5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 103 © 1998 DH Instruments, Inc.
OPERATION
The quality of the autozero by vacuum results are highly dependent upon use of the
correct hardware and proper execution. For best results, follow these recommendations
closely:
1. Use the 1/4 in. Male X KF16 adaptor (Part No. 102519) to make the vacuum connection
to the PPC2 AF AUTOZERO port.
2. Use a large diameter vacuum hose to connect the PPC2 AF AUTOZERO port to the
vacuum source.
3. When instructed to apply vacuum to autozero port, be sure to apply less than 5 Pa
(0.00075 psi, 40 millitorr) to the AUTOZERO port. Use a vacuum gauge with
accuracy of at least ± 10 % to measure the vacuum.
To run the autozero routine for the Lo reference
transducer select 1AutoZ under 4Internal of the
SPECIAL menu. Then display is:
Autozero
1View 2Edit 3Run
Select 3Run. The display is:
Autozero ref sensor
1Hi 2Lo
Select 2Lo. The next display is:
Autozero Lo ref?
50 psia
Press ENTER to confirm that you want to run the
autozero routine on the Lo reference transducer
(whose range is 50 psia). The next display is:
Lo ref autozero
by vacuum
Press ENTER to confirm that the autozero routine
used will be the application of vacuum to the
AUTOZERO port. 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.
PPC2 AF operates internal valves to trap atmospheric
pressure on the Lo reference transducer and isolate it
from the AUTOZERO port. The next display is:
Stabilizing
Wait 180 seconds
The 180 counts down to zero to provide a three minute
stabilization period for the Lo reference transducer.
The next display is:
ENTER when autozero
port at vacuum
Apply vacuum of 5 Pa (0.00075 psi, 40 millitorr) or less to the AUTOZERO port. Once the
vacuum is achieved, press ENTER.
When ENTER is pressed, the autozero Lo reference
transducer isolation valve opens and the display is:
14.0372 psi a
Seeking autozero
The current pressure (in current pressure units) is displayed while PPC2 AF seeks the
reference rate of change of pressure point. When the reference rate of change of pressure
has been achieved the display is:
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