PPC2 AF OPERATION AND MAINTENANCE MANUAL
© 1998 DH Instruments, Inc. Page 104
1. New value of PA(z)net based on the PA(z)raw just measured.
2. Value of PA(z)net currently in use.
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).
New PAzNet 4.2 Pa
Old PAzNet 7.9 Pa
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)
AUTOZERO BY VACUUM ERRORS
1. For autozero to proceed when "seeking autozero", a pressure rate of change of less
than - 0.2 Pa/second as measured by the Lo reference pressure transducer, must
have been established. If the rate of change test is not met within 300 seconds,
then "Autozero error: vacuum rate timeout" will be displayed. Press ESCAPE or
ENTER to return to the autozero menu. Correct the leak or other problem with
vacuum source and retry.
2. If the value of PA(z)net resulting from the current autozero routine exceeds ± 0.15 %
of full scale of the Lo reference pressure transducer (0.075 psi, 0.5 kPa), the
PA(z)Net value determined will be displayed with the message, "ERROR: data
rejected". A PA(z)net greater than ± 0.15 % F.S. is assumed to indicate improper
autozero conditions, faulty calibration or damage to the Lo reference transducer.
Press ENTER or ESCAPE from this error to return to the autozero menu.
3. If the value of PA(z)net resulting from the current autozero routine exceeds ± 0.015 % but
is less than ± 0.15 % of full scale of the Hi reference pressure transducer (0.0075 psi,
0.05 kPa), the PA(z)Net value determined will be displayed with the message,
"WARNING: high value". A PA(z)net greater than ± 0.015 % F.S. may indicate improper
autozero conditions, faulty calibration or damage to the Lo reference transducer.
Press ENTER to proceed to the "New PAzNet/ Old PAzNet" screen or ESCAPE to
return to the autozero menu.
The autozero by vacuum routine is always run in range L3 but the results are used to
readjust PA(z)net for all the ranges of the Lo pressure reference transducer.
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