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3. OPERATION
Page 57 © 2007 DH Instruments, a Fluke Company
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 RPM4 Q-RPTs and maximizing the recalibration interval by compensating for zero
drift between full recalibrations. The following simple recommendations will help assure that
you use this feature to best advantage.
• In gauge mode: Always leave AutoZ ON. Use [AutoZ] to run AutoZ whenever RPM4 is
vented and displays a significantly non-zero value. Wait at least 2 minutes after venting before
running AutoZ.
• In absolute measurement mode: Always leave AutoZ ON. Use [AutoZ] to run AutoZ every
approximately every 30 days or when RPM4 has been exposed to a temperature change
exceeding 15 ºC (36 ºF). AutoZero the Lo Q-RPT against a barometer with measurement
uncertainty of ± 0.04 psi (275 Pa) or better (note that this is only 0.3% of atmospheric pressure
so a relatively low accuracy barometer is adequate). AutoZero the Hi Q-RPT against the Lo Q-
RPT. Wait 5 to 10 minutes before running AutoZero in absolute mode.
OPERATION
The AutoZ function and values are Q-RPT AND measurement mode (gauge or absolute)
specific.
To RUN the AutoZ routine that rezeroes the Q-RPT, use [AutoZ] (see Section 3.3.9).
To access the RPM4 AutoZ function press [SPECIAL], <1AutoZ>. The display is:
1. Active Q-RPT designator.
2. Indication of active measurement mode (<abs> for absolute,
<gage> for gauge).
3. Indication of whether AutoZ is currently ON or OFF for this
Q-RPT and measurement mode.
1off 2view Hi
3edit 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, third 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 in absolute measurement mode when the RPM4 is new or has just been
calibrated. P
offset
should be roughly equal to atmospheric pressure when the Q-RPT is in gauge
measurement mode.
Select <3edit> to edit the value of P
offset
for the active Q-RPT and measurement mode
(see Section 3.5.1.1).
The value of P
offset
is always displayed and entered in Pascal (Pa).