DH Instruments PPCH, Руководство по эксплуатации и обслуживанию

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5. MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 143 © 2009 DH Instruments, a Fluke Company
5.3.8 Q-RPT CALIBRATION/ADJUSTMENT WITHOUT CALTOOL
FOR RPTS SOFTWARE
 PRINCIPLE
The PPCH Q-RPTs can be calibrated and adjusted without using CalTool for RPTs software.
This requires:
•
Applying pressures with a calibration standard and recording the pressures measured by
PPCH.
•
Calculating new PA and PM values and entering them.
•
Setting P
offset
to zero for Q-RPTs that will be used in absolute mode.
Before proceeding to calibrate a reference pressure transducer without using CalTool for RPTs
software, Sections 5.3.1, 5.3.2 and 5.3.3 should be reviewed thoroughly.
 OPERATION
The typical procedure for calibrating a Q-RPT is:
Set-up and prepare the PPCH for calibration (see Sections 5.3.2, 5.3.3).
Use the
[RPT]
function key to select the Q-RPT to be calibrated (see Section 3.3.5). Be
sure to set the DF range (not an AutoRanged range).
Use
[HEAD]
to set the HEAD to zero (see Section 3.3.7). Use
[UNIT]
to set the desired
pressure unit of measure (see Section 3.3.2). Use
[MODE]
to set the desired pressure
measurement mode (see Section 3.3.3). PPCH 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 5.3.5).
Use
[SPECIAL]
,
<1AutoZ>
to access the AutoZ function (see Section 3.5.1).
If calibrating in absolute measurement mode, turn AutoZ ON if it is left ON in normal
PPCH operation. If calibrating in gauge measurement mode, always turn AutoZ ON.
Use
[SPECIAL]
,
<8cal>
,
<1Hi RPT>
or
<2Lo RPT>
,
<1view>
, to 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, abs
.
Run the recommended calibration point sequence for the Q-RPT (see Section 5.3.4)
recording the pressure applied by the standard and the PPCH reading at each calibration
point. The data recorded is the “as received” data for this calibration.
Enter the calibration pressures and PPCH readings into a spreadsheet. Calculate the
“non-corrected” PPCH readings by backing out the PA, PM and P
offset, abs
(P
offset, abs
is
necessary only if the Q-RPT is being calibrated in absolute mode) recorded in Steps and
above, following:
non-corrected reading = ((corrected reading - PA)/PM ) + P
offset, abs
Perform a linear regression to find the offset and slope that best fit the non-corrected
PPCH readings to the calibration standard pressures. The offset is the new value of PA,
the slope is the new value of PM.
Press
[SPECIAL]
,
<8Cal>
,
<1Q-RPT>
,
<2edit>
and write 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 mode OFF so that it cannot be
used after the calibration.