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Subject: WinSDR screen calibration
From: Brett Nordgren brett3nt@.............
Date: Mon, 21 Dec 2009 09:38:48 -0500

Hi all,

I had recently been working with calculating the per-line scale factor for 
some GIF's
being produced by WinSDR, so I took the opportunity to try to characterize 
how that
generally relates to the number of lines displayed and the Y scale factor 

So far what I have observed seems to suggest:

Given that
n is the number of lines displayed
Y is the WinSDR Y scale factor

For my screen (and possibly for any screen),
D/A counts per line = 913 / (n+1) * Y
So for a 24 hour - 24 line screen with Y = 2:
counts per line = 913 / 25 * 2 = 73.04

If you are using a 16-bit, +-10V D/A you can go on to calculate:

Volts per line = 73.04 counts/line / 3276.8 counts/Volt = 0.0223

The constant 3276.8 is 32,768 counts / 10 V, the maximum values
for a 16-bit +-10V D/A

And finally, from that, if you know your instrument's Volts / unit of 
ground motion,
you can divide by that number to get the ground motion represented by each 

This seems to hold true for both the screen displays as well as for GIF 
file creation.

Larry, I'd be interested in whether this seems to make sense to you, and have
I missed anything?


Watch our wiggles

or watch some very very good wiggles


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