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5. MAINTENANCE, ADJUSTMENTS AND CALIBRATIONS
Page 125 © 2004-2007 DH Instruments, a Fluke Company
Run the recommended calibration point sequence for the Q-RPT (see Section 5.2.4).
Record the pressure applied by the standard and the RPM4 reading at each calibration
point. Dwell at least 60 seconds at each point after setting the reference pressure to
allow full stabilization The data recorded is the “as received” data for this calibration.
Enter the calibration pressures and RPM4 readings into a spreadsheet. Calculate the
“non-corrected” RPM4 readings by backing out the PA, PM and P
offset
(P
offset
in the case of
Axxx (absolute) Q-RPTs in absolute mode only, do not back out P
offset
for for gauge mode
calibrations) recorded in Steps
and above, following:
non-corrected reading = ((corrected reading - PA)/PM ) + P
offset
Perform a linear regression to find the offset and slope that best fit the non-corrected
RPM4 readings to the calibration standard pressures. The offset is the new value of PA,
the slope is the new value of PM.
Press [SPECIAL], <8Cal>, <1Hi RPT> or <2Lo RPT>, <2edit> and write the new
calibration date and the new values of PA and PM for the Q-RPT calibrated (see Section
5.2.7). If this is an Axxx Q-RPT and the calibration was performed in gauge mode, turn
absolute and negative gauge modes OFF to avoid their being used after the calibration.
Calculate as left data for the calibration if desired following:
as left reading = (non-corrected reading • new PM) + new PA
Perform additional verification pressure runs as desired.
5.3 ADJUSTMENT OF ON-BOARD BAROMETER
PURPOSE
To adjust the output of the on-board barometer (see Section 1.2.2.2).
RPM4’s that have only G100K or G200K Q-RPTs (no Axxx or G15K or BGxxx) are NOT equipped with an
on-board barometer.
PRINCIPLE
The on-board barometer output can be adjusted using PA and PM values in the same manner as
Q-RPTs (see Section 5.2.1.1).
The on-board barometer is a low accuracy sensor used only for measuring changes in atmospheric
pressure over short periods of time (see Section 3.2.2) and the line pressure for G15KK and BG15K
line pressure compensation. RPM4 measurement uncertainty does not depend on the measurement
uncertainty of the on-board barometer.
OPERATION
To edit the values of PA and PM for the barometer, press [SPECIAL], <8cal>, <3barometer>. Pressing
[ENT] steps through displays of the calibration date (YYYYMMDD) and PA and PM. In edit mode, the
values can be edited. Pressing [ENT] after the last screen activates the edited values.
To view the current output of the on-board barometer, press [SPECIAL], <7Internal>, <3baro>.