5. MAINTENANCE, ADJUSTMENTS AND CALIBRATIONS
Page 95
© 2008 DH Instruments, a Fluke Company
RPM4-E-DWT is delivered with an interactive Q-RPT calibration utility (CalTool for RPTs) 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 E-DWT-10000-AF Support Disk). The
RPM4-E-DWT 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 5.3.7).
CalTool for RPTs software supports the calibration process of RPM4-E-DWT Q-RPTs.
CalTool and its documentation are provided on the E-DWT-10000-AF Support Disk which is
delivered with a new E-DWT-10000-AF. CalTool for RPTs can also be downloaded from
www.dhinstruments.com. The use of CalTool software to assist in the calibration of RPM4-E-DWT is
highly recommended.
5.3.1.1
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.
Since the RPM4-E-DWT operates in gauge mode only and the Q-RPT is zeroed
at the time of calibration and frequently rezeroed during calibration, PA should
not be significantly different from zero.
Each Q-RPT has its own unique PA and PM values. The PA and PM values
currently in use can be viewed and edited from the front panel in the CAL
function (see Section 5.3.6). PA and PM values are automatically edited when
CalTool software results are activated.
As editing PA and PM values changes 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 3.9.5.5). Incorrect editing of PA and PM values can cause out of
tolerance measurements.
A new RPM4-E-DWT is delivered with PA and PM values set to zero and 1 for all
Q-RPTs. This does not mean that the RPM4-E-DWT 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.
5.3.2
EQUIPMENT REQUIRED
The recommended calibration standard for the RPM4-E-DWT A70M/A7M-AF Q-RPTs is a
DHI PG7302 piston gauge. Contact DHI for additional information.
