Application of SM5420 pressure sensor in intake manifold

The intake manifold absolute pressure sensor (MAP), also known as the intake pressure sensor, is used in the D-type gasoline injection system. Its role in the gasoline injection system is to measure the intake volume and thus determine the injection volume. The intake manifold absolute pressure sensor measures the change in the absolute pressure (vacuum degree) in the intake manifold according to the load state of the engine , and converts it into a voltage signal, which is transmitted to the engine electronic control unit (ECU) together with the speed signal as the basis for determining the basic injection volume of the injector. In today's engine electronic control system, the most widely used is the semiconductor varistor intake manifold pressure sensor. The following introduces its structural principle and working principle. Structural principle The semiconductor varistor intake manifold absolute pressure sensor, whose pressure conversion element is a silicon diaphragm made by the piezoresistive effect of semiconductors. One side of the silicon diaphragm is a vacuum chamber, and the other side introduces the intake manifold pressure. The silicon diaphragm is about 3mm square, and the middle part is photoetched to form a thin film with a diameter of about 2mm and a thickness of about 50mm. There are 4 strain resistors around the film, which are connected in a single-arm bridge manner. Since one side of the film is a vacuum chamber, the higher the absolute pressure in the other side of the film, that is, the intake manifold, the greater the deformation of the silicon diaphragm, and its strain is proportional to the pressure. The resistance of the strain resistor attached to the film changes proportionally with the strain, so that the deformation of the silicon diaphragm can be converted into an electrical signal using a single-arm bridge. Because the output electrical signal is very weak, it needs to be amplified by a hybrid integrated circuit before output. The signal voltage output by this piezoresistive intake pressure sensor has the characteristic of increasing linearly with the increase of the absolute pressure of the intake manifold. Working principle of piezoresistive intake pressure sensor Strain resistors R1, R2, R3, and R4 form a Wheatstone bridge and are bonded to the silicon diaphragm. The silicon diaphragm can be deformed under the action of the absolute pressure in the manifold, thereby causing the change of the resistance value of the strain resistor R. The higher the absolute pressure in the manifold, the greater the deformation of the silicon diaphragm, and thus the greater the change of the resistance value of the resistor R. That is, the mechanical change of the silicon diaphragm is converted into an electrical signal, which is then amplified by the integrated circuit and output to the ECU. SM5420 Absolute Pressure SensorSM5420 is a small SO-8 packaged absolute pressure sensor. This product is a product of SMI in the United States. It is optimized based on the SM5108 sensor chip, with higher accuracy, and its packaging method is improved, using a single small package. This product adopts MEMS production technology and high-performance testing methods to maximize its working stability and ensure its superior performance. It has the characteristics of high sensitivity, good dynamic response, high accuracy, easy miniaturization and integration, so the sensor has been widely used in low-cost fields. Among them, the SM5420 chip has been widely used in the intake manifold absolute pressure sensor! SM5420 working characteristics and specifications.