lZ series Variable-area Flow-meter with metallic measuring tube is the variable-area Flow-meter .As the fluid flow upwards in the metal tubethe floater moves upwards to a certain position where the force and the lift force and the gravitational force meets balanceat the orifice(or the cone tube) keeps fixed.The circulation area is in proportion to the height of the floaterit means the height of the floater represent the volume of the flow.When the floater moves up and down If transmit its position to the indicator moves following the movement of the floater and by using the carn board to show the value of flow linearly on the electricity remote transmit means so far as the needle of the indicator pointed out the value the flow-meter change the value into standard electric current signals of 4~20mA or 0~10mA accuracy using angle displacement sensor and electric circuit.