Micromeritics ASAP 2460, Operator'S Manual

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Appendix C ASAP 2460 Operator’s Manual
C-6 246-42800-01 - Aug 2013
Equilibration
Equilibration is reached when the pressure change per equilibration time interval (first derivative) is
less than 0.01% of the average pressure during the interval. Both the first derivative and average pres-
sure are calculated using the Savitzky-Golay
1
convolution method for polynomial functions. The
following equations are those used to compute weighted average and first derivative, respectively, for
the 6th point of an 11-point window.
where the numerical constants are from the Savitzky-Golay convolution arrays, and
P
avg
= average pressure
P
chg
= change in pressure
P
pcp,i
= percent change per interval
P
i
= i
th
pressure reading taken at equilibrium intervals
P
avg
36 P
11
P
1
+
 
– 9 P
10
P
2
+
 
44 P
9
P
3
+
 
69 P
8
P
4
+
 
84 P
7
P
5
+
 
89 P
6
 
+ + + + +
429
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
=
P
chg
5 P
11
P
1
–
 
4 P
10
P
2
–
 
3 P
9
P
3
–
 
2 P
8
P
4
–
 
P
7
P
5
–
 
+ + + +
110
---------------------------------------------------------------------------------------------------------------------------------------------------------------
=
P
pcp i

100%
P
chg
P
avg
----------
=
If a non-zero value that is too small is entered for the maximum equilibration time, the
points are collected before equilibration is reached.
If P
avg
is greater than 0.995 times the current Po, equilibration will not take place until
the Minimum equilibration delay for P/Po 0.995 has expired, in addition to the standard
equilibration criteria.