Hi
I read a metering application note:Implementation of a Single-PhaseElectronicWatt-HourMeter Using the MSP430AFE (slaa494a) and I have a doubt in the current measurement section.
There are two modes of ADC:single and differential.
Single uses one input and compares it with anyone of VREF+ or VRef- or ground.Differential uses two inputs and converts the differential voltage to digital value.
Figure 2 of the document displays the simplistic schematic of energy meter.Two Channels are there.Line current channel uses CT and Neutral current Channel uses Shunt and the signals are going to differential ADC
Why I1- is connected to Neutral(which is considered as ground for the design)?
V1- is connected to neutral and in Neutral current channel ,I2- is connected to one end of shunt which is neutral,so no doubt here.
But,In Line Channel ,CT is used,which means Primary and Secondary are isolated.
So,depending upon the current in the primary,a voltage is formed across secondary based on value of burden resistor (this voltage is measured by ADC)
But is it connected to neutral.I don't understand why it has to be connected to ground.
Waiting for your reply.
Regards,
Deebanmadhu H,
L&T - MPS,Mysore.
