## PSN-L Email List Message

Subject: Re: WinSDR screen calibration
From: Larry Cochrane lcochrane@..............
Date: Mon, 21 Dec 2009 18:29:16 -0800

```Hi Brett,

I think you mean A/D not D/A, WinSDR does not deal with D/A converters. Also, I think
you mean X-Scale not Y-Scale. The Y-Scale controls the signal level (up/down motion)
in the real-time window or GIF image and the X-Scale controls the time. The number of
lines per channel and the time period per line has nothing to do with the Y-Scale. If
you mean the X-Scale, the X-Scale is in minutes per line.

Regards,
Larry Cochrane
Redwood City, PSN

Brett Nordgren wrote:
> 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
> setting.
>
> 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
> line.
>
> 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?
>
> Regards,
> Brett
>
> Watch our wiggles
> http://bnordgren.org/seismo/gif_images.htm
>
> or watch some very very good wiggles
> http://aslwww.cr.usgs.gov/Seismic_Data/telemetry_data/ANMO_24hr.html
>
>
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