DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
© 1998-2003 DH Instruments, Inc .
Page 70
Figure 40. DUT Definition Editor, [Correction] Tab
Table 17. DUT Definition Editor, [Correction] Tab Fields
FEATURE DESCRIPTION
Gas Density
Correction Type
(required drop
down list
selection)
Determines which type of density correction will be used when the DUT is run. The density
correction selected is applied to the reference flow to correct the reference flow to the
DUT’s normal operating conditions. The DUT flow is still determined by the output to flow
relationship setup on the
<Range> tab. Refer to the calculations in Section 19.5 for detail
on how the density correction is applied.
•
None - No density correction is applied. Entry in all other fields of this folder
is disabled. This is the normal selection for thermal mass flow controllers and meters
(MFCs, MFMs).
This should be the selection for any DUT for which it is not
explicitly known that a proportional or square root gas density correction is
appropriate.
•
Proportional - The ratio of the current gas density to the normal operating gas
density is used to determine the reference flow in the DUT’s normal
operating conditions. This type of correction is also used to determine actual or
volumetric flow. Turbine meters that output volume flow typically use this type
of correction. All fields in this tab require an entry when proportional is selected.
•
Square Root – The square root of the ratio of the current gas density to the normal
operating density is used to determine the reference flow in the DUT’s normal
operating conditions. Variable area style flow meters (rotameters) typically use this
type of correction. All fields on this tab require an entry when square root is selected.
Absolute
Pressure
(required numeric
entry if a gas
density correction
is used)
The normal operating pressure of the DUT. This value is provided by the DUT
manufacturer. It may be marked on the DUT and/or in its calibration report.
Enter the pressure value and select the pressure unit of measure. Note that the pressure
value is an
absolute pressure, not a gauge pressure. Gas density is a function of
absolute pressure. If the DUT normal operating pressure is specified as a gauge pressure,
add standard atmospheric pressure of 101.325 kPa (14.696 psi) to determine absolute
pressure. Refer to Section 19.5 for calculation details concerning this parameter.
If the DUT normal operating pressure is not specified at all, consider using standard
atmospheric pressure or the absolute operating pressure at which the DUT is typically
used if you know it.
Temperature
(required numeric
entry if a density
correction is used)
The normal operating temperature of the DUT. This value is provided by the DUT
manufacturer. It may be marked on the DUT and/or in its calibration report.
Enter the temperature and select the corresponding units of measure. Refer to
Section 19.5 for calculation details concerning this parameter.
If the DUT normal operating temperature is not specified at all, consider using 20 ºC or the
operating temperature at which the DUT is typically used if you know it.