What is gas flow calibration?
Gas flow calibration refers to the calibration of a
flow sensing device such as a flow meter or flow
controller by comparing its measurement against a
flow measurement reference. Typically, the device,
or unit under test (UUT), is pneumatically connected
in series with the flow reference so they measure
the same gas flow; then the indications of the two
devices are compared.
molbloc
™
/molbox
™
system components
Fluke Calibration’s molbloc/molbox gas flow
calibration system consists of molbloc flow elements
that connect to a flow terminal (either molbox1+ or
molbox RFM) so the terminal can use pressure and
temperature measurements from around the flow
element, combined with gas properties and prior
molbloc calibration data, to determine and display
the gas flow rate.
Mass flow vs. volume flow
A frequent topic of discussion and confusion
surrounding gas flow measurement is that of mass
flow versus volume flow. Flow meters and flow units
used for flow measurements are used to measure
and express either the amount of volume of gas or
the amount of mass (number of moles or molecules)
passing through the device. When performing a gas
flow calibration, it is nearly always beneficial to
use a mass flow reference measurement, because
the mass flow rate stays constant throughout a flow
system in steady state. Since gas is compressible,
the volume flow rate varies at different locations
in a flow system due to changes in density caused
by changing temperature and pressure. Fluke
Calibration molblocs are mass flow standards, which
allow reliable comparisons to other flow devices.
The molbox terminal is also able to calculate and
express the flow rate in terms of volume flow at
another point in the system to allow testing of
volume-based devices.
Gas flow calibration
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www.flukecal.com Gas flow calibration
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