Micromeritics TriStar II 3020 Operator's Manual page 312

Appendix C
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
equations below are those used to compute weighted average and first derivative, respectively, for the
6th point of an 11-point window.

– 36 P
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
=
P
AVG

5 P
--------------------------------------------------------------------------------------------------------------------------------------------------------------- -
=
P
CHG
= 100%
P
PCPI
where the numerical constants are from the Savitzky-Golay convolution arrays, and
P =
AVG
P =
CHG
P =
PCPI
P =
I
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 is greater than 0.995 times the current Po, equilibration will not take place until
AVG
the Minimum equilibration delay for P/Po 0.995 has expired, in addition to the standard
equilibration criteria.
C-4
1
  
+ + 9 P + + 44 P
P P
11 1 10 2
   
– + 4 P – + 3 P
P P
11 1 10 2 9
110
P
CHG
------------- -
P
AVG
average pressure (mmHg)
change in pressure (mmHg)
percent change per interval
th
I pressure reading taken at equilibrium intervals (mmHg)
convolution method for polynomial functions. The
   
+ + 69 P + + 84 P
P P
9 3 8 4
429
   
– + 2 P – + –
P P P P
3 8 4 7
TriStar II 3020
   
+ + 89 P
P
7 5 6

5
302-42828-01 - Dec 2012