All the usual benefits associated with intelligent instruments are applicable to most
types of flowmeter. Indeed, all types of mass flowmeter routinely have intelligence
as an integral part of the instrument. For volume flow rate measurement, 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 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 the full-scale reading and
the quoted maximum inaccuracy is š0.5%. 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 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 user 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.