185
Exercise EE - Proportional pressure input with PID
control
Objective
To control the pressure drop across an orifice using PID control of a proportioning
solenoid valve.
Overview
Flow is directed through an orifice with the flow rate controlled using a proportioning
solenoid valve. This produces a pressure drop across the orifice, which is monitored
using a differential pressure sensor. The pressure sensor sends a signal to the
computer that is proportional to the differential pressure across the orifice, which is in
turn affected by the flow rate. The PID controller within the software monitors the
pressure signal and adjusts the PSV valve setting to reach and maintain the required
pressure across the orifice.
Equipment Required
PCT40 bench.
Equipment set up
Ensure that the apparatus has been set up according to the Installation section.
Check that the mains water supply to the apparatus is off and the pressure regulator
is set to minimum. The apparatus should be connected to a suitable PC with the
PCT40 software installed, using the grey USB cable provided.
Take a length of tube with a quick release fitting at both ends. Connect one end to
the socket on the PSV. Connect the other end to one of the sockets in the side wall
of the small process vessel.
Take a second length of tube with a quick-release fitting at both ends. Connect one
end from the outlet (left hand socket) of the gear pump to the right hand (P3) socket
on the manifold block.
Take a length of tubing with a Guest push fitting at one end and an open end at the
other. Connect the tubing to the right-hand connection at the back of the manifold
block, and direct the other end to drain.
Check that the drain valve on the end of the plinth is open and that it is connected to
a suitable drain.
To enable the gear pump to operate, the water level in the small process vessel must
be above the level sensor in the vessel. To fill the small process vessel with water, it
is possible to remove the lid and fill from the top. Care must be taken not to damage
the attachments on the lid. The preferred procedure for filling the vessel is as follows:
Close the drain valve at the base of the small process vessel.
Run the PCT40 software and select ‘Section 10: Pressure Control’.
In the software, set the PSV 0% and fully close the pressure regulator valve (Pull the
large grey knob on the pressure regulator away from the body of the regulator, and
turn the grey knob fully anticlockwise).
Turn on the mains water supply to the apparatus.
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