Intelligent Flowmeters
Measuring with intelligent flowmeters
All the usual benefits associated with
intelligent instruments are potentially applicable to many types of
flowmeter. However, their availability in the market place is currently
very limited.
Intelligent differential pressure measuring instruments can be used to
good effect in conjunction with obstruction-type flow transducers. One
immediate benefit of this in the case of the commonest flow-restriction
device, the orifice plate, is to extend the lowest flow measurable with
acceptable accuracy down to 20% of the maximum flow value.
In positive-displacement meters, intelligence allows compensation for
the thermal expansion of meter components and temperature-induced
viscosity changes. Correction for variations in flow pressure is also
provided for.
Intelligent electromagnetic flowmeters are also available, and these
have a self-diagnosis and self-adjustment capability. The usable
instrument range is typically from 3% to 100% of full-scale reading and
quoted accuracy is ±0.5%. It is also normal to include a non-volatile
memory to protect constants used for correcting for modifying inputs,
etc., against power supply failures.
Intelligent turbine meters are able to detect their own bearing wear and
also report deviations from initial calibration due to blade damage,
etc. Some versions also have a self-adjustment capability.
The trend is now moving towards total flow computers which can process
inputs from almost any type of transducer. Such devices allow the input
of parameters like specific gravity, fluid density, viscosity, pipe
diameters, thermal expansion coefficients, discharge coefficients, etc.
Auxiliary inputs from temperature transducers are also catered for.
After processing the raw flow transducer output with this additional
data, flow computers are able to produce measurements of flow to a very
high degree of accuracy.
More Flow Measurements
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