DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
Page 71
© 1998-2003 DH Instruments, Inc .
FEATURE DESCRIPTION
Process Gas and
Gas Constant
(required entry if a
density correction
is used)
The currently selected <Process Gas> is the process gas specified in the <Header> tab
(see Section 8.5.2) and cannot be changed here. The gas constant in this panel must
correspond to the process gas. The drop down list should be used to determine how the
gas constant information is entered. In the event the
<Process Gas> is also a
COMPASS supported <Calibration Gas> , all gas specific entries are disabled, and
COMPASS will automatically calculate the gas density based on the pressure and
temperature data entered. The choices are:
•
Molecular Mass (g/mol) – The entry field should contain the molecular mass in
g/mol units. COMPASS automatically enters this value when the process gas is also
a supported calibration gas.
•
Specific Gravity – The entry field should contain the dimensionless specific gravity
value for the process gas. This value is the ratio of the gas density in standard
conditions to the density of air in standard conditions.
•
Density (kg/m³) – The entry field should contain the density of the gas in the
specified normal operating pressure and temperature conditions. COMPASS will not
modify this value when applying the density correction. In the previous cases,
COMPASS must calculate the density using the entered information prior to applying
the density correction.
Refer to Section 19.5 for calculation details concerning this parameter.
In all cases, make absolutely sure that the gas constant value entered is in the proper
units and corresponds to the current <Process Gas>. Failure to due so will result in
erroneous data.
Process Gas
Compressibility
(required entry
if a density
correction
is used)
Specifies the compressibility factor of the <Process Gas> at the DUT’s normal operating
conditions (listed in the <Normal Operating Conditions> panel of this tab. The gas
compressibility does not change significantly over a very wide range of pressure and
temperature. For this reason, 1.00 is used as the default value. This entry is used to determine
the density of the
<Process Gas> in the DUT’s normal operating conditions. Refer to
Section 19.5 for calculation details concerning this parameter. When the gas constant is entered as
a density value, this field is disabled.
8.5.4 [RANGE] TAB
The DUT Definition [Range] tab is provided to define the relationship between the DUT flow,
output and set point (if applicable) ranges and units. It is assumed that all of these values are
linearly proportional in the sense there is a constant ratio between output, flow and set point.
Select the units that correspond to each parameter using the drop down list provided.
Table 18 provides details on each of the [Range] tab fields.
Figure 41. DUT Definition Editor, [Range] Tab