Getting comfortable with your processes and instruments is important in any sort of investigation. There are so many ways to dowse and divine, just in the mechanical sense. You can simply use some body part; I use my right arm bent at the elbow and when I cross a "target" my right forearm swings about 4 inches inward toward my belly. When I pass over the spot my arm swings back to my side.
When I first began to dowse I used simple forked twigs, much to the chagrin of more experienced dowsers I met who were utilizing fancy L-rods, pendulums, and Y-rods made from exotic materials, with crystals on them, and others who used radionics devices with silver rubbing plates and calibration dials. We all got nearly the same results, but I got tired of mutilating a tree every time I wanted to dowse, so I stepped up to 12-gauge, solid copper electrical wire bent in half with a twist at the bend to keep it from breaking after repeated flexing. At first I had to be bare-handed and use stripped wire, but eventually I could work with thick mittens and plastic-coated wire. Since I first worked outdoors a lot, sometimes in severe cold with howling winds, these changes came in quite handy for obtaining speedy and reliable results.
The scales I use are arbitrary except when I'm trying to correlate the information I get with another means of measurement. Even MHz and GHz are arbitrary for my purposes, especially since many of the energies I find are not electromagnetic in nature, they may consist of multiple frequencies, and the frequencies may vary over time. For example, I find that ordinary underground water veins have a von Pohl intensity of -15 at night but -13 during daytime. They also change energy direction and their pattern shifts from 3 sets of 3 vertical planes at night to 23 equidistant vertical planes during daytime. I'm pretty sure that this much shifting in other aspects correlates with frequency shifts also.
Using dowsing and divination has become pretty habitual for me. I've used it in the past for water detection, location, depth soundings, flow rates, and potability studies (water is so easy to find here anyway). Back when I did soil consulting work for farmers I used it for a quick check of available nutrient levels, before I sent a soil sample off to a lab. I've checked eggs for fertility and sex. I've checked how long it takes for freshly-ground grains to become "dead". I've helped folks surreptitiously using a pendulum in our local natural food co-op to find the ideal food supplement. I've used it to find the current location (direction and distance; "divdar"?) of people I was waiting for. And, of course, I now look for energies of all sorts.
My point in all of this rambling is that it takes some time to figure out what works best for you. All I know is that I couldn't afford all of the fancy and expensive instrumentation it would take to achieve the above without dowsing. What I obtained more cheaply still required rigorous thought, some planning, loads of experimentation, cross-checking with other means of measurement, and patient practice. And the warranty hasn't expired on my equipment yet.
"Develop an infallible technique, then place yourself at the mercy of inspiration." (from a craftsman, but it applies widely)