Calibration

For the most accurate power measurements using the RF probe, it is essential to know the probe's Coupling Factor, that is, the conversion factor that accounts for the probe attenuation, in dB.

For a spectrum analyzer application, for example, set the analyzer's Reference Level Offset equal to the probe's coupling factor. After doing that, when you probe a point in the circuit, the analyzer will be calibrated to read power at that point in the circuit, as if you had opened the circuit and pigtailed in to make a power measurement.

A Note about Accuracy

The probe isn't as accurate as actually opening the circuit and pigtailing in, but it's a lot faster!

Because the probe is basically a voltage measuring device, not a power measuring device,  amplitude measurements will be affected by  SWR on the line being measured. Sometimes this will be an SWR measurement feature, and sometimes it will be a source of error. Accuracy is good, provided the VSWR at your measurement point is not excessive.

If VSWR is high along the line you are measuring, you can actually use the probe as a useful indicator of the VSWR on the line.

Precautions

Be careful not to let the ground pin touch a power trace while you are working!