3.1.1 AC Voltage Measurement Using Differential ADC
Figure 3-2. AC Voltage Measurement Using
Differential ADC
AC voltage to be measured is fed as
input to the AC voltage step-down circuit made up of an isolation transformer
The step-down AC voltage is filtered
using OPA
An offset voltage is added to shift
the step-down AC voltage using DAC, and it is made compatible with the ADC
measurement range
Then the OPA output is fed to the ADC
positive channel, and the added reference offset voltage is given as input to the
negative channel of differential ADCC
Differential ADC removes the common
mode noise and the effects of adding of the offset voltage. During RMS calculation,
offset need not be added by the software as the Differential mode already has
removed the effect
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