3. OPERATION
Page 61 © 2002-2007 DH Instruments, a Fluke Company
• 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 atmospheric pressure to
the PPC3 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 PPC3 to stabilize at atmospheric pressure
and ambient temperature for 10 to 15 minutes before running AutoZ.
OPERATION
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 PPC3 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 PPC3.
To access the PPC3 AutoZ function menu press [SPECIAL], <1AutoZ>. The display is:
1. Active Q-RPT designator.
2. Indication of active measurement mode (<abs> for absolute,
<gage> for gauge and negative gauge).
3. Indication of whether AutoZ is currently ON or OFF for this
Q-RPT and measurement mode.
1off 2view IH
3edit 4run abs ON
• Select <1off> (or <1on>) to change the AutoZ status for the current Q-RPT and
measurement mode from ON to OFF or vice versa.
AutoZ ON is indicated by a <z> in the MAIN RUN screen, top line, fourth character
from the right. When AutoZ is OFF, the character is blank.
• Select <2view> to view the current value of P
offset
for the active Q-RPT and measurement
mode.
P
offset
should be zero for Axxx Q-RPTs when the PPC3 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.
• Select <3edit> to edit the value of P
offset
for the active Q-RPT and measurement mode
(see Section 3.5.1.1).
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