I have gone through about three different radiation detectors from Amazon and they all ended up in the trash. They were either impossible to calibrate or just gave random numbers that didn't make sense. I finally decided to invest in a Milerd HiRange after seeing a review on a tech blog. The difference is night and day. The interface is actually understandable for a normal person—it shows you the current levels and accumulates data so you can see spikes over time. I really like that it separates electric and magnetic fields because they need to be treated differently. It's also super small, like a highlighter pen, so I take it with me when I travel for work to check hotel rooms. If you are serious about monitoring your exposure, don't waste money on the cheap yellow plastic ones. This one is accurate, holds a charge for a week, and actually detects the modern frequencies we worry about.