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I have not looked at your code yet, but I doubt there is a non-linearity in the code. It is more likely to be a hardware and construction issue. What values do you see on the serial output from your emonTx? If they are the same as the GLCD, you need to look there. Are you using the 100 A c.t? (I see you didn't calibrate your emonTx). What values do you see for loads into the 3 - 5 kW region?

The easy way to check the GLCD is write a new sketch for your emonTx that completely ignores the inputs and simply writes a series of values to the output struct.

Comment out getting the currents and battery voltage, then add in loop( ) just above "if (settled)" something like:

emontx.power1 += 10;
emontx.power2 += 10;
emontx.battery += 10;
 

Then you should see the GLCD powers increase in steps of 10 W, and the battery voltage in steps of 10 mV, every 5 seconds. If they do that, the problem isn't with the nanode or the GLCD.

If that is OK, check the voltages at the c.t. burden resistors (18 Ohms). The voltage each end should be 1.65 V d.c. If not, check that you have pairs of 470 k resistors and the decoupling capacitors (10 uF) are the correct way round.

I have not looked at your code yet, but I doubt there is a non-linearity in the code.

I have now looked at your code, and I cannot see any a non-linearity in the code, it all looks absolutely standard. So I think it is a hardware / assembly problem in the emonTx.

thanks for your comment.....i will look at this.. and let you know.

many thanks

Check the current clamps - you need to make sure that there is no air gap between the surfaces of the jaws. That air gap can cause havoc.