Armfield Instruction Manual
60
Procedure
NOTE: The differential level switch must be primed before use. Priming is described
as part of this experimental procedure.
Switch on mains power to the console. The apparatus should not be left unattended
once in operation. Manual operation of the inlet pressure regulator and drain valve
should be used to control the fluid level if the vessel volume reaches the overflow
pipe, or the drainage channel in the plinth becomes full of water.
Run the PCT40 software and select Section 1: Level Control (inflow). Select the
icon to view the mimic diagram screen.
Loosen the locking nuts at the top of the differential level switch electrodes and
adjust the height of the rods to suitable starting values. It will be easier to refer the
values to the ruler mounted between the rods than to the scale on the side of the
vessel. Initial values of 20mm for the blue-topped rod and 50mm for the red-topped
rod are suggested (the red rod should be positioned higher than the blue rod).
Partially close the drain valve at the base of the large process vessel, limiting flow out
of the vessel.
In the software, check that data logging is set to automatic at intervals of five
seconds.
Prime the differential level switch
The logic for the differential level switch requires the sensor to be prepared ready for
use before it can be used to control the flow level.
Adjust the level switch (float switch) until the float is higher than the lower of the two
electrodes on the differential level switch.
In the On/Off – Solenoid 1 box, select the radio button for ‘Level (Float) Switch’.
Check that water begins to flow into the process vessel, and that the reading L1 is
varying with the rising water levels.
Allow the water level to reach the lower electrode on the differential level switch.
Lower the level switch and allow the water level in the vessel to drop.
Once the level is at least 50mm below the lower of the two electrodes on the
differential level switch, select the radio button for ‘Differential Level’ switch control in
the On/Off – Solenoid 1 box. The differential level switch is now ready for use.
Select the
icon to begin data logging.
Observe that the large vessel fills with water until the fluid level reaches the
differential level switch. Note the height of the fluid level relative to the switch sensors
when SOL 1 is closed by the control software.
Note the fluid height relative to the switch when the control software opens SOL 1
again.
Continue logging until the oscillations in fluid level reach stable values for magnitude
(height) and duration. Select the
icon to finish data logging.
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