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RPM4/HPMS A70M/A20M-AF OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company Page 110
5.3.4 RECOMMENDED CALIBRATION POINT SEQUENCE
Calibration adjustments to RPM4 Q-RPTs are made by altering calibration coefficients,
PA and PM (see Section 5.3.1.1). To adjust these coefficients to optimum values giving the
best results over the Q-RPTs’ complete operating range, the specific calibration point
sequence defined in Table 20 is recommended.
Prior to running the calibration point sequence, the Q-RPT should be exercised:
a) Set full scale pressure.
b) Dwell at full scale pressure for 5 minutes.
c) Return to atmospheric pressure (vented).
d) Dwell for ten (10) minutes.
A dwell time of 60 seconds is recommended before taking data at each pressure increment.
The calibration pressure standard is not required to apply precisely the nominal pressure
value of each calibration point as long as the exact value of the applied pressure is known. Best
results are obtained if the actual applied pressure is within 5 % of the recommended nominal
point.
Table 20. Calibration point sequence for A20M and A70M Q-RPTs
CALIBRATION
SEGMENT
POINT
NO.
POINT
[% OF SPAN]
1 Atmospheric pressure
2 25 %
3 50 %
4 75 %
Ascending
5 100 %
6 75 %
7 50 %
8 25 %
Descending
9 Atmospheric pressure
A Q-RPT that will NOT be used in absolute measurement mode after calibration may be
calibrated in gauge measurement mode with a gauge pressure standard. The Q-RPT should then
be used in gauge mode only (see Sections 3.3.3, PRINCIPLE, 5.3.5).
5.3.5 TURNING OFF ABSOLUTE MODE CAPABILITY FOR A Q-RPT
PURPOSE
To prevent operation in absolute measurement mode on a Q-RPT that has been calibrated
for gauge mode only.
PRINCIPLE
RPM4 A70M/A20M Q-RPTs are frequently used in gauge measurement mode only (see
Section 3.3.3, PRINCIPLE). Q-RPTs that are used in gauge mode only, may be calibrated
in gauge mode with a reference that applies gauge pressures. Calibration with an absolute
reference is not necessary. However, if a Q-RPT is calibrated in gauge mode, it is not
possible to know if it is in or out of tolerance in absolute modes. To avoid using absolute mode
with a Q-RPT that is calibrated for gauge mode only, access to absolute mode can be turned
OFF. This is accomplished in the [SPECIAL], <8cal> menu.