02 April 2022

Milliwatt meter with AD8318

Pushed by a friend who needed help with the firmware of a AD831x milliwatt meter, I (think I) decided to build a real circuit around the AD8318 module I have.

I used it for making differential power measurements of a 10 GHz generator to get the maximum juice out of it, so a voltmeter was enough to spot the lowest output voltage (the output is -25mV/dB, so the lower the better).

Nevermind. I have everything at home to build the whole power meter, so why not? I'm using PA0RWE Arduino firmware that is freely available and quite comprehensive. But his firmware was written for the AD8317, which has a different output slope (-22mV/dB) and different non-linearities.

I think that the slope value could be changed with a recalibration of the meter, but not the correction factors table. That's why I produced a different firmware with the right values for AD8318 (and I2C 16x2 display only) that will be up on my github repositories soon.