Toro Micro-Master Series User Manual page 97

Flow Meter Operation
When a flow meter is enabled, it is always monitoring the allocated input to calculate the current flow
rate. If the flow meter detects flow, the flow meter is active. If the detected flow exceeds the
adjustable trigger value, the flow meter is triggered. When the current flow rate falls below the trigger
value, the flow meter becomes active, or untriggered. When the current flow rate becomes zero, the
flow meter is idle.
The flow meter uses an average, limits and time to calculate the current flow rate. When a pulse is
received on the allocated input, the flow meter calculates the exact flow rate. If this flow rate is within
the limits specified, the flow is averaged over the number of samples specified. This smoothes small
changes in the period between pulses. If the exact flow rate is outside the limits specified, the current
flow rate is set immediately to the new value. This may occur at a program's shift/group change, or
when programs start. When the flow stops, no more pulses will be received. The flow meter
calculates a decreasing current flow rate based on the time elapsed since the last pulse occurred.
When the elapsed time increases to a value greater than 5 times the last pulse period, the current
flow is set to zero. Using the average, limits and time to calculate the current flow rate produces a
flow rate measurement that is responsive to large changes in flow, without excessive fluctuations in
the displayed flow during flows of relative uniformity.
The flow meter operation is shown in Figure 63.
Flow Meter Parameters
Flow Meter Units
Flow units for a flow meter can be 'Litres', 'Litres x 10', 'Litres x 100', 'Kilolitres'.
Calibration
The calibration for a Flow Meter depends on the type of Flow Meter attached to the controller. For a
pulse Flow Meter, the calibration is defined as the number of pulses for each unit of volume, and is
specified by the Flow Meter manufacturer. For an 4-20mA Flow Meter the calibration is defined as
the number of units of flow at 20mA. The number of pulses per unit flow can be set to any value up
to 255. The total flow is updated every pulse by an amount calculated by units/calibration.
For example, if a pulse flow meter has a specified output of 1 pulse per kilolitre, the Flow Meter Units
should be set to 'Kilolitres', and the Flow Meter Calibration should be set to 1.
Note that it is possible to mix calibration units between the flow meter and the controller. For
example, if a pulse Flow Meter has a specified output of 1 pulse per 100 litres, the Flow Meter Units
could be set to 'Kilolitres', and the Flow Meter Calibration could be set to 10. This may assist in
setting runtime units for volumetric programs.
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Micro-Master Touch User Guide
Current flow > 0
Idle
Current flow = 0
Figure 63 - Flow Meter Operation Schematic
Current flow > trigger value
Active
Current flow < trigger value
89
Triggered
Ver 1.2, June 2014