DH Instruments COMPASS FOR MOLBOX, Руководство пользователя

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COMPASS

for molbox™ User’s Manual
Page 189
© 1998-2003 DH Instruments, Inc .
%Reading errors are undefined near 0 (zero) reference flows.
Set point errors are determined using the measured DUT set point whenever possible. If a measured
value is not available, the nominal value is used as the set point.
E
Q Q
Q
DUTFS
DUT f
DUTspan
%
Re =
−
×
100
E
Q Q
Q
Rdg
DUT f
f
%
Re
Re
=
−
×
100
100
_ %
×
−
=
DUTspan
Set ref
Set DUTFS
Q
Q Q
E
100
_ %
×
−
=
set
set ref
Set Rdg
Q
Q Q
E
VARIABLE DESCRIPTION
Q
DUT
Current DUT flow.
Q
f Re
Current reference flow.
Q
DUTspan
DUT flow range span as determined by the difference between the
maximum and minimum flow output values in the DUT Definition.
E
DUTFS %
DUT percent of full scale error.
E
Rdg %
DUT percent of reading error.
Q
Se
DUT set point flow in DUT flow units.
Set DUTFS
E
_ %
DUT percent of full scale set point error.
Set Rdg
E
_ %
DUT percent of reading set point error.
19.5 DENSITY CORRECTIONS
COMPASS includes two gas density correction options to assist in testing of gas density dependent
devices under conditions different from their normal operating pressure and temperature conditions. The two
correction types are square root and proportional.
The gas density correction consider only gas density and no other pressure or temperature based DUT
corrections. For example, gas viscosity changes with pressure and temperature and this can have a
significant effect on small float rotameters but
COMPASS does make a viscosity correction. Gravity has
an effect on rotameters but COMPASS has no gravity correction. Generally, corrections other than
density are not significant relative to the tolerances of these types of devices but, since they will not be