Exercise E
75
To change the inlet feed rate, adjust the pressure regulator on the inlet pipe of the
apparatus: Pull the knob outwards from the body of the regulator, turn the knob a
half-turn anticlockwise then lock the value by pushing the knob back in.
In the Manual Control section of the PID controller window, adjust the percentage
setting until a constant fluid level is maintained.
Alter the feed rate again by repeating the adjustment to the pressure regulator. Allow
the fluid level oscillations to stabilise again.
Continue to reduce the feed rate until the fluid level in the vessel no longer returns to
the set point level (the drain rate exceeds the inlet flow rate).
Select the
icon to finish data logging.
Cycle Time
Create a new results sheet by selecting the icon in the tool bar of the software.
In the software, set the cycle time to 5s.
Select the
icon to begin data logging.
Log the fluid level in the vessel for at least 2 minutes, and then select the
icon to
finish data logging.
Alter the cycle time again, to 20s.
Select the
icon to begin data logging.
Log the fluid level in the vessel for at least 2 minutes, and then select the
icon to
finish data logging.
Reset the cycle time to 10s.
Effect of Inlet and Outlet Flow Rates
Investigate the effect of an inflow rate greater than the outflow rate, and of an outflow
rate greater than the inflow rate.
Decrease the outflow rate by closing the drain valve in the base of the vessel, but do
not completely close the valve. This will decrease the outflow rate compared to the
inflow rate.
Select the
icon to begin data logging. Adjust the percentage of ‘On’ time to ‘Off’
time in the PID controls until a steady fluid level is achieved, continue to log for a
minute more, then select the
icon to finish data logging.
Create a new results sheet by selecting the
icon.
Increase the outflow rate compared to the inflow rate by fully opening the drain valve.
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