I have been trying to calibrate the 7758 and then read energy, voltage and current values. I have several problems, so I will start with the most basic.
I seem to be missing some piece of information on how to convert the register values into real-world watts. My understanding is that you simply compute a Wh/LSB constant from your design, read the WATTHR register, multiply by the register value by the constant and convert from kW to W.
If I do the Wh/LSB computation, I get ~.0002820
Applying 7 amps at 166.6 volts to the circuit, I read 7956d from the WATTHR register after 5 seconds of accumulation. This is a resistive circuit (PF=1), so the result should be basically V * I. 116.6 * 7 = 816.2W.
I do not see how to use the constant to get the correct result. My guess is that there is some factor involving accumulation time that I am not taking into account. I did use 5 seconds as the time when computing the Wh/LSB constant.
What am I missing? Can someone explain how to get the correct watt value based on the above numbers?