Exercise BB
175
Gradually turn the knob to adjust the pressure regulator setting until the flow rate F1
is approximately 1400ml/min. Clockwise rotation opens the valve (increases flow),
anticlockwise rotation closes the valve (decreases flow).
Depending on variations in the local water pressure, the flow rate figure may
oscillate.
If local water pressure is low then a lower value than 1400ml/min may be set. Where
this is the case, always set a value slightly lower than the maximum flow rate to
protect against spikes in pressure.
Push the knob back in to fix the setting.
NOTE: If the flow rate exceeds 1500ml/min then the flow meter may give a reading of
0ml/min. The flow meter is not designed to read flow rate values of greater than
1500ml/min. The regulator valve must be closed to reduce the flow below this value.
Carefully close the lid of the peristaltic pump, ensuring that the tubing is not pinched
by the lid, and check that water is now drawn through the tubing and out to drain.
Reduce the speed of pump B to 0%.
Select ‘Configure...’ from the Sample menu. Set data logging to Automatic at 5
second intervals with Continuous duration.
Prime pump A:
In the software, open valve SOL 1
Set the speed of pump A 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%
Manual control of flow rate
Check that the valve SOL 1 is open (on).
In the software, set the speed of pump A to 50%.
Select the
icon to begin data logging.
Monitoring the flow rate F1, adjust the speed of pump A to give a flow rate of
700ml/min, using the up and down arrows.
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.
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