The metal float flowmeter is an area flowmeter, which means that in the vertical measuring tube of the flowmeter, when the fluid flows upward through the tube, the float moves upward, and at a certain position, the lift and gravity of the float reach equilibrium. At this time, the flow clearance area between the float and the orifice plate (or cone tube) remains constant. The annular gap area is proportional to the rising height of the float, that is, a certain height of the float represents the size of the flow rate. When the float moves up and down, the position is transmitted to the external indicator in the form of magnetic coupling, so that the pointer of the indicator follows the movement of the float, and with the help of the cam plate, the pointer linearly indicates the size of the flow value. The electric remote transmission type is to accurately convert the flow value into a standard signal of 0-10mA or 4-20mA through the angle sensor and electric transmission circuit while indicating on site.