5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 109 © 1998 DH Instruments, Inc.
As Received/As Left Data
Frequently, calibration reports require that as received and as left data be reported. The necessary
information to report as received and as left data on the calibration of PPC2 AF reference
pressure transducers can be obtained in several ways.
When the PPC2 AF on-board calibration procedure is used, as received data for each point is
displayed as the calibration points are being taken and can be recorded at that time. As left data
for any range that has been calibrated can be viewed in the Cal function (see Section 5.4.6).
In addition, knowledge of pressures applied, associated transducer readings and PA/PM and PA(z) net
values can be used to calculate as received/as left values. For example, reversing PA/PM on the
as left reference transducer readings provides the transducer readings with PA = 0 and PM = 1.
Then applying the as received PA/PM and PA(z)net values to the readings calculates "as received"
readings (the readings that the transducer would have made with the old PA/PM and PA(z)net).
It is recommended that "as received" values of PA/PM and PA(z)net be recorded for each
range prior to running the calibration. The current PA/PM can be viewed under SPECIAL,
4Internal, 2Cal, 1View. PA(z)net's current value can be viewed under SPECIAL, 4Internal,
1AutoZ, 1View.
5.4.2 EQUIPMENT REQUIRED
1. Gas operated piston gauge (deadweight tester): able to set absolute pressures at
20 % increments in the range to be calibrated.
It is not necessary that the calibration pressure standard used apply precisely the nominal
pressure value requested for a calibration point as long as the exact value of the applied
pressure is known. Best results will be obtained if the pressure actually applied is within
± 2 % of F.S. of the range being calibrated from the nominal increment. On the Lo reference
pressure transducer, a piston gauge able to set absolute pressures relative to a vacuum
reference must be used and the zero psia point should be set using the lowest accurate
pressure point of the piston gauge. On the Hi reference pressure transducer, if desired,
a gauge pressure piston gauge combined with an accurate barometer can be used to
determine the absolute pressures applied. In that case, atmospheric pressure can be
used as the zero point and the barometers reading as the pressure applied by the standard.
2. Vacuum pump, vacuum gauge and connecting hardware: Needed only if the Lo
reference transducer is being calibrated for performing the setting PA(z)net procedure
(see Section 5.2.2 for hardware specifications).
5.4.3 SET-UP AND PREPARATION
To set-up and prepare the PPC2 AF for calibration of a reference transducer:
1. Set the PPC2 AF on a stable surface near the calibration standard at as close as possible
to the calibration standard's reference height. Consider the connections that may need to
be made to the rear panel and access to the front panel display and keypad.
2. Connect a pressure supply greater than the maximum pressure to be applied during the
calibration to the PPC2 AF rear panel SUPPLY port (1/8 in. NPT F).
3. If the calibration will include pressures under atmospheric pressure, connect a vacuum pump
to the PPC2 AF rear panel EXHAUST port (1/4 in. NPT F). There will be a constant bleed of gas
through the EXHAUST port so the vacuum pump should be self-venting or disconnected when "off".
4. If the Lo reference pressure transducer is to be calibrated, install a 1/4 in. NPT M X KF16
adaptor (P/N 102519, provided with PPC2 AF accessories) on the PPC2 AF rear panel
AUTOZERO port and leave room for connecting and disconnecting the vacuum line.
Leave this port open to atmosphere.
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