Armfield Instruction Manual
178
When the pump operates, carefully close the lid of the pump, ensuring that the tubing
is not pinched by the lid.
Check that water is now drawn through the pump to drain
Set the speed of pump B to 0%
Click on the PID controller for pump A
Select the Manual Control radio button in the top right section of the PID control
window
In the bottom right section, set the pump speed to 50%
When the pump operates, carefully close the lid of the pump, ensuring that the tubing
is not pinched by the lid.
Check that water is now drawn through the pump to drain
Set the speed of pump A to 0%
Set the PID values for the controller in the appropriate boxes in the software.
Suggested starting values are a Set Point of 700ml/min, Proportional Band (P) of 5%,
Integral Time Constant (I) of 0s and Differential Time Constant (D) of 0s.
In the Sample/Configure… menu, set the software to log at intervals of 1 second.
If the signal oscillates too much (there is too much noise) to be able to easily control
the flow rate, it may be necessary to use filtering in order to average out the signal.
Filtering can be set in the Options menu under ‘IFD Sampling Parameters’.
Depending on local conditions, Linear or Constant filtering is probably the most
appropriate, but if this delays the response too much then Exponential may be a
better choice.
Select the
icon to begin data logging.
Log the flow rate until it settles to within a narrow range of the set point, then select
the
icon to stop logging.
Disturbances
Within the software, it is possible to introduce a disturbance to the flow rate by
altering the speed of pump B:
In the software, select the
icon to create a new results sheet.
Select the
icon to begin data logging.
In the software, change the speed of pump B to 10%.
Log the flow rate as the PID controller adjusts to the changed flow rate through the
orifice. Wait until the flow rate settles to a steady value.
Change the speed of pump B to 20%. Wait until the flow rate settles to a steady
value.
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