DH Instruments PPCH-G, Руководство по эксплуатации и обслуживанию

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5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 125 © 2007 DH Instruments, a Fluke Company
5.2.1.2 AS RECEIVED AND AS LEFT DATA
Frequently, calibration procedures require that as received and as left data be
reported. The necessary information to report as received and as left data on the
calibration of PPCH-G Q-RPTs can be obtained in several ways.
When the PPCH-G CalTool calibration assistance software is used, as received
data is displayed while running the calibration and is automatically recorded and
provided if desired. As left data is also calculated and presented.
At any time, a) reference pressures applied, b) associated Q-RPT readings,
c) PA, PM and P
offset
values can be used to calculate as received and as left values.
For example, backing out PA and PM on the as left data yields the transducer
readings with PA = 0 and PM = 1. Then applying the as received PA and PM
and P
offset
values to the readings calculates as received readings (the readings
that the transducer would have made with the old PA, PM and P
offset
).
A new PPCH-G is delivered with PA and PM values set to zero and 1 for all
ranges. This does not mean that the PPCH-G has not been calibrated. In the original
factory calibration, privileged factory coefficients are used for calibration with the
user PA and PM set to zero and 1.
It is recommended that “as received” values of PA, PM and P
offset
(P
offset
for
absolute mode calibrations if AutoZero is used in normal operation) be recorded for
each range prior to running the calibration. The current PA and PM and absolute
mode P
offset
can be viewed by pressing [SPECIAL], <8cal>, <1view>.
A new PPCH-G is delivered with PA and PM values set to zero and 1 for all
ranges. This does not mean that the PPCH-G has not been calibrated. In the original
factory calibration, privileged factory coefficients are used for calibration with the
user PA and PM set to zero and 1.
5.2.2 EQUIPMENT REQUIRED
The recommended calibration standards for PPCH-G Q-RPTs is a DHI PG7202 gas
operated, liquid lubricated piston gauge. Contact DHI for additional information.
Piston gauge (deadweight tester),
with the following characteristics:
•
Measurement uncertainty of ± 0.005 % of reading or better
. A standard with higher
measurement uncertainty may be used but PPCH-G measurement uncertainty may be
degraded proportionally from published specifications.
•
If the Q-RPT will be used in the absolute measurement mode, the reference must
be able to apply absolute pressures:
In the range of pressure covered by PPCH-G,
absolute pressures are usually defined by adding atmospheric pressure measured by a
barometer to gauge pressure defined by a piston gauge.
PPCH-G Q-RPTs that will not be
used in absolute measurement mode may be calibrated using a gauge pressure
only.