DH Instruments E-DWT-10000-AF, Руководство по эксплуатации и обслуживанию

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E-DWT-10000-AF OPERATION AND MAINTENANCE MANUAL
© 2008 DH Instruments, a Fluke Company Page 94
5.2.2 ADJUSTMENT OF THE ON-BOARD BAROMETER
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PURPOSE
To adjust the output of the on-board barometer (see Section 3.9.7.1).
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PRINCIPLE
The on-board barometer output can be adjusted using PA and PM values following the same
principles as for the Q-RPTs (see Section 5.3.1.1).
Since the on-board barometer is not a source of traceable pressure values, it does not have
to be formally calibrated. It should be offset to agree with a reference barometer. To offset
the barometer, change the barometer pressure adder (PA).
The on-board barometer is used only for measuring changes in atmospheric pressure over
short periods of time (see Section 3.9.1). RPM4-E-DWT measurement uncertainty does NOT
depend on the absolute accuracy of the on-board barometer.
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OPERATION
To view or edit the values of PA and PM for RPM4-E-DWT’s on-board barometer, press
[SPECIAL] , <8cal> , <3barometer> . Pressing [ENT] steps through displays of the calibration
date [YYYYMMDD] and PA and PM. In edit mode, the values can be edited. Pressing
[ENT] after the last screen activates the edited values.
To view the current output of the on-board barometer, press [SPECIAL], <7intern>, <3baro>
from the main run screen.
A pressure standard may be connected to the on-board barometer by connecting to one of
the ATM ports on the RPM4-E-DWT rear panel Q-RPT modules (10-32 UNF). The operating span of
the barometer is 10 psi (70 kPa) to 16 psi (110 kPa).
Never apply a pressure greater than 16 psi (110 kPa) to the barometer port. Overpressure
and possible damage may result.
5.3 RPM4-E-DWT Q-RPT CALIBRATION
5.3.1 PRINCIPLE
RPM4-E-DWT A70M/A7M-AF has two quartz reference pressure transducers (Q-RPTs) that
are the source of low pressure measurement uncertainty for the system.
To adjust a Q-RPT, pressures from a reference standard are applied to the Q-RPT at
ascending and descending pressure increments over the range. The pressure defined by the
standard and the corresponding Q-RPT readings are recorded at each point. After all of the
pressures have been applied and recorded, adjustments are made to fit the Q-RPT pressure
readings to the standard. Fitting the readings means performing a least squares linear
regression to arrive at the lowest value of the residuals of errors of the Q-RPT relative to the
standard. The Q-RPT output is adjusted by user settable coefficients: PA (an adder or offset)
and PM (a multiplier or span set) (see Section 5.3.1.1).
The calibration process is performed independently on each Q-RPT to arrive at its optimal fit.