DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
Page 191
© 1998-2003 DH Instruments, Inc .
19.6 TOLERANCE
The determination of whether a point is in or out of tolerance depends on the type of tolerance selected,
and the DUT and reference flows. Tolerance values may be specified in multiple units (see
Section 8.5.5).
COMPASS first determines the tolerance value in DUT flow units and then compares the
value to the current DUT flow error to determine if the error is smaller (in) or larger (out) than
the tolerance. When the DUT tolerance selection is (%D %Reading) the tolerance is the sum of
the two values. If the selection is %DUTspan or %Reading, the tolerance used is the greater of the two
values. Tolerances that are defined in DUT flow, set, or output units are also compared directly in flow
units. The conversion from set and output units is described in Section 19.3.
DUTspan
DUTspan
DUTspan
Q
T
QT
× =
100
%
%
QT
T
Q
reading
reading
f %
%
Re
= ×
100
VARIABLE DESCRIPTION
T
DUTspan %
%DUTFS tolerance value defined in the DUT definition.
Q
DUTspan
DUT flow range span as determined by the difference between the
maximum and minimum flow output values in the DUT Definition.
DUTspan
QT
%
Maximum allowable( DUT – reference flow) deviation based on a
%DUTFS tolerance.
Q
f Re
Current reference flow.
T
reading %
%Reading tolerance value defined in the DUT definition.
QT
reading %
Maximum allowable (DUT – reference flow) deviation based on a
%Reading tolerance.