Flow vision FC 01- CA, User Manual

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FC 01- CA | Flow Meter
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DESCRIPTION
Major benefits of this method are:
– Fast response, particularly to sudden flow standstill.
– Medium temperature measurement, providing optimum temperature compensation.
– Increased safety because the sensor cannot be overheated during flow standstill.
The flow rate is determined by mass flow.
1 .1 .2 Physical principles of gas measurement
With the exception of Coriolis meters and calorimetric flow meters, flow meters used for gas meas-
urement are pure volume flow meters that require density
ρ
to determine mass flow Q from the
volume flow measured:
Q = V x
ρ
Coriolis meters are used for higher mass flow quantities and higher densities only, where density
is directly proportional to pressure and inversely proportional to temperature (related to absolute
Kelvin scale).
The quantity required in general practice is mass flow as it indicates the exact gas quan-
tity, whereas volume flow only defines the volume the gas has adopted during the measurement
procedure.
1 .1 .3 Standard and operating volume flow
Standard volume flow
The calorimetric measuring procedure measures the existing standard volume flow or mass flow
without requiring additional pressure and/or temperature measurements. Like velocity changes,
pressure fluctuations cause fluctuations in standard volume flow which are indicated as such. The
standard volume flow indicated relates to 1,013 mbar/ 14.89 PSI and a temperature of 0 °C.
Operating volume flow
The standard volume flow value is converted into operating volume flow by means of the “ideal
gas equation”:
with P being pressure, V the volume and T the temperature (related to the absolute Kelvin scale).
The pressure to be set on the electronic control unit FC01-CA and the current temperature measured
are taken into account and used as a basis. Calculating operating volume flow is only reasonable when
pressure is known and constant.
The assigned velocity rates (averaged on the pipe section) are converted from standard conditions
to operating conditions the same way as volume flow.
P x V
T
= Konstant