This is simple, cheap and quite robust device. It can be even calibrated if you have a reference: just insert it into reference source with the button pressed down, and it will show you which parameter can be adjusted and in what direction.
This is simple, cheap and quite robust device. It can be even calibrated if you have a reference: just insert it into reference source with the button pressed down, and it will show you which parameter can be adjusted and in what direction.