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Types of Airbag Sensors

Types of Airbag Sensors

Modern automakers have equipped nearly all vehicles with advanced safety technology. With the increasing number of vehicles on our roads, airbag systems are the most common safety feature you’ll never lack.

For the airbags to operate, they require sensors. And today, you’ll learn about different types of airbag sensors.

Deaths and injuries have decreased with modern technology, unlike in the older days.

Airbag systems help the driver and passengers survive a crash that may cause injuries or death.

Although the airbags may not completely save the passengers from accidents, they reduce the impact. Thanks to the new technology.

Since the invention of airbags, reports indicate they have saved thousands of lives. However, the system is complex, and it needs a detailed explanation to understand how it works.

How an Airbag System Works

person holding black Volkswagen steering wheel in closed-up photo
Airbags

An airbag is made of stretchable material, mostly fabric, packed in various locations within the car interior.

Most airbags are located on the dashboard to protect the driver and passengers’ knees, heads, and chests.

Other airbags are located on the sides of the door and the roof. Airbag Control Unit controls the airbag system.

It’s a component that receives signals from the sensors and activates the airbag. Upon activation, the airbag fills within milliseconds to offer cushioning for the people.

Components of an Airbag Sensor

An airbag sensor is made of two different components;

  • Electrical Components

They contain an electrical circuit and a switch connecting the sensor to the airbag control unit. Once the switch is pressed to complete the circuit, the airbag control unit activates the inflator to fill the airbag.

  • Mechanical Components

Most mechanical components are made of a ball and a tube. A small magnet holds the ball on one side of the tube.

Once the collision happens, the ball is dislodged from the magnet and rolls forward. Upon reaching the end of the tube, it hits the electrical switch to complete the circuit.

In some sensors, you’ll find a roller spring-loaded with weight instead of a ball. It works the same as the ball by hitting the electrical switch to complete the circuit.

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black and gray car instrument panel cluster
Airbag location

Various Types of Airbag Sensors

1. Mass Type Sensors

The mass type sensors system contains two types of sensors. The airbag impact sensor is located at the vehicle’s front bumper. Positioning it at the front aims at the possible area a collision may occur.

Since most cars have engines at the front, it’s also set inside the engine. When the impact crosses the grill to the engine, the airbag control unit can accurately determine it’s a crash.

The second sensor is set on the dashboard. This safety airbag sensor on the dashboard monitors the seat belts and sends the data to the ACU.  These pairs are known as inertia sensors.

The mass crash sensor working principle is very simple. It has a sensing ball set inside a tube. As explained earlier, once the impact happens, the ball is pushed forward to activate a switch.

2. Roller Type Sensors

The roller-type sensors have weight connected to spring instead of a ball. When impact occurs, the metal weight is pushed forward.

This happens as a result of the coil spring tension alteration. The weight hits the switch and completes the circuit.

Roller-type sensors are just as common as the mass types. However, the type used in a car depends on the manufacturer.

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Airbag

The Airbag Control Unit

Without an airbag control unit, the system isn’t complete. It’s a complex component that you should first understand. All the sensors send the electrical impulses to the ACU once the circuit is complete.

The component uses these impulses to determine the impact level and activate the inflator. It has electrically transmitted metal pins that create an electrical arc. The arc activates a propellant of sodium azide (NaN3) that immediately burns.

When the sodium azide propellant decomposes, nitrogen gas fills the airbag. The bag inflates and protrudes to create cushioning.

How Many Airbag Sensors Are in a Car?

The number of airbag sensors varies depending on the vehicle manufacturer. In some cars, you’ll find two or more airbag sensors located right behind the front bumper. The other set is located inside the engine to monitor the deceleration rate. The third set is fixed around the dashboard and the passenger area, especially seat belts.

The seat belts sensor monitors the rate at which the passengers are thrown forward due to impact or emergency stop.

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What Are Different Types of Airbags?

There are four types of airbags found in most cars. Take a look;

  • Front Airbags

Front airbags are located on the steering or around the dashboard. They protect the driver and the front passenger in the event of a frontal crash. 

Further, they work in conjunction with the seat belts. For that reason, they may not offer protection if a side crash happens.

  • Knee Airbags

Knee airbags are installed on the lower part of the dashboard. When the collision occurs, they inflate to fill the gap between the dashboard and the driver’s or front passenger’s knees.

  • Side Airbags

There are two types of side airbags. The first is the torso airbag which protects the torso area. It’s usually located at the seat’s backrest. In an impact, it inflates between the door and the passenger.

The second type is the curtain airbag which deploys from the interior roof to protect the passenger’s head.

  • The Inflated Seat Belt

It protects the fragile bones of older people or children in the back seats. It inflates to offer cushioning on the shoulder, chest, and neck when a crash happens.

FAQs on Airbag Types

Can Airbag Sensors be Reused?

In most cases, the airbag sensors are reused unless they have been physically damaged. Especially if metallic objects crimp the signal wire connecting the sensor to the airbag control unit, you’ll have to replace the sensor.

What to Do After Replacing Airbags?

Once you remove the damaged airbags and replace them with new ones, you need to reset the sensors and the airbag control unit. Despite the types of airbag sensors you install, ensure they function to save you if there is another crash in the future. 

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