Patent ID: 7219559

Claim:
A flow meter comprising: a taper-shaped tube which is made of an approximately transparent or semi-transparent material, is mounted approximately vertically, and circulates a fluid; a float which is arranged within said taper-shaped tube so as to be displaced in a vertical direction in correspondence to a flow rate of said fluid; a light emitting means which irradiates a light ray to said taper-shaped tube and said float, and transmits or reflects the light ray; a first mirror to which said transmitted or reflected light ray is input and reflected; a second mirror to which said transmitted or reflected light ray is input and reflected from said first mirror; an image sensor to which said transmitted or reflected light ray is input from said second mirror, and which outputs a digital image of said float within said taper-shaped tube; and a control portion which executes an input process of said digital signal, detects the position of said float within said taper-shaped tube, and outputs an electric signal showing said flow rate.