Amazing meter for price - all the name brand ones are 10-20x the price, and this meter provides a numerical read-out that seems to increment in small steps (100Mohm, 110Mohm, etc). You can buy large value (1G/10GOhm) resistors to check calibration too (they are SMD resistor so need some wire bodges). But mostly you only need a very rough estimate to check ESD ratings, and it seems at least accurate enough to serve that purpose. Test voltage seems to always be 10V, but may be it's switching at another voltage than standard suggests. Doesn't seem to affect actual read-out however, so I think they are just designing it based on what is needed and not the standard.