A method includes obtaining a standard value for a characteristic of a power switch and obtaining a measured value of the characteristic, via a gate drive unit connected to a gate terminal of the power switch. The optical mouse also includes circuitry or a processor to detect bar codes and demodulate data encoded therein. Address data representing the position of the dust is stored in a memory that stores dust address data. The water filtration device is of unibody construction formed by ultrasonically welding certain parts thereof together.