Dfm 36/37/46/47 Models; Calibration Procedures; Flow Calibration - Aalborg DFM 26 Operating Manual

6.2.3 DFM 36/46/37/47 Models
Unscrew the four socket head cap screws (two 10-24 and two 6-32) at the inlet
side of the meter. This will release the short square block containing the inlet com-
pression fitting. The 60 micron filter screen will now become visible. Remove the
screen. DO NOT remove the RFE inside the flow transducer! Clean or replace each
of the removed parts as necessary. If alcohol is used for cleaning, allow time for
drying. Inspect the flow path inside the transducer for any visible signs of con-
taminants.If necessary, flush the flow path through with alcohol. Thoroughly dry
the flow paths by flowing clean dry gas through. Re-install the inlet parts and fil-
ter screen. Be sure that no dust has collected on the O-ring seal. It is advisable that
at least one calibration point be checked after re-installing the inlet fitting - see sec-
tion 7.
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

Aalborg7 Instruments' Flow Calibration Laboratory offers professional calibration
support for Mass Flow Meters, using precision calibrators under strictly controlled
conditions. NIST traceable calibrations are available. Calibrations can also be per-
formed at customers' site using available standards. Factory calibrations are per-
formed using NIST traceable precision volumetric calibrators incorporating liquid
sealed frictionless actuators. Generally, calibrations are performed using dry nitro-
gen gas. The calibration can then be corrected to the appropriate gas desired based
on relative correction [K] factors shown in the gas factor table (see APPENDIX III).
A reference gas, other than nitrogen, may be used to better approximate the flow
characteristics of certain gases. This practice is recommended when a reference
gas is found with thermodynamic properties similar to the actual gas under con-
sideration. The appropriate relative correction factor should be recalculated (see
section 9). It is standard practice to calibrate Mass Flow Meters with dry nitrogen
F
gas at 70.0 F (21.1
let pressure. It is best to calibrate DFM transducers to actual operating conditions.
Specific gas calibrations of non-toxic and non-corrosive gases are available at spe-
cific conditions. Please contact your distributor or Aalborg7 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 Meter to be calibrated be used. Equipment
required for calibration includes: a flow calibration standard, PC with available RS-
485/RS-232 communication interface, a certified high sensitivity multi meter (for
F
C), 20 psia (137.9 kPa absolute) inlet pressure and 0 psig out-
30