【 Weak current College 】 water flow sensor principles and applications-Power By 【 China power house network 】

A basic principle

Water flow sensor is the use of the Hall element of Hall effect to measure the magnetic physical quantity. In the Hall elements of cathode conspiracy into load resistance, at the same time pass on 5V DC voltage and current direction and magnetic field direction orthogonal. When the water through the turbo switch magnetic rotor spinning shell advance, produce different poles of the rotating magnetic field, the magnetic wire cutting, high and low pulse level. Because of the Hall element of the output pulse signal frequency and magnetic rotor speed proportional to the rotor speed and flow proportional to the size of the under water heater starts. The pulse signal frequency experience formula see-(1).
f=8．1q-3(1)
Type: f-pulse signal frequency, H2
Q-flow, L/min
The water flow sensor feedback signal through the controller to determine the value of the water flow. According to the different gas heater model, choose the best boot volume, you can achieve ultra low voltage (0.02MPa) started.

The second principle of work

Water flow sensor is mainly composed of copper valve, flow rotor components, steady flow component and Hall components (see Figure 1). It is mounted on the inlet side of the water heater is used to measure water flow. When water flows over the rotor component, magnetic rotor rotation and speed change linearly with the flow. Hall element output the appropriate pulse signal back to the controller, the controller determines the size of the water, adjust control proportional valve's current to adopt proportional valve control gas volume, avoid the use of gas water heaters in summer and warm winter during cool phenomenon. Water flow sensor fundamentally solves pressure differential pressure of the water-oil valve starts and tipping water valve is easy to miss the action appears dry heating and shortcomings. It has a reflecting sensitive, long life, fast action, safety and reliability, connect the flow to facilitate launch ultra low (1.5L/min), etc., by the majority of users.


Figure 1 the structure of the water flow sensor

-Flow rotor components mainly by turbine switch shell, magnetic rotor, brake ring. Use the current switch modes, its performance advantages over mechanical pressure differential disk structure and size significantly narrowed. When the water flow through the turbine driven magnetic switch shell, rotor rotation, different pole near the Hall element, a Hall element on-time departure hall element is disconnected. From here, you can measure out the rotor speed. According to the measurement of water flow and rotor speed and output signals (voltage) of the curve, you can determine the start of the water heater, water pressure and start pressure corresponds to the start of the water and the rotor speed start. The control circuit, we can achieve when the rotor speed is greater than the start when you start the work speed; the water heater at speed is less than start speed, water heaters and stop working. This water heater starts in hydraulic General settings, start the water flow to 0.01MPa 3 ~ 5L/min (required to meet the water heater standard on maximum temperature rise limitation). In addition, because the water in the magnet magnetic cutting, become magnetized water, the oxygen content in the water increases, so people feel refreshed after bathing. Brake ring is shut off, the Suppression of high-speed rotating magnetic rotor rotation, termination of pulse signal output. Controller not receive pulse signal, immediately control combustion proportional valve closing valve, cut off the gas to prevent ganshao.

Three water flow sensor and comparison of air-oil valve

Pressure-water and oil valve disadvantage is the high water pressure startup, and to reduce water pressure need to sacrifice some steady flow characteristics (flow-pressure fluctuations of stable capacity). In order to be able to make both, only intensify the water valvediaphragm, such as the body increases costs will rise, and the flow starting pressure indicators cannot go too low. On the water flow sensors, in the water-side to increase stability, steady flow components. Ring of geometry and physical performance, through the test successfully developed apply to different capacity water heaters of steady flow components, has good stability characteristics (inlet pressure variation in 0.1 ~ 0.5MPa, yield change in 3L/min), ensure that the water pressure variation, maintain flow in a certain range, reached the thermostatic effect.
Compare pressure-water and oil valve and flow sensors, can be seen, the former is a more complicated mechanical, structural, small and great, but the control circuit is simple; the latter is electrical, relatively simple structure, small size, but the control circuit of the complex. More important is the former high water pressure startup, waterway system resistance, it is not advisable to use larger in 10L/min or more bulk water heater AZ; while the latter started water down the waterway system resistance is small, in more than 10L/min bulk water heater has been widely used.

IV conclusion

In recent years, the use of water flow sensor measuring flow in strong type Digital thermostat heater in a large number of applications as it turns out, uses water flow sensor has a simple structure, high reliability, a wide range of measurement, etc. If you can match the combustion proportional valve for gas ratio adjustment, can achieve gas water heater in the combustion process of automatic control.