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3. OPERATION
Page 27 © 2004-2007 DH Instruments, a Fluke Company
Internally, RPM4 always operates in Pascal (Pa), the SI unit of pressure. Values of pressure
are represented in other units by the application of conversion factors to convert from Pa
(see Section 7.2.1).
OPERATION
To change the active pressure unit of measure for a
range, press [UNIT] from the MAIN RUN screen while
the range is active. The display is:
1kPa 2Pa 3MPa
4hPa 5bar 6mbar
The cursor is on the number corresponding to the active pressure unit of measure for the active range.
To change the pressure unit of measure, select the desired unit. Making the selection
returns to the MAIN RUN screen with the selected unit active.
The pressure unit of measure selected is range specific. When in a given range, all functions
and settings are represented in the current measurement unit for that range. However,
certain internal and/or metrological functions (e.g., Q-RPT calibration coefficients) are always
represented in Pa regardless of the current range unit. When the current unit is an altitude
unit, the range and upper limit indications are in kPa if the unit is meters (m) and psi if
the unit is feet (ft).
See Section 7.2.1 for tables of the conversion factors used by RPM4.
If the pressure unit selected is inWa (inches of water), the reference temperature for water
density must we specified in a separate menu (choices are 4ºC, 20ºC 60ºF). No reference
temperature selection is necessary for the unit mmWa as the only reference temperature
commonly used for mmWa is 4 ºC.
The default pressure units of measure available under the UNIT function depend on whether
the RPM4 has been set up as an SI or US version (indicated by SI or US at bottom right of
introduction screen). The choice of six units available under the UNIT function can be
customized from a wider selection by the user (see Section 3.5.6). The units available under
the UNIT function can be reset to default by reset (see Section 3.5.9.2).
3.3.3 [MODE]
PURPOSE
To set the measurement mode (absolute, gauge, negative gauge or differential) for the active range.
For information on selecting the unit of measure, see Section 3.3.2.
PRINCIPLE
RPM4 supports simple, one-step switching between up to four different measurement modes:
Absolute Measures pressure relative to vacuum (zero is hard vacuum). Range is
from zero absolute to full scale.