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i found in many weight scale reference designs that they use either low noise linear regulator or voltage reference for voltage stabilization.

Why do we use them if ratiometric design cancel the change of adc output caused by excitation voltage change?

Can i connect ratiometric weight-scale system to 3.7 V Lipo battery without any stabilizer and be sure that results wouldn't be affected by battery voltage drop due to discharging?

Many thanks, Matija

Ratiometric design

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    \$\begingroup\$ The bridge output voltage is proportional to the supply voltage. Do the maths. \$\endgroup\$ – Chu Aug 3 '17 at 23:33
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    \$\begingroup\$ @Chu - Yeah, but so is the ADC reference. The two ought to cancel. \$\endgroup\$ – WhatRoughBeast Aug 4 '17 at 1:01
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    \$\begingroup\$ Yes, but ADC voltage resolution is also proportional to supply voltage (reference). analog.com/en/analog-dialogue/articles/… "The bridge output is directly proportional to the excitation voltage, and any drift in the excitation voltage produces a corresponding drift in the output voltage. By using a voltage that is proportional to the bridge excitation voltage as the ADC’s reference source, there is no loss in measurement accuracy if the actual bridge excitation voltage varies. This ratiometric connection removes the effect of drifts..." \$\endgroup\$ – fender_cro Aug 4 '17 at 1:03
  • \$\begingroup\$ Yes, didn't spot that. \$\endgroup\$ – Chu Aug 4 '17 at 6:58
  • \$\begingroup\$ Your block diagram doesn't show delay through LPF, and delay taking ADC reading. Any supply changes (noise) during delays would cause error. \$\endgroup\$ – glen_geek Aug 4 '17 at 11:03

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