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CN0540 + CN0532 LSB to g conversion

Thread Summary

The user asked why 1 g measured by the ADXL1002 in the CN0532 setup corresponds to 63200 LSB at the output of the AD7768-1 in the CN0540, instead of the expected 81920 LSB. The final answer explained that the CN0540 has a total gain of 0.8 from sensor to ADC, which reduces the expected output. The accompanying answer clarified that this gain is derived from the level shifter inverting gain (0.3) and the FDA gain (2.67) as detailed in the CN0540 document.
AI Generated Content
Category: Hardware

Hi, according to the AD7768-1 datasheet (with a 4.096 V reference as is the case in CN0540) 1 LSB size is equal to 488.28 nV.

Also, according to the CN0532 and ADXL1002 datasheet, this sensor produces 40 mV/g.
 
That would mean that 81920 LSB at the output of AD7768-1 equals 1 g measured by the CN0532, assuming that 1 V at the output signal of CN0532 is equal to 1 V at the input of AD7768-1. 
But when using CN0540 + CN0532, I roughly measure that 1 g equals 63200 LSB (I've checked by fixing the accelerometer positive axis downward, flat and upward).
I'm using the CN0540 (AD7768-1) default settings.
Could somebody please explain to me the reason for that difference? I'm missing something in the middle between CN0530 and CN0540 when making that calculation?
Regards,

Edit Notes

Typing error modified
[edited by: FelipeCook at 1:29 PM (GMT -5) on 17 Nov 2023]

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