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Exercise S - Temperature input with on/off control
Objective
To control the temperature in a process vessel using an on/off controller connected
to a temperature sensor, by controlling power to a heating element.
Overview
The temperature within the process vessel is monitored using a thermocouple type
sensor. The output is sent to an On/Off controller that switches a heating element on
or off to maintain the required set point temperature within the vessel.
Equipment Required
PCT40 bench with small process vessel containing a heating coil.
Equipment set up
Ensure that the apparatus has been set up according to the Installation section. The
lid with heating coil should be in position on the small process vessel, with the coil
surrounding the heating element. The apparatus should be connected to a suitable
PC with the PCT40 software installed, using the grey USB cable supplied.
Switch on mains power to the apparatus.
Run the PCT40 software and select ‘Section 6: Temperature Control (direct
continuous heating)’.
Fill the small process vessel with water:
Using a length of tubing with a quick release fitting at both ends, connect the PSV to
the upper fitting on the side of the small process vessel. Ensure that the lower fitting
on the side of the process vessel is not connected.
Close the drain valve on the process vessel.
In the software, set the PSV to 100% and watch as the small process vessel fills with
water.
Wait until the coil inside the vessel is fully covered with water, then set the PSV to
0%.
Check that the drain valve on the end of the plinth is open and that it is connected to
a suitable drain.
Select a second length of tubing with a self-sealing fitting on one end and an open
end at the other, and direct the open end to a suitable drain. Connect the quick-
release fitting to the lower connection on the side of the small process vessel. Water
will drain from the free end. Half close the drain valve on the end of the tube.
In the software, increase the PSV value using the arrow keys until the water level in
the process vessel is stable and covers the coil. Adjust the drain valve so that the
water level in the vessel remains constant and covers the coil at a PSV setting of
approximately 50%. The apparatus should not be left unattended, to ensure the
process vessel does not overflow or run dry.
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