Armfield Instruction Manual
116
Take a second length of tube with a quick-release fitting at one end and a drain valve
at the other. Connect this end to the other side of the coil, and direct the opposite end
of the tube to a suitable drain. Open the drain valve at the end of the tube.
Check that the drain valve on the end of the plinth is open and that it is connected to
a suitable drain.
Procedure
SAFETY NOTE: During this exercise the apparatus may reach temperatures hot
enough to cause burns or scalds. Do not touch the process vessel during the
exercise, or remove the coil or sensors from within the vessel. Allow the apparatus to
cool before draining the water or disconnecting any of the tubes from the process
vessel.
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 heater will be on. 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
heater will be switched on for 5s and switched off for 5s).
Select the Manual Control radio button and click on ‘Apply’. The heater should begin
to operate intermittently as the time proportional controller sends signals to control it.
Check that there is a new data sheet for data logging.
Select the
icon to begin data logging, and observe the temperature in the
process vessel, T1. When the temperature has risen by more than 20°C, select the
icon to finish data logging.
Adjust the control percentage according to the change in temperature. If the change
was rapid, reduce the time ‘On’ by 25 to 30%. If it was gradual, reduce the value by
10 or 15%.
Continue to monitor the temperature and adjust the percentage value until the
temperature 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 temperature for a few minutes.
Select the
icon to finish data logging.
Make a note of the settings used.
Open the Control window and set Mode of Operation to Off. Apply and close the
window.
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