I use one, both in the studio and outside.

Never had any problems.

Remember that what your camera meters and what your meter is reading, can differ greatly, depending on what metering mode you have set your camera to, the meter doesn't have spot readings either, not matrix, not center weighted etc.

I don't know....I just trust it, but I make sure to meter correctly and several times to avoid any misreadings/errors on my part when I am outside.