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AD7147 capacitance resolution confusion

Question asked by tommytech on Mar 28, 2013
Latest reply on Apr 2, 2013 by tommytech

Earlier in this forum, the AD7147 resolution was given as 24.4fF per count or about 1600 pf for a full scale 16 bit output.

Figure 18 in the data sheet shows roughly 60,000 counts for a 25 pF Cx or about 0.4 fF per count.

The specified input Cx range in the table is +/- 8 pF for a resolution of about 0.25 fF per count.

 

I'm having trouble reconciling all of the above. My application involves measuring the delta-C in approximately calibrated units (large scale offsets are not important).

 

Can someone clear this up for me?

 

Thanks,

 

tommy

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