Aalborg GFC - Manual (Page 19)

7. CALIBRATION PROCEDURES
NOTE: Removal of the factory installed calibration seals and/or any
adjustments made to the meter, as described in this section, will void
any calibration warranty applicable.
7.1 Flow Calibration
Aalborg
7 Instruments' Flow Calibration Laboratory offers professional calibration
support for Mass Flow Meters and Controllers, using precision calibrators under
strictly controlled conditions. NIST traceable calibrations are available.
Calibrations can also be performed by customers using available certified stan-
dards.
Factory calibrations are performed using state of the art NIST traceable precision
volumetric calibrators.
Calibrations are performed using dry nitrogen gas. Calibration can then be cor-
rected to the appropriate gas desired based on relative correction [K] factors
shown in the gas factor table - see Appendix 2. A reference gas, other than nitro-
gen, may be used to approximate the flow characteristics of certain gases closer.
This practice is recommended when a reference gas is found with thermodynam-
ic properties similar to the actual gas under consideration. The appropriate rela-
tive correction factor should be recalculated - see section (9).
It is standard practice to calibrate Mass Flow Controllers with dry nitrogen gas. It
is best to calibrate the GFC transducers to actual operating conditions. Specific
gas calibrations of non-toxic and non-corrosive gases are available at specific
conditions. Please contact your distributor or Aalborg
7 for a price quotation.
It is recommended that a flow calibrator of at least four times better collective
accuracy than that of the Mass Flow Controller to be calibrated be used.
Equipment required for calibration includes a flow calibration standard and a cer-
tified high sensitivity multimeter (which together have a collective accuracy of
±0.25% or better), an insulated (plastic) screwdriver, a flow regulator (example:
metering needle valve) installed upstream from the Mass Flow Controller and a
pressure regulated source of dry filtered nitrogen gas (or other suitable reference
gas).
The gas and ambient temperature, as well as inlet and outlet pressure conditions
should be set up in accordance with actual operating conditions.
15
,