Thanks for your response David.
My application requires a full scale current measurement of only 10 Arms and I am using a CR Magnetics CR8448 CT that has a ratio of 1:2510. When you do the math, the 10Arms will give 1.1 Vpp with the 100 ohm load, which is the upper limit as it should be. 100 ohms was the value used in the Dev Board manual.
Where did you see that the PGA gains should always be = 1 when using a CT to drive them?
I assumed that the " Zxxx interrupts" error was caused by the signal being too low - the manual said the zero crossing detection stops of the signal is less than 10% of full scale and I couldn't find a way to turn this off. If any thing I would be making the burden resistors bigger to get more signal
I chose the 7880 because from the data sheet it had the ability to have a high accuracy over a large dynamic range which is what my application needed. My test load of 2 amps was chosen just because that was something I had around and I thought it would be ok given the large dynamic range of the chip. I spent a whole day reading the data sheet and Dev board manual and could find no explanation for the errors I got and the fact that I couldn't set the PGA gains using the Dev board SW or even check what they were set at stopped me. The only work around I could see was to use my own microcontroller to drive the 7880 so that I could set and read all the registers to make sure they actually go set.
Regards,
Bruce