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AD7779 for Load Cell application

Question asked by scaleguy on Dec 2, 2017
Latest reply on Dec 4, 2017 by Lluis

I am looking at using the AD7779, 8 channel, 24bit ADC for a load cell application.  My goal is to read up to 8 load cells simultaneously.  I only need an update rate of about 250 to 500 sps.  The load cells could be 2mV/V or 3mV/V, depending on the application.  I was planning on using an excitation voltage of 5V.  So that would put my max input at about 15mV (higher with a weight overload condition).

(As a side note I was planning on using the 12bit SAR to monitor the excitation to correct for any deviation in the Load cell supply.)


The internal PGA only goes to 8 so it seems like I would need to add an instrumentation amp on the front end of each channel.  Does someone have a recommendation for an IA?  I was thinking of using a gain of 100 on the external IA. I see there are only a few that have multiple amps per package I think I have the PCB real estate to handle individual IA's but few packages would be better.  


Any thoughts or suggestions would be appreciated.