Exercise J
95
Leave I and D set to 0.
The Manual Control setting may be ignored.
Leave the Cycle Time at 10s.
Select the Automatic Control radio button and click on ‘Apply’. The valve should
begin to operate intermittently as the time proportional controller sends signals to
control it.
Select the
icon to begin data logging, and observe the fluid level in the process
vessel. Note the behaviour of SOL 2 as the fluid level approaches the Set Point.
When the oscillations around the Set Point have settled, select the
icon to finish
data logging.
Disturbances
Within the software it is possible to introduce disturbances in the outflow from the
vessel by opening the Normally Closed solenoid valve SOL 3:
Create a new results sheet by selecting the
icon in the tool bar of the software.
Select the
icon to begin data logging.
In the software, select the switch to open valve SOL 3.
Leave the valve open until the fluctuations in fluid level have settled to a constant
oscillation.
Close valve SOL 3. Allow the fluid level oscillations to settle to their original values.
Select the
icon to finish data logging.
Set Point
Investigate the effect of changing the pressure at which the on/off controller operates:
Create a new results sheet by selecting the
icon.
In the software, alter the pressure switch set point to 100mm.
Select the
icon to begin data logging.
Continue logging until the oscillations reach constant magnitude and duration, then
select the
icon to finish data logging.
Repeat the procedure, altering the set point and recording the change in fluid level
until the oscillations reach stable values. Suggested values for the pressure switch
set point value are 150, 200 and 300mm. Remember to create a new results sheet
for each set of data.
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