I will make this short and sweet: nobody has any business using a moisture meter on concrete unless it's a concrete moisture meter. A concrete moisture meter is an expensive one-trick pony I've never owned. They're useful if you're going to install a floor covering over concrete, and that's about all. For this reason, I've never owned a concrete moisture meter, and I surely never will. As a home inspector, I have no use for this tool.

If I try using my wood moisture meter on concrete, it'll peg my meter. This doesn't mean the concrete is wet; it just means I'm using the wrong tool for the job.