Making power measurements

One of the handy features of this detector is that it gives you an output voltage that is proportional to the RMS input power.

Tip

What is RMS?

Find out more about RMS at http://en.wikipedia.org/wiki/Root_mean_square#RMS_of_common_waveforms.

What this means to us is that we don't have to calculate the RMS power with our software; the chip does that for us. The schematic of the demo board is shown in the following diagram:

Demo board schematic (copyright Linear Technology Inc.)

The most important features of the schematic are the fact that the input is 50 ohms, single-ended (not double-ended, using a transformer), and the fact that the 3.3 V power is well filtered. This means that we do not have to worry about noise on the 3.3 V power coming from the BeagleBone.

In our case, the EN or Enable pin is simply connected to the 3.3 V rail, because I couldn't see any value in turning the detector on and off. If you want to do this, I suppose you could connect the...