Which Sensor Used In Speedometer

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Which Sensor is Used in Speedometer?

A speedometer is an essential component in any vehicle as it displays the vehicle’s current speed. It allows the driver to maintain safe driving practices by constantly monitoring the speed of the vehicle. The accuracy of the speedometer is critical for advanced safety systems and regulatory compliance. To measure the speed accurately, a speedometer relies on the information provided by a specific type of sensor, known as a speed sensor.

What is a Speed Sensor?

A speed sensor is a device that measures and detects the motion of a vehicle. It records the rotational speed of the wheels or the transmission output shaft, converting it into an electrical signal that can be then interpreted by the speedometer. The speed sensor provides real-time information about the speed of the vehicle, allowing precise readings on the speedometer display.

Types of Speed Sensors Used in Speedometers

Several types of speed sensors are used in speedometers, depending on the vehicle’s design and technology. Let’s explore the different types of speed sensors commonly used:

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1. Hall Effect Sensor

The Hall effect sensor is one of the most commonly used speed sensors in modern speedometers. It operates based on the Hall effect, which involves the generation of a voltage when a conductor experiences a magnetic field. The Hall effect sensor measures the magnetic field created by a toothed wheel or a cogwheel as it rotates. As each tooth or cog passes the sensor, the magnetic field changes, causing a voltage output. By counting the number of voltage pulses per second, the speed sensor determines the rotation speed, which is then interpreted by the speedometer to display the speed.

2. Inductive Sensor

An inductive sensor is another type of speed sensor used in speedometers, particularly in older vehicles. This sensor relies on the principle of electromagnetic induction. It consists of a coil of wire that generates a magnetic field whenever an electric current flows through it. When a toothed wheel or a cogwheel approaches the inductive sensor, it disturbs the magnetic field, inducing an electric current in the coil. This change in current is measured by the speed sensor and converted into speed readings for the speedometer.

3. VSS Sensor

The VSS (Vehicle Speed Sensor) is a type of speed sensor commonly found in modern vehicles equipped with computer-controlled systems. It is typically located on the transmission output shaft or the differential. The VSS sensor utilizes either a magnet and a coil or a toothed wheel and a Hall effect sensor to measure the rotational speed. The sensor then sends an electrical signal to the vehicle’s onboard computer, which calculates the speed and sends the information to the speedometer.

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Importance of Speed Sensor Accuracy

The accuracy of the speed sensor is crucial for several reasons:

  1. The speedometer provides vital information for the driver to maintain safe driving practices and adhere to speed limits.
  2. Accurate speed readings are necessary for modern safety systems, such as anti-lock braking systems (ABS) and electronic stability control (ESC), to function correctly.
  3. A precise speed sensor ensures the accurate calculation of fuel consumption and mileage.
  4. Regulatory compliance requires speedometers to be within a specific tolerance range to avoid potential legal issues.

Factors Affecting Speed Sensor Performance

Several factors can affect the performance of a speed sensor. It is essential to consider these factors to ensure accurate speedometer readings:

1. Wheel Size

The size of the wheels can impact the speed sensor’s performance. If the vehicle’s wheels are replaced with larger or smaller ones, it can affect the speedometer’s accuracy. In such cases, the speedometer may need to be recalibrated to account for the changes in wheel diameter.

2. Gear Ratio

The gear ratio of the transmission can also influence the speed sensor’s performance. Different gear ratios can change the number of rotations required to cover a specific distance, affecting the accuracy of the speedometer readings.

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3. Sensor Calibration

Proper calibration of the speed sensor is crucial to ensure accurate readings. Over time, the sensor may require calibration or adjustment to maintain optimal performance. Regular maintenance and calibration checks can help prevent speedometer inaccuracies.

4. Sensor Positioning

The precise positioning of the speed sensor is essential for accurate speed readings. Any misalignment or improper installation of the sensor can result in inaccurate speedometer readings. It is crucial to follow the manufacturer’s guidelines and recommendations when installing or replacing a speed sensor.


Speed sensors are critical components of speedometers in vehicles. They provide real-time information about the speed of the vehicle, allowing drivers to maintain safe driving practices. The accuracy of the speedometer readings is essential for the proper functioning of safety systems and regulatory compliance. Hall effect sensors, inductive sensors, and VSS sensors are the most commonly used types of speed sensors in speedometers. Factors such as wheel size, gear ratio, sensor calibration, and positioning can affect the performance of the speed sensor and, consequently, the accuracy of the speedometer readings. Regular calibration, maintenance, and proper installation can help ensure optimal speed sensor performance and accurate speedometer readings.



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