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Home > MEMS / sensing technology > How many sensors in car

How many sensors in car

Published time: 2020-08-24 16:02:40

Nowadays, cars are becoming more and more intelligent, and many functions on cars are controlled by computers, such as engine system, gearbox system, suspension system, braking system, air conditioning system, body control system and so on. To control these systems, the computer must get the correct information to confirm the state of the system, and then issue the correct instructions to control the actions of the system, so as to execute the driver's intention and control the car correctly. The information that reflects the state of the system is completed by a component called a sensor, which can convert the light, electricity, temperature, pressure, time, speed and other information of the car in operation into electrical signals, and then input them into the on-board computer system, and then The calculation and analysis are carried out by the pre-stored program in the computer to judge the running state of the car.

There are a lot of sensors on cars nowadays, even for a very ordinary car, there are as many as dozens of sensors, and even more advanced cars have as many as hundreds. It is like our eyes, ears, nose, and skin. It converts all the information we see, hear, smell, and feel into electrical signals, which are transmitted to the car’s computer system so that the car can make correct Judging, assist the driver to better control the vehicle. With the advancement and development of technology, cars are becoming more intelligent, and there will be more and more sensors in cars. Below we respectively talk about the names and functions of the main sensors in each system of the car.

1. Air flow sensor (MAF)

The function of the air flow sensor (MAF) is to convert the amount of air drawn into the engine cylinder per unit time into an electrical signal and send it to the engine control module (ECU). It is one of the basic signals that determine the fuel injection volume and ignition timing.

According to its structure type and the detection principle of intake air volume, it can be divided into wing plate air flow sensor (MAF), Karman vortex air flow sensor (MAF), hot wire air flow sensor (MAF), hot film air flow sensor (MAF) ) Four types, the hot wire type and the hot film type are the most used now.

If the air flow sensor fails, the engine will be difficult to start, abnormal performance, unstable idling, tempering, firing during acceleration, high fuel consumption, and deflagration.

Air flow sensor.png

2. Intake manifold pressure sensor (MAP)

The function of the intake manifold pressure sensor (MAP) is to detect the vacuum degree of the intake manifold and convert the pressure signal into an electronic signal to be sent to the engine control computer. It is the main reference signal for controlling the fuel injection pulse width and ignition timing

Divided into two kinds of semiconductor varistor type and capacitive intake manifold pressure sensor.

If the intake manifold pressure sensor fails, the engine will have difficulty starting, abnormal performance, poor acceleration, unstable idling, high fuel consumption, unstable acceleration, tempering, firing during acceleration, high fuel consumption, deflagration and other malfunctions.

3. Crankshaft position sensor (CKP)

The crankshaft position sensor (CKP) is one of the most important sensors in the centralized engine control system. It is an indispensable signal source for confirming the position of the crankshaft angle and the engine speed. The engine control module (ECU) uses this signal to control the amount of fuel injection and fuel injection. Timing, ignition timing (ignition advance angle), ignition coil charging closing angle, idling speed and operation of electric gasoline pump.

According to the principle of signal formation, the crankshaft position sensor (CKP) can be divided into three categories: electromagnetic type, photoelectric type and Hall effect type.

When the crankshaft position sensor fails, the engine cannot start, poor acceleration, unstable idle speed, intermittent flameout and other malfunctions.

4. Camshaft position sensor (CMP)

The camshaft position sensor is used to detect the angular position of the camshaft. The engine control module (ECU) uses this signal to determine the cylinder sequence of the engine to control the injection sequence and ignition sequence

When the camshaft position sensor fails, the output power of the engine will decrease.

5. Engine coolant temperature sensor (ECT)

The engine coolant temperature sensor is used to detect the temperature of the engine coolant, and convert the temperature signal into an electrical signal and send it to the engine control module (ECU) as the main correction signal for gasoline injection, ignition timing, idle speed and exhaust emission control.

6. Intake air temperature sensor (IAT)

The intake air temperature sensor is used to detect the intake air temperature, and convert the intake air temperature signal into an electrical signal and send it to the engine control module (ECU) as a correction signal for gasoline injection and ignition timing.

7. Exhaust temperature sensor

The exhaust gas temperature sensor is used to detect the temperature of the recirculated exhaust gas to reflect the flow rate of the exhaust gas recirculation.

Exhaust temperature sensor.png

If the engine temperature sensor fails, it will be difficult to cold start the car at very low temperatures, poor driving characteristics during the warm-up phase, increased fuel consumption, and increased exhaust emissions.

8. Throttle opening sensor

Throttle opening sensor is used to detect the opening of the throttle valve and the speed of opening and closing, and convert the signal into a voltage signal and send it to the control computer of the engine, which is used to control the injection pulse width, ignition timing, idling speed, exhaust emission The main correction signal is also an auxiliary signal for the air flow sensor or intake manifold pressure sensor.

If the throttle opening sensor fails; the engine is difficult to start, the idle speed is unstable, the engine performance is poor, and the engine is easy to stall, and there will be bumps when the load changes during deceleration.

Throttle opening sensor.png

9. Oxygen sensor

The fundamental function of the oxygen sensor is to detect the oxygen concentration in the exhaust gas, and then the ECU (engine system control computer) will use the oxygen concentration signal provided by the oxygen sensor to determine the combustion status of the engine (front oxygen) or the working efficiency of the catalytic converter (rear oxygen). There are zirconia type and titanium oxide type.

If the oxygen sensor fails, the engine performance is poor, the lambda adjustment is fixed, the idle speed is unstable, the emission value is abnormal, the fuel consumption increases, and the spark plug deposits carbon

Oxygen sensor.png

10. Knock sensor

The knock sensor is used to detect whether knock occurs during the combustion process of the engine, and send the knock signal to the engine control computer as an important reference signal for correcting the ignition advance angle

There are two types of knock sensors: non-resonant type and resonant type. They are generally installed between cylinders 2 and 3, or one between cylinders 1, 2 and one between cylinders 3 and 4. The connecting wires of general knock sensors are wrapped with shielded wires.

When the knock sensor fails, the engine will deflagrate, the ignition timing will be inaccurate, the fuel consumption will be high, the power will be reduced, and the engine will work rough

11. Oil pressure sensor

The oil pressure sensor is used to detect the engine oil pressure and send out an alarm signal when the pressure is insufficient. When the oil pressure is insufficient, the oil lamp on the dashboard will light up. There are generally two, one on the main oil passage and one on the cylinder head.

12. Vehicle speed sensor

The vehicle speed sensor is generally installed near the output shaft of the transmission. It is an electromagnetic induction speed sensor used to detect the speed of the output shaft of the transmission. The computer calculates the vehicle speed based on the signal from the vehicle speed sensor as the basis for its shift control.

13. Hydraulic oil temperature sensor

Installed on the valve plate in the oil pan of the automatic transmission, it is used to detect the temperature of the hydraulic oil of the automatic transmission, which is used as the basis for the computer to control the gear shift, oil pressure and lock-up clutch. Inside the hydraulic oil temperature sensor is a semiconductor thermistor, which has a negative temperature resistivity. The higher the temperature, the lower the resistance, and the computer measures the temperature of the hydraulic oil in the automatic transmission based on the change in resistance.

14. Automatic gearbox multi-function switch

The multi-function switch is also called the gear switch. Its function is to convert the mechanical movement of the shift lever into an electrical signal, which is transmitted to the automatic transmission electronic control unit to control the gear position of the transmission.

15. Wheel speed sensor

The wheel speed sensor is a sensor used to measure the speed of a car wheel. For modern cars, wheel speed information is indispensable. Vehicle dynamic control system (VDC), automotive electronic stability program (ESP), anti-lock braking system (ABS), automatic transmission control system, etc.速信息。 Speed information. Therefore, the wheel speed sensor is one of the most critical sensors in modern cars. The commonly used wheel speed sensors mainly include: magnetoelectric wheel speed sensors and Hall wheel speed sensors.

16. Brake light switch

The brake light switch is also called the brake light switch. Its function is to control the turning on and off of the brake light, and to coordinate the coordinated operation of the vehicle with ABS/EBD or related braking and body stabilization systems, and the automatic transmission P gear unlocking, etc. . Nowadays, the brake light switch is a very important sensor in the car. If it fails, many functions of the car will not be able to perform or even exercise.

17. Steering wheel angle sensor

It is a device used to detect the rotation angle and direction of the steering wheel. The steering wheel turning left or right will be detected by the steering angle sensor, so that the car's electronic control unit will issue the correct steering command. The turning angle of the steering wheel is to provide the basis for the car to realize the steering range, so that the car can drive according to the driver's steering intention. In the automobile body stability control system and the electric power steering system, the steering wheel angle sensor is a very important signal.

18. Air conditioning system sensor

(1) Temperature sensor The temperature sensors inside and outside the car are all negative temperature coefficient thermistor sensors, which are used to sense the temperature inside and outside the car. When the temperature changes, the resistance of the thermistor changes, thereby sending a temperature signal to the air conditioning electronic control unit (ECU).

(2) Evaporator temperature sensor This sensor is used to detect the temperature of the air passing through the evaporator or the temperature change on the surface of the evaporator, and to control the engagement or disconnection of the electromagnetic clutch of the compressor.

(3) Coolant temperature sensor The coolant temperature sensor is directly installed on the water channel at the bottom of the heat exchanger to detect the temperature of the coolant. The generated coolant temperature signal is sent to the electronic control unit (ECU) to control the speed of the blower at low temperatures. 

(4) Sunshine sensor Sunshine sensor is a photodiode that uses the photoelectric effect to convert the change in the amount of sunlight into a change in current value and send it to the air conditioner electronic control unit to adjust the air volume and temperature blown by the air conditioner.

19. Security system sensors

There are mainly collision sensors, safety sensors, central airbag sensors, seat belt sensors, occupant difference sensors, etc. The collision sensors are divided into front collision sensors and side collision sensors. The main function is to determine the intensity and orientation of the collision when the car collides, and then determine whether the airbag is detonated.

20. Fuel tank level sensor

The fuel level sensor of the gasoline tank uses a float to float up and down in gasoline. The fuel level sensor is actually a variable resistor. If there is more gasoline, the float will float to a high position. If the gasoline is low, the float will be in a low position. The resistance of the float is different at different positions, and the computer converts the resistance to the voltage to detect the amount of gasoline.

There are many sensors on the car, such as door switch sensors, longitudinal and lateral acceleration sensors of the body, light system sensors, etc. In short, the sensors on the car are very important. Without them, the electronic control unit cannot know the running status of the car.  Of course, it cannot effectively control the vehicle. So if the car has some control failure, we must first check the working status of these sensors.


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