Micromeritics TriStar II 3020 - Page 312

Appendix C TriStar II 3020
C-4 302-42828-01 - Dec 2012
Equilibration
P
AVG
36 P
11
P
1
+–9P
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
PCPI
100%
P
CHG
P
AVG
--------------
=
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
equations below 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 Sa
vitzky-Golay convolution arrays, and
P
AV G
= average pressure (mmHg)
P
CHG
= change in pressure (mmHg)
P
PCPI
= percent change per interval
P
I
=I
th
pressure reading taken at equilibrium intervals (mmHg)
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.