Dear Dayama,

This is an old thread and I have already designed and delivered the product. It has been tested by ERTL Kolkata.It is due for testing at NABL Hyderabad and has been approved by GE Bangalore.

1. I am aware of the diode loss and when use a transformer for isolation, I make sure of the following.
a. The transformer never saturates.
b. The sensing winding is sufficiently higher (at least 10x) than the measuring span.
c. Use Schottky diode (0.135 volts Fwd) or active rectifier (OP-Amp based)
d. Use a slope routine to nullify any non-linearity.
e. Do averaging of ADC routines.

Cost constraints do not allow me to use a rms converter chip from LT or AD.

For my typical measuring requirement it is a naval ship and you don't have a neutral there!!!!!!!

When cost permits I use the IL300 linear opto from Vishay or Siemens. I have my owm PIC (12Fxxx) that works as a voltage to serial converter (opto-interface) powered by non-dissipative capacitive power supply.

Low cost is important but I need to optimize my design around the thin line.

Regards

Sougata