The vehicle sensor is an input device of the computer system of the car. It converts various operating condition information such as vehicle speed, temperature of various media, engine operating conditions, etc. into the electrical signal to the computer, so that the engine is at its best Working status. There are many automotive sensors. When judging a sensor’s failure, not only the sensor itself, but the entire circuit where the failure occurs should be considered. Therefore, when looking for faults, in addition to the sensors, check the wiring harnesses, connectors, and related circuits between the sensors and the electronic control unit.
There are three commonly used: 1. Classified according to the physical quantity of the sensor, it can be divided into sensors such as displacement, force, speed, temperature, flow rate, gas composition, etc.
2. According to the working principle of the sensor, it can be divided into sensors such as resistance, capacitance, inductance, voltage, Hall, photoelectric, grating, thermocouple and so on.
3. According to the nature of the sensor output signal classification, it can be divided into: switch type sensors with output values (“1” and “0” or “on” and “off”); Coded digital sensor.
A sensor is a device or device that can sense a specified physical quantity and convert it into a usable input signal according to a certain law. Simply put, a sensor is a device that converts non-electricity into electricity. The sensor usually consists of three parts: a sensing element, a conversion element and a measuring circuit.
1) Sensitive element refers to the part that can directly sense (or respond to) the measurement, that is, the sensitive element that is measured through the sensor is converted into a non-electricity or other quantity that has a certain relationship with the measurement.
2) The conversion element converts the above non-electric quantity into an electric parameter.
3) The function of the measurement circuit is to convert the electrical parameters input by the conversion element into measurable power such as voltage, current or frequency for processing, recording, control and processing.
Automotive sensors are widely used, such as: 1. The gasoline indicator is realized by a liquid level sensor. This liquid level sensor uses the level of the liquid level to convert it into a digital signal, which can be easily read from the meter.
2. Water temperature sensor. The water temperature sensor is a temperature measuring node installed in the water tank. When the water temperature is too high or too low, it can also alarm or read directly from the display instrument.
3, car air conditioner, the car air conditioner is controlled by the temperature sensor installed in the car, the temperature sensor has a temperature setting, when the temperature is too low, it will automatically start, when the temperature exceeds the temperature, it will automatically cool down
4, wiper sensor, the wiper is a sensor to sense the size of the rainwater, so as to control the frequency of the wiper, that is to say, the faster the rain is, the faster the rain is smaller.
5. The engine management system uses various sensors to convert the engine intake air volume, cooling water temperature, engine speed, acceleration and deceleration into electrical signals and send them to the controller. The controller compares this information with the stored information and outputs a control signal after accurate calculation. EMS not only can accurately control the fuel supply to replace the traditional carburetor, but also can control the ignition advance angle and idle air flow, which greatly improves the performance of the engine.
6. Principle of control system: The pedal information is transmitted to the throttle control module in the electronic controller through the pedal sensor installed on the accelerator pedal. The throttle control module calculates the throttle opening and drives the DC through a certain processing program. The motor completes the adjustment of the area of the throttle intake passage, thereby controlling the amount of intake air to meet the intake demand under different operating conditions of the engine.
7. Knock sensor function: Detects the vibration of the engine block, and uses the power supply controller to identify the engine knock conditions. Principle: The knock sensor is a vibration acceleration sensor. It is mounted on the engine cylinder block and can be mounted on one or more. The sensor’s sensitive element is a piezoelectric crystal. When the engine knocks, the engine vibration is transmitted to the crystal through the mass in the sensor. Due to the pressure generated by the mass vibration of the piezoelectric crystal, a voltage is generated on the two polar surfaces, and the vibration is converted into a voltage signal for output.
8. Idle speed regulator function: Provides an idle speed bypass air passage, and affects the bypass air volume by changing the cross-sectional area of the passage, so as to realize closed-loop speed control of the engine at idle speed.
9. Oxygen sensor function: Determine the oxygen content in the exhaust of the engine, and determine whether gasoline and air are completely burned. Based on this information, the electronic controller implements closed-loop control with the excess air coefficient λ = 1 as the target to ensure that the three-way catalytic converter has the maximum conversion efficiency of the three pollutants HC, CO and NOX in the exhaust.
10. Throttle position sensor Function: Provides engine load information and operating condition information.