Pressure sensor is a commonly used sensor, which can be applied to various industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent building, production automation, aerospace, military, petrochemical, oil well, electric power, ship, machine tool, pipeline and many other industries. .
Pressure sensor is a commonly used sensor, which can be applied to various industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent building, production automation, aerospace, military, petrochemical, oil well, electric power, ship, machine tool, pipeline and many other industries. . The following small series is simple for everyone to introduce the practical application and function of pressure sensors by taking cars, mobile phones and washing machines as examples.
Pressure sensor application example 1: car
The pressure sensor can be applied to the vehicle intake/exhaust management system, fuel vapor management system, brake boost system, and diesel particulate filtration system. Details are as follows:
1. Intake / exhaust gas management system
The automobile engine management system needs to inject a proper amount of fuel into the cylinder at an appropriate time, so that the fuel can be fully and effectively burned to achieve optimum combustion efficiency and reduce pollution. The engine manager's ECU decisions are based on a series of sensor signals such as crankshaft position, camshaft position, air flow, intake manifold temperature, intake manifold pressure, and the like. The intake manifold pressure sensor is a pressure sensor operating in an absolute pressure mode, and the ECU calculates the amount of fuel to be injected according to the pressure signal, so that the combustion process obtains an optimum air-fuel ratio. Vehicles equipped with an EGR system impose higher media compatibility requirements on the intake manifold pressure sensor.
2. Fuel steam management system
Since the volatilization of fuel is one of the main causes of hydrocarbon emissions, the fuel vapors of automobiles are mandated in the laws of some states in the United States. The fuel tank steam carrying the fuel steam management system enters the activated carbon tank through the separation valve through the pipeline. The activated carbon in the activated carbon tank is porous and has a large surface area, and can adsorb a large amount of fuel vapor molecules.
The activated carbon canister is connected to the intake manifold of the engine. When the engine is running on the intake stroke, the piston movement causes the intake manifold to generate a low pressure. Under the low pressure suction of the intake manifold, the air passes through the activated carbon canister, and the activated carbon canister The adsorbed fuel vapor molecules are sent to the engine for combustion to make full use, and the adsorption capacity of the activated carbon in the activated carbon tank is restored.
A micro pressure sensor (gauge mode) is required in the fuel vapor management system to detect fuel vapor leakage.
3. Brake assist system
The vacuum brake booster is the core component of the vacuum-assisted servo brake system, which utilizes the vacuum of the engine intake manifold and the differential pressure of the atmospheric pressure for brake assist. If there is air leakage in the brake boosting system, the pressure difference between the front and rear chambers of the air chamber during braking will be small or even disappear, and the brake boosting system will fail, resulting in increased braking distance and difficulty in braking. In addition, the direct injection system and the start-stop system enable the vacuum of the intake manifold of the vehicle to be reduced, and a vacuum pump is required to provide a vacuum source to meet the requirements of the brake boosting system.
In both cases, it is necessary to add a pressure sensor to monitor whether the pressure difference between the front and rear chambers of the air chamber is appropriate. If there is air leakage, the corresponding warning system should be activated. If the vacuum is not enough, the ECU should be notified to start the vacuum pump. Extra vacuum. The MLX90809 is a pressure sensor specially designed for this application. It can work in the differential pressure/gauge mode of 100KPa full scale and is suitable for brake booster applications.
4. Diesel exhaust gas filtration system
Due to the physical characteristics of the diesel engine, there are some tiny particles in the exhaust gas other than carbon monoxide, hydrocarbons and nitrogen oxides, which are the main causes of black smoke. In order to meet emission requirements and reduce environmental pollution, more and more diesel engines are equipped with Diesel Particulate Filter (DPF). When the exhaust gas generated by the combustion of the diesel engine passes through the diesel particulate filter, the porous system of the filter will capture the particles therein. When the diesel exhaust gas particles continuously accumulate in the filter, the filter will be saturated or even blocked, so it is necessary to The filter is regenerated.
The pressure difference between the filter inlet and the outlet is detected by a differential pressure sensor. When the pressure difference is higher than the set threshold, the filter is considered to be saturated, the ECU controls to increase the engine temperature, and the engine discharges the high temperature exhaust gas. The particles stored in the filter are burned to complete the regeneration of the filter. The MLX90807-1 can measure differential pressures from 40KPa to 200KPa for this application. Due to the high temperature of the exhaust gas and the presence of a variety of corrosive gases and particles, it is necessary to consider the problem of media compatibility.
5. Natural gas/liquefied petroleum gas fueled system
Due to the relatively low price of natural gas/liquefied petroleum gas, low exhaust pollution, safe and reliable, and simple vehicle modification, some countries and regions producing natural gas/liquefied petroleum gas are increasingly using natural gas/liquefied petroleum gas as fuel. In the case of retaining the original vehicle fuel supply system, a dedicated natural gas/liquefied petroleum gas unit is added to form a “dual fuel vehicle”.
The compressed natural gas/liquefied petroleum gas is stored in a cylinder, and the high pressure gas in the cylinder is sent to the combustion chamber through a pressure reducing valve and a pressure regulator to fully mix with the air and then burn to power the automobile. By separately monitoring the pressure of the air in the gas and intake manifold by two pressure sensors, the air-fuel ratio can be better controlled, the optimal combustion state is achieved, the fuel economy is improved, and pollution is reduced.
Pressure sensor application example 2: mobile phone
Due to technical and various reasons, the GPS calculation altitude is generally about ten meters in altitude, and sometimes it is not even receiving GPS satellite signals if it is in the woods or under the cliff. Fortunately, the range of options for measuring air pressure is greater. Moreover, the cost can be controlled to a relatively low range. In addition, some mobile phones not only have pressure sensors but also temperature sensors. In this way, more accurate judgments are made according to the temperature to improve the accuracy of the measurement results. Therefore, adding a pressure sensor based on the original GPS of the smartphone can make the positioning of the mobile phone more precise.
Pressure sensor practical application three: injection mold
Currently, there are two types of pressure sensors used in the cavity, namely, flat and indirect. The flat-mounted sensor is inserted into the cavity by drilling a mounting hole behind the cavity, the top of which is flush with the surface of the cavity, and the cable passes through the die to interface with the monitoring system interface on the outer surface of the die. . The advantage of this type of sensor is that it is not subject to pressure disturbances during demolding, but it is easily damaged under high temperature conditions, making installation difficult.
The above is the introduction of pressure sensor application examples. In addition to the above-mentioned automobile, mobile phone and injection molds, the pressure sensor can also be used in fully automatic washing machines. The application principle is to use the air chamber at different water levels. The change in pressure is detected as a change in air pressure, so that water injection into the washing machine can be automatically stopped at the set water level.