A wireless mouse for inputting commands to a host computer includes a casing, a control circuit, a wireless receiver, an electronic switch circuit and a resilient member. The apparatus for measuring particle distribution irradiates a laser beam to be measured, converts the resulting scattering light into an electrical detection signal, and performs inverse operation processes on the detection signal to calculate the particle size distribution of the sample. The first sampling circuit includes a first converter, a first phase interpolator, and a first sampler.