Warning !

Soas is no longer maintained. You are strongly encouraged to switch to its successor, QSoas


(film_decay) Correct for film loss when the activity is a step function

(from version 3.6.5) To correct a chronoamperogram that is s step function distorted by film loss, according to the method in ref [2] load it and run the film_decay command. The terminal goes...

INFO: currently  1 partitions
 Partition data
 (f): fixed size division
 (j): jump-based estimation
 (s): save partition
 (l): load previously saved partition
 (q): cancel
 (y,o,mid): accept
... as SOAS is trying to identify the different intervals.

Choose f if the data whose film decay you wish to correct consists of intervals that have the same size.

Else, type j, for the typical case where steps are of random size, but well separated by a ``jump'' in current. After you type j, the terminal says:

INFO: Starting auto partitioning
INFO: currently  4 partitions
 Auto-partition data
 (q,o,y, mid) to accept
 Jump partition parameters
(i) minimum interval size: 50
(a) averaging over 10 elements
(j) jump factor:    2.000
(m) minimum delta:   0.2300E-07

Soas uses a rather crude algorithm to detect those jumps: it will detect a new interval only i points (default is i=50) after the previous one, if the value of the difference between two consecutive points is larger than the minimum delta (parameter m) and at least j times (default j=2) larger than the average difference over the last a elements (default a=10). Of course the four parameters can be set to different values.

This screen capture illustrates the result:

It is strongly advised to remove spikes on the data before using the ``jump-based partitioning'' scheme.

Accept the partition by typing q, or o, or y or by clicking the middle button of the mouse; you are back to the previous prompt.

After the particion is accepted, the terminal says:

INFO: currently 4 partitions
 Partition data
 (f): fixed size division
 (j): jump-based estimation
 (s): save partition
 (l): load previously saved partition
 (q): cancel
 (y,o,mid): accept
It is possible to save the current partition and reload it from a file using s and l. The partition is saved as (and read from) a plain text files containing the 1-based index of the first data point of each interval.

Once the partition is satisfactory, type o, y or click on the middle button to proceed to the film decay estimation. q at this point cancels the process.

Next, each interval is successively displayed full scale; for each interval, a text message is displayed to tell you what's on:

Film loss estimation on interval   46.80     ->    91.80    ( 2/ 4)
 (0, mid) : no film loss
 (k) : enter manually k
 (l) : linear regression estimation

If you think that film loss is negligible on this interval, type 0 or click the middle button. Else, typing l lets you select the X-range that is used for fitting the data to a straight line (like with the reg command) and measuring the time constant of the decay for the entire interval.



After all intervals have been examined, SOAS exits the command replacing the buffer with the normalized time-dependent coverage. Use the div command to divide the raw chronoamperometric data by this coverage to correct the signal for film loss.

Warning !

Soas is no longer maintained. You are strongly encouraged to switch to its successor, QSoas
Christophe Leger 2009-02-24