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Date: Mon, 20 May 2013 22:44:54 -0400
From: Dave McGuire <mcguire AT neurotica DOT com>
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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] ITEAD?
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On 05/20/2013 10:08 PM, Stephen Ecob wrote:
>> Stephen Ecob wrote:
>>> one of the engineers of our "partner" company was very happy to
>>> explain how he'd modified it to give better linearity
>>
>> What were his modifications?
>>
>> Did he change some of your assumptions in order to accomplish the
>> better performance?
> 
> The PCA was an isolator for reading current shunts.  The 50mV peak
> shunt signal was boosted to about 5V and galvanically isolated.
> It was based on a linear optocoupler.  This optocoupler had a small
> but significant nonlinearity.  To obtain high accuracy we
> characterised this nonlinearity and cancelled it out in SW after the
> signal was digitised.

  !!

  Hey, feel like sharing that? :-)  (hey, the Chinese already have it!)

             -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA