DH Instruments PPCH, Руководство по эксплуатации и обслуживанию

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3. OPERATION
Page 41 © 2009 DH Instruments, a Fluke Company
Internally, PPCH 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 pressure unit of measure for the active
range, press
[UNIT]
from the MAIN RUN screen while
the range is active. The display is:
1MPa 2kPa 3hPa
4bar 5mbar 6psi
The cursor is on the number corresponding to the pressure unit of measure active for the current 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 measurement unit 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 active range unit of measure.
See Section 7.2.1 for tables of the
conversion
factors used by PPCH.
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 PPCH 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 3.5.4.2).
3.3.3 [MODE]
 PURPOSE
To set the measurement mode (absolute or gauge) for the active range.
For information on selecting the unit of measure, see Section 3.3.2.
 PRINCIPLE
PPCH supports simple, one-step switching between two measurement modes:
Absolute
Measures pressure relative to vacuum (zero is hard vacuum). Range is
from zero absolute to full scale. Minimum set pressure is atmospheric
pressure (vented).