Equilibration - Micromeritics ASAP 2020 Confirm Operator's Manual

ASAP 2020 Confirm

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 pressure are calculated using the Savitzky-Golay
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.
– 36 P
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
P =
AVG

5 P
---------------------------------------------------------------------------------------------------------------------------------------------------------- -
P =
CHG
where the numerical constants are from the Savitzky-Golay convolution arrays, and
P
AVG
P
CHG
P
I
After equilibration has been reached, if the user-entered minimum equilibration time from the
Low Pressure Options dialog box has not elapsed, the equilibration continues until the entered
time has elapsed.
If the user entered a non-zero maximum equilibration time from the Low Pressure Options
dialog box, and this time period has elapsed before equilibration has been reached, the
equilibration ends as if equilibration had been reached, and the point is collected.
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
AVG
until the Minimum equilibration delay for P/Po 0.995 has expired, in addition to the
standard equilibration criteria.
1. Savitzky, A. and Golay, M.J.E., Anal. Chem. 36, 1627 (1964).
C-6
  
+ P + 9 P + P
11 1 10 2
  
– P + 4 P – P +
11 1 10 2
= average pressure (mmHg)
= change in pressure (mmHg)
th
= I pressure reading taken at equilibrium intervals (mmHg)
   
+ 44 P + P + 69 P
9 3 8
429
   
3 P – P + 2 P – P
9 3 8 4
110
Appendix C
1 convolution method
  
+ P + 84 P + P + 89 P
4 7 5
 
+ P – P
7 5
202-42811-01 - Mar 2011
 
6