Calculation Of Flow Volume; Flow Limits - Kamstrup flowIQ 3100 Series Technical Description

TECHNICAL DESCRIPTION flowIQ® 3100

12.4 Calculation of flow volume

During flow measuring, the water meter passes through a number of sequences, repeated at fixed intervals.
Deviations only occur when the meter is in test mode.
The measurement of the actual velocity of sound in water is also used to determine the temperature of the
water, as there is a correlation between these two values, at temperatures below approx. 30 °C
The flow is calculated, as mentioned above, by multiplying the flow rate and the cross-sectional area:
= 
Q F A
This measurement and calculation is performed every four seconds in the meter; the calculation itself only takes
a few milliseconds. The measurement is therefore a 'snapshot' of the current flow.
This, like any type of digital sampling, integrates the measurements over time, leading to the calculation of the
final volume.

12.5 Flow limits

In the meter's working range, from 'minimum cut-off' to saturation flow (called 'maximum cut-off') the flow
through the meter will be registered with an accuracy which reflects legal requirements/OIML R49.
If the flow exceeds maximum cut-off, the meter registers a constant flow corresponding to 'max. cut-off '.
In practice, the highest possible water flow through the meter will be limited by the pressure in the installation, or
by cavitation due to too low downstream pressure.
If the flow value gets lower than 'minimum cut-off', the meter does not register any flow.
In the meter's working range, from 'minimum cut-off' to 'maximum cut-off', there is a linear connection between
the quantity of water, which has passed through the meter and the measured water flow.
According to metrological and technical requirements/OIML R49, the upper flow limit (Q4/Max flow) is the highest
flow at which the flow meter may operate for short periods, without exceeding maximum permissible error. The
meter has no functional limitations during the period, when the meter operates above this limit (Q ).
4
Please note, however, that high flow velocities > Q (Max flow) involve the risk of cavitation, especially at low static
4
pressures below 0.2 MPa (2 bar) after the meter.
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Kamstrup A/S • Technical Description • 5512-1242_N1_GB • 10.2019