Hi Dan,
 
I changed the op amp last week and it is now working. Thanks for your response as well. I was measuring the 0.8V with a DMM at the input to the ADC.  But now with the new op amp it is working.
 
Ben


From: Dan Nelson [mailto:Dan.Nelson@romteck.com]
Sent: Monday, 28 May 2012 12:15 PM
To: General mailing list for gumstix users.; Keane, Ben (STRX)
Subject: RE: [Gumstix-users] ADC characteristics

Sounds like your voltage follower doesn’t have enough grunt to drive the ADC.  Where are you measuring the 0.8 volts?  At the input to the buffer or at its output?

Dan

 

From: Keane, Ben (STRX) [mailto:ben.keane@kaelus.com]
Sent: Tuesday, May 22, 2012 2:31 PM
To: General mailing list for gumstix users.
Subject: [Gumstix-users] ADC characteristics

 

Hello Mailing List,

 

I am wondering if anyone has characterized the ADC's on the gumstix?  I am experiencing a non-linear response... depending on the buffers (on a custom board) output resistance, the characteristic changes. It seems that until the ADC value reaches 0.8V with a measured current draw of 0.24mA the ADC will just measure 0... After that point, it will start to measure linearly.  When driven directly from the power supply the voltage response is linear, but when diven from an voltage follower, it is not.

 

Any help would be much appreciated.

 

Many Thanks,

 

Ben

 

 

 

 

 

 

 

 

 

 


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