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Load Cell ADC Parts Decision Help

Question asked by failsafe on Sep 12, 2011
Latest reply on Sep 13, 2011 by failsafe

Hello,

         I need to convert the analog signal of a load cell.  I want to use a 16-Bit Single channel ADC with SPI for that purpose.  The reason for the 16 bits is that I currently have other ADCs (single ended potentiometers) on the SPI bus.  After they are converted to digital, everything gets packaged together and sent off using rs-485.  Also, the existing code expects 16 bit values for everything.

 

The AD7715 looks like a fantastic part but its too slow.  Because I have to package all of the converted values I would end up waiting for the load cell or transmitting an old value with the rest of the ADCs.  Therefore it looks like I need to go to an SAR.  I am having trouble picking a good SAR + Differential ADC Amplifier combination.

 

Couple of things:

 

Load Cell is 2mV/V for excitaion.  Its currently wired up with 10V but if I could use 5V it would really simplify my design.  So max output is either 10mV or 20mV depending on whats practical for the input of an ADC amplifier.

 

The SPI bus is 3.3V.

 

The speed doesnt need to be incredibly fast 250-500K is plenty, over 1Mbps would be great.  10Mbps is overkill.

 

I was hoping someone could give me some suggestions on what they have used or what might fit my needs.  I have used parametric search but have been going in circles a bit.

 

Thanks,

Karl

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