5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 101 © 1998 DH Instruments, Inc.
OPERATION
The autozero by comparison at atmosphere routine builds in a three minute wait to allow
the reference transducers to stabilize. For best results, a one hour wait with the PPC2 AF
idle and at stable temperature before running the autozero routine is recommended.
To run the autozero routine for the Hi reference
transducer select 1AutoZ under 4Internal of the
SPECIAL menu. Then display is:
Autozero
1View 2Run
Select 2Run. The display is:
Autozero ref sensor
1Hi 2Lo
Select 1Hi. The display is:
Autozero Hi ref?
1000 psia
Press ENTER to confirm that you want to run the
autozero routine on the Hi reference transducer (whose
range is 1 000 psia). The next display is:
Hi ref autozero
by comp at atm
Press ENTER to confirm that the autozero routine used
will be the comparison between the Hi and Lo reference
transducers at atmosphere. The next display is:
ENTER when autozero
port clear & vented
Assure that the AUTOZERO port on the rear panel of
PPC2 AF is unobstructed and exposed to atmospheric
pressure. Once this has been verified, press ENTER.
The next display is:
14.0233
seeking autozero
The current pressure (in current pressure units) is
displayed with "seeking autozero" flashing while PPC2
AF operates internal valves to connect the Hi and Lo
reference transducers together and to the
UTOZERO port and runs a pressure stability test.
When the stability test has been met the next display is:
Collecting autozero
Wait 180 seconds
The 180 counts down to zero as PPC2 AF collects readings from the two reference transducers:
The next display is:
1. New value of PA(z)net based on the PA(z)raw just measured.
2. Value of PA(z)net currently in use.
New PAzNet -59 Pa
Old PAzNet -11 Pa
If the autozero routine is being run as part of the calibration, the final result will be new
and old PA(z)tare, not PA(z)net (see Section 5.4.4.5).
Pressing ENTER causes New PAzNet to replace the PAzNet value currently in use (Old PAzNet).
Pressing ESCAPE returns to the autozero menu without changing the current value of PA(z)net.
Old PAzNet remains active and New PAzNet is lost.
PA(z)net = PA(z)raw - PA(z)tare (see Section 3.4.4.1.)
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