5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 123 © 2002-2007 DH Instruments, a Fluke Company
When the PPC3 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 transducer readings,
c) PA and 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 PPC3 is delivered with PA and PM values set to zero and 1 for all
ranges. This does not mean that the PPC3 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
(for absolute
mode calibrations if 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
an be viewed by pressing [SPECIAL], <8cal>, <1view>.
The current value of gauge mode P
offset
can be viewed by pressing [SPECIAL],
<1AutoZ>, <2view>.
A new PPC3 is delivered with PA and PM values set to zero and 1 for all
ranges. This does not mean that the PPC3 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 PPC3 Q-RPTs are DHI PG7000 gas operated
piston gauges (PG7201, PG7202, PG7601). Contact DHI for additional information.
Gas operated piston gauge (deadweight tester), with the following characteristics:
• Measurement uncertainty of ± 0.0025 % of reading for Standard Class Q-RPTs or
± 0.002 % of reading for Premium Class Q-RPTs. A standard with higher measurement
uncertainty may be used but PPC3 measurement uncertainty may be degraded
proportionally from published specifications.
• If the Q-RPT is an Axxx (absolute) type and will be used in the absolute and/or
negative gauge measurement modes, the reference must be able to apply absolute
pressures: Absolute pressures may be arrived at either by operation relative to an
evacuated bell jar or, for higher pressures, by addition of atmospheric pressure
measured by a high accuracy barometer. Axxx (absolute) Q-RPTs that will not be
used in absolute of negative gauge measurement modes (as is very often the case
for higher pressure Q-RPTs) do not require the application of absolute pressure for
calibration and may be calibrated using a gauge pressure standard.
Axxx (absolute) Q-RPTs calibrated in gauge measurement mode by applying gauge
reference pressure values should be used in gauge mode only (see Sections 3.3.3,
PRINCIPLE, 5.2.5).
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