DH Instruments PPC4, Operation And Maintenance Manual

Page: 207 / 228

7. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 195 © 2009 DH Instruments, a Fluke Company
Perform a linear regression to find the offset and slope that best fit the non-
corrected PPC4 readings to the calibration standard pressures. The offset is
the new value of PA, the slope is the new value of PM.
Select <Spec>, <Cal> , <Hi RPT> or <Lo RPT> , <edit> and enter the new
calibration date and the new values of PA and PM for the Q-RPT and range
calibrated. If this is an Axxx Q-RPT used in absolute mode, edit the value of
P
offset
to zero. If this is an Axxx Q-RPT and the calibration was performed in
gauge mode, turn absolute and negative gauge modes OFF to avoid their being
used after the calibration (see Section 7.2.5).
Calculate as left data for the calibration if desired following:
as left reading = (non-corrected reading • new PM) + new PA
Perform additional verification pressure runs as desired.
7.2.8.2 Advanced Interface Operation
The typical procedure for calibrating a Q-RPT in a PPC4-ui (with Advanced User
Interface) is:
Set-up and prepare the PPC4 for calibration (see Sections 7.2.2 and 7.2.3).
Activate the Q-RPT to be calibrated using [AutoRange], Range to choose the
Default Range of the Q-RPT (see Section 3.2.5). Be sure to set the DF
range (not an AutoRanged range).
Set the Head to zero using [Settings], <Pressure>, Head (see Section
3.2.16). Set the desired pressure unit of measure using [Settings],
<Pressure>, Pressure Unit (see Section 3.2.10). Set the desired pressure
measurement mode using [Settings], <Pressure>, Measurement Mode (see
Section 3.2.11). Axxx (absolute) Q-RPTs that will be used in gauge
measurement mode only, may be calibrated in gauge measurement mode
with a gauge pressure standard (see Section 7.2.5).
Check the AutoZ function using the AutoZ shortcut (see Section 3.2.22).
If calibrating in absolute measurement mode, turn AutoZ ON if it is left ON in
normal PPC4 operation. If calibrating in gauge measurement mode, always
turn AutoZ ON.
Use [Settings], <Calibration>, Hi RPT or Lo RPT , read and record the current
values of PA and PM for the Q-RPT to be calibrated. If calibrating in absolute mode,
also record the value of P
offset
from [Settings], <Calibration>, <AutoZ>,
Absolute Poffset ..
Run the recommended calibration point sequence for the Q-RPT (see Section
7.2.4) recording the pressure applied by the standard and the PPC4 reading at
each calibration point. Dwell at least 90 seconds at each point after setting the
reference pressure to allow full stabilization before taking data. The data recorded
is the “as received” data for this calibration.
Enter the calibration pressures and PPC4 readings into a spreadsheet. Calculate
the “non-corrected” PPC4 readings by backing out the PA, PM and P
offset
(P
offset
only in the case of Axxx (absolute) Q-RPTs in absolute mode) recorded in Step
above, following:
non-corrected reading = ((corrected reading - PA)/PM ) + P
offset
Perform a linear regression to find the offset and slope that best fit the non-
corrected PPC4 readings to the calibration standard pressures. The offset is
the new value of PA, the slope is the new value of PM.