging.
Set the PSV back to its original setting and close the drain valve.
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