# [Kst] Zero calibration

Gunter Koenigsmann Gunter.Koenigsmann at semikron.com
Fri Feb 6 15:37:31 UTC 2015

```Dear all,

Sorry that I disturb you. But I found this exceedingly fast program
that seems to be capable to load any length of data and am now trying
for a long time already to do a seemingly simple thing -
that I am hoping to archieve with it:

I am measuring endless streams of positive and negative pulses that
look like the following:

0,0,1,1,0,0,1,1,0,0,1,1,0,0,-1,-1,0,0,-1,-1,0,0,-1,-1,0,0,-1,-1,0,0,1,1,0,0,...

The problem is that the measuring device only measures the AC part of
the signal. The result of the measurement actually doesn't look bad. But
a closer look shows that at the end of the sequence of positive pulses
the zero level has dropped a little below the actual zero line and ad
the end of the sequence of negative pulses the zero level has moved to a
place slightly above the zero line.

0,0.00,1,1,-.05,-.05,.95,.95,-.1,-.1,-.9,-.9,-.15,-.15,-1.1,-1.1,-.1,-.1,-1.05,-1.05,0,0,-.95,-.95,.05,.05,-.9,-.9,.1,.1,1.15,1.15,...

What I therefore need is a dynamical zero level correction. My plan was
to do something like the following:
1.) sample one pixel in every period the signal is near zero. The
frequency of the signal is rather stable so I just could take every nth
pixel and everything would be fine.
2.) connect these pixels by a line. Either a linear line, a spline or
whatever kst offers me.
3.) Subtract the resulting curve from the one I have measured and
declare the result to be the thing that actually happened.

I assumed that there would be a filter that samples only every nth
pixel or a login amp that samples only if the reference signal is below
a certain value or something similar. But I didn't find anything that
works.

Do you have any idea?
Alternatively is there a working link to a place that describes how to
write a plug-in? I would like to avoid having to write additional
software (and I don't have a working build system for windows but would
want to use my plug-in there, if even remotely possible) but would be
willing to, if that is really needed.

Kind regards,

Gunter.

Gunter Königsmann
R&D

Tel:     +49 911-6559-6025
Fax:    +49 911-6559-776747

www.semikron.com
gunter.koenigsmann at semikron.com

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