Physical Principles Of Gas Measurement; Standard And Operating Volume Flow - Flow vision FC100 - CA User Manual

Major benefits of this method are:
• Fast response, particularly in the event of a sudden complete flow stoppage.
• Medium temperature measurement, providing optimal temperature compensation.
• Increased safety because the sensor cannot be overheated during flow standstill.
The flow velocity 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
measured volume flow V:
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 quantity,
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 1013 mbar/14.69 psi and a temperature of 0 °C/32 °F.
Operating volume flow
The standard volume flow value is converted into operating volume flow by means of the "ideal gas
law":
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 FC100-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 cross section) are converted from standard conditions
to operating conditions the same way as volume flow.
FC100-CA | Flow Meter
DESCRIPTION
Q = V x ρ
P x V
= constant
T
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