Water flow sensor works - Solutions - Huaqiang Electronic Network

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The water flow sensor is mainly composed of a copper valve body, a water flow rotor assembly, a steady flow component and a Hall element (see Fig. 1). It is installed at the inlet end of the water heater to measure the influent flow. As the water flows through the rotor assembly, the magnetic rotor rotates and the rotational speed changes linearly with the flow rate. The Hall element outputs the corresponding pulse signal to the controller, and the controller determines the magnitude of the water flow, adjusts the current of the proportional valve, and controls the gas volume through the proportional valve to avoid the phenomenon of summer warm and cool winter in the use of the gas water heater. . The water flow sensor fundamentally solves the shortcomings of the water pressure of the differential pressure type water-gas linkage valve and the dry burning of the flap type water valve. It has the advantages of sensitive, long life, quick action, safe and reliable, convenient connection and low flow rate (1.5L/min), which is well received by users.

The water flow rotor assembly is mainly composed of a turbine switch housing, a magnetic rotor and a brake ring. When using the water flow switch mode, its performance is better than that of the mechanical differential pressure disc structure, and the size is significantly reduced. When the water flows through the turbine switch housing, the magnetic rotor is pushed to rotate. When the different magnetic poles are close to the Hall element, the Hall element is turned on. The component is disconnected. Thereby, the rotor speed can be measured. According to the measured water flow rate, rotor speed and output signal (voltage) curve, the starting water pressure of the water heater and the starting water flow corresponding to the starting water pressure and the starting speed of the rotor can be determined. The control circuit can realize that the water heater starts to work when the rotor speed is greater than the starting speed; when the speed is lower than the starting speed, the water heater stops working. In this way, the water pressure of the water heater is generally set at 0.01 MPa, and the starting water flow rate is 3 to 5 L/min (the water temperature standard is required to meet the limit of the highest temperature rise). In addition, since the water becomes magnetized water under the magnetic field cutting of the permanent magnet material, the oxygen content in the water increases, which makes the person feel refreshed after bathing. The function of the brake ring is to stop the rotation of the magnetic rotor rotating at high speed and stop the pulse signal output when the water is stopped. The controller can not receive the pulse signal, immediately control the gas proportional valve to close the valve, cut off the air source, and prevent dry burning.

The water flow sensor measures the magnetic physical quantity using the Hall effect of the Hall element. A load resistor is connected to the positive pole of the Hall element while a DC voltage of 5 V is applied and the current direction is orthogonal to the direction of the magnetic field. When the water pushes the magnetic rotor through the turbine switch case, a rotating magnetic field of different magnetic poles is generated, and the magnetic induction line is cut to generate high and low pulse levels. Since the frequency of the output pulse signal of the Hall element is proportional to the rotational speed of the magnetic rotor, the rotational speed of the rotor is proportional to the water flow rate, and the gas water heater is started according to the magnitude of the water flow. The empirical formula for the pulse signal frequency is given by equation (1).

f=8.1q-3(1)

Where: f—pulse signal frequency, H2

Q—water flow, L/min

The value of the water flow is judged by the controller by the feedback signal of the water flow sensor. According to the different models of gas water heaters, the optimal starting flow rate can be selected to achieve ultra low pressure (below 0.02 MPa).