DH Instruments PPC4, Руководство по эксплуатации и обслуживанию

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PPC4™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company Page 40
Table 7. AutoZ ON and OFF
Q-RPT
TYPE
MEASUREMENT
MODE
AutoZ
STATUS
P
offset
APPLIED
ΔP
atm
APPLIED
AutoZ
ROUTINE
RUNS
Axxx
(or utility
sensor)
Absolute
ON YES
Not Applicable
When initiated
by operator
OFF NO Not available
Gauge or
negative gauge
ON
YES
YES Automatically
when PPC4 in
VENT condition
OFF NO
Gxxx
or
BGxxx
Gauge or
negative gauge
ON YES
Not Applicable
Automatically
when PPC4 in
VENT condition
OFF NO No
Recommendations for the Use of the AutoZ Function
The AutoZ function provides a powerful and easy to use tool for improving the stability over
time of PPC4 internal and external Q-RPTs and maximizing the recalibration interval by
compensating for change in zero between full recalibrations. The following simple
recommendations will help ensure that you use this feature to best advantage.
•
In gauge measurement mode: Always leave AutoZ ON when operating.
•
In absolute measurement mode: Always leave AutoZ ON when operating if the AutoZ
routine has been run regularly using a valid P
offset
reference.
•
In absolute measurement mode: Run AutoZ at least every 30 days or when PPC4 has
been exposed to temperature changes exceeding 15 ºC (36 ºF).
•
In absolute measurement mode: Run AutoZ only when a reference whose
measurement uncertainty is known to be significantly better than that of the Q-RPT to be
AutoZeroed is available. Keep range ratios in mind when comparing uncertainty.
A ± 0.01 % FS barometer is roughly 10 times better than an ± 0.01 % 1 MPa (150 psi)
Q-RPT because the Q-RPT/barometer pressure ratio is 10:1. The measurement
uncertainty comparison should be made at 30 % of span for both
standard class and
premium class Q-RPTs. Though it may not be practical, the best possible reference with
which to run AutoZ in absolute measurement mode on Q-RPTs of A350K or lower, is a
gas operated piston gauge (such as a
DHI PG7601) applying a pressure near 100 kPa to
the PPC4 test port. The best day to day reference is a properly calibrated DHI RPM4 with
a BA100K or A100K Q-RPT.
•
In absolute measurement mode: Allow the PPC4 to stabilize at atmospheric pressure
and ambient temperature for 10 to 15 minutes before running AutoZ.
Note
•
The AutoZ function and values are Q-RPT AND measurement mode
(gauge/negative gauge or absolute) specific.
•
When AutoZ is run for an external Q-RPT in an RPM4, the PPC4 causes
the RPM4 to run its own AutoZero routine. The RPM4 Q-RPT is then
AutoZeroed as if it had been AutoZeroed independently of the PPC4.
•
P
offset
should be zero for Axxx Q-RPTs when the PPC4 is new or has just
been calibrated. P
offset
should be roughly equal to atmospheric
pressure for an Axxx (absolute) Q-RPT operating in gauge mode.
•
The value of P
offset
is always displayed and entered in Pascal (Pa).
Normally, in day to day operation, the value of P
offset
is changed by
running AutoZ (see Section 5.7.5.1 for Advanced Interface or Section
4.5.1.2 for Basic Interface), not by direct editing.