Hoping I can get a bit of advise.....

I'm working on an interface as above, and I have a 3200:1 current transformer, trying to measure a maximum of 52A @ 230V AC. I want to convert the reading from the CT into a 0-5V reading suitable for input into a 16F877 PIC ADC, and unfortunately things are not working out.

Based on my calculations I have chosen a burden resistor of 307Ohm (V=IR/T..... 5=52*R/3200 therefore r=307ohm), giving 0.095V per amp out.

My problems are this:-

1. the voltage as measured across the burden resistor is an AC voltage, so therefore it will swing below 0, which will not suit the PIC.

I tried a bridge rectifier, but I suspect that the voltage drop across the diodes was screwing my readings at low I, as there might not even be 0.7V developed by the burden resistor until many amps of current were flowing through the CT primary.

I then read about of putting the rectifier before the burden resistor, with the theory that the rectifier will only rectify current, and then pass the current through the burden resistor to develop a proportional voltage - again (possibly due to my inability) this did not seem to work out too well.

2. I thought about a differential op-amp circuit, but am unsure how to construct same.

Has anybody any idea on how to accomplish this easily - I thought of an ade7753 chip but believe it is outside my progrmming ability on the PIC to sort out communications with it.

Also, even after the bridge rectifier I seemed to have an AC voltage across the resistor - am I assuming correctly that this is due to insufficient smoothing after the rectifier?

Any ideas on how to work around this would be greatly appreciated.

Kind regards,

GG339