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Re: [ts-7000] Re: accessing extra ADC on 7250

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Subject: Re: [ts-7000] Re: accessing extra ADC on 7250
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Date: Wed, 25 Jul 2007 01:56:32 -0400
>No, that's the graph I'm referring to.  It's a straight line, but look
>at the digial values: they are not monotonic.  
>
>If you replot it as described above you'll see two sections: one has
>xrange (0:61A8) and yrange (vref/2:vref), the second has xrange
>(9E58:FFFF) and yrange (0:vref).  I'd try ascii art, but I know better :)

It looks monotonic to me.

The thing to notice is that this graph shows that the output is signed.
Zero counts is at vref/2.  Voltages less than vref/2 are negative counts
and voltages greater than vref/2 are positive counts.

Or, to put it another way, -25000 is the lowest voltage (zero) and
+25000 is the highest voltage (vref).  (more or less - the graph
shows that those limits are approximate.  i.e. don't be shocked if
you see +25001.)

The easiest way to deal with this is to sign extend the value when you
pick it out of the ADC, then use ordinary scaling after that.

Mark S.


 
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