PPCH-G™ OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company
Page 124
When running calibrations, collecting as received data and calculating PA and PM
adjustments, whether AutoZ is normally used, whether it is ON or OFF and what the value of
Zoffset is should be considered (see Section 3.5.1,
PRINCIPLE).
CalTool for RPTs software provided with the PPCH-G supports the calibration process of
PPCH-G Q-RPTs. CalTool and its documentation are provided on a General Accessories Disk with
the new PPCH-G. Most users should use CalTool software to assist in the calibration of PPCH-G.
PPCH-G is delivered with an interactive Q-RPT calibration utility that steps the operator
through the complete Q-RPT calibration procedure including applying the necessary
pressures, collecting data automatically, calculating new PA and PM values, previewing the
results of the new calibration and activating the results of the new calibration (see the
CalTool for RPTs manual on the General Accessories Disk). PPCH-G also provides
complete front panel and remote access to Q-RPT calibration parameters so that Q-RPT
calibrations can be performed without using CalTool software (see Section 5.2.8).
PPCH-G may also use external Q-RPTs mounted in RPM4 Reference Pressure Monitors.
RPM4 Q-RPTs are calibrated independently of PPCH-G (see the RPM4 Operation and Maintenance
Manual).
5.2.1.1
PA AND PM COEFFICIENTS
The coefficients used to adjust Q-RPT readings are designated PA (an adder or offset)
and PM (a multiplier or span set). The coefficients affect the Q-RPT reading
following:
Corrected reading = (uncorrected reading • PM) + PA
PA is expressed in units of pressure (always the SI unit, Pascal).
PM is dimensionless.
Each Q-RPT has its own unique PA and PM values. The PA and PM values
currently in use can be viewed and edited in the CAL function (see Section
5.2.7). PA and PM values are automatically edited when CalTool software is
used and the results are activated.
As editing PA and PM values will change Q-RPT calibration, they should only be
edited by qualified personnel as part of the calibration process. Caution should be
taken to avoid accidental editing and a security system is available to prevent access
(see Section 3.5.5.5). Incorrect editing of PA and PM values can cause out of
tolerance measurements.
A new PPCH-G is delivered with PA and PM values set to zero and 1 for all
ranges. This does not mean that the PPCH-G has not been calibrated. In the original
factory calibration, privileged factory coefficients are used for calibration with the
user PA and PM set to zero and 1.
