PPCH-G™ OPERATION AND MAINTENANCE MANUAL
© 2007 DH Instruments, a Fluke Company
Page 36
See
Section
7.2.1 for tables of the
conversion
factors used by PPCH-G.
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-G 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 set 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-G 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).
Gauge
Measures pressure relative to atmosphere (zero is ambient pressure)
using PPCH-G’s automated offsetting of atmospheric pressure with
dynamic compensation for atmospheric pressure changes (see Section
3.2.4). Range is from zero gauge to full scale.
The maximum pressure of each Q-RPT is the same in absolute and gauge measurement
modes.
If the Q-RPT will not be used in absolute mode, absolute mode can be turned off to avoid
using it unintentionally (see Section 5.2.5).
OPERATION
To change the active measurement mode for a range,
press
[MODE]
from the MAIN RUN screen while the
range is active. The display is:
Measurement mode:
1abs 2gage
Only gauge mode is available if absolute mode is OFF (see Section 5.2.5).
Certain PPCH-G settings, including AutoZ ON/OFF (see Section 3.5.1) are range AND
measurement mode specific. See Table 5 for a listing of settings and what they are specific to.
