Short Answer:

A Hall effect sensor works in speed measurement by detecting changes in magnetic fields caused by a rotating object. When a magnet or a toothed wheel with magnetic material passes near the sensor, it produces a voltage signal based on the Hall effect principle.

This signal is a series of electrical pulses, where each pulse corresponds to one movement or rotation. By counting the number of pulses in a given time, the system calculates the speed. Hall effect sensors are widely used because they are reliable, accurate, and function well even at low speeds.

Detailed Explanation:

Hall effect sensor in speed measurement

A Hall effect sensor is a type of active speed sensor that detects the presence and movement of a magnetic field. It uses the Hall effect principle, which states that when a current-carrying conductor is placed in a magnetic field, a voltage is generated perpendicular to both the current and magnetic field. This generated voltage is called Hall voltage and it is the key to detecting speed in rotating systems.

Hall effect sensors are commonly used in automotive speedometers, anti-lock braking systems (ABS), motor control systems, and various industrial applications due to their accuracy and ability to operate in different conditions.

Working Principle:

1. Sensor Placement:
   The Hall sensor is positioned near a rotating part such as a gear wheel, shaft, or magnet disc. This rotating part has magnetic elements or passes by a magnet attached to the sensor.
2. Magnetic Field Change:
   As the object rotates, the magnetic field near the sensor changes — either by passing a magnet near the sensor or by changing the magnetic pattern of a gear tooth or notch.
3. Hall Voltage Generation:
   When the magnetic field changes, it affects the Hall element inside the sensor, causing a small voltage to be generated. This Hall voltage is proportional to the magnetic field strength.
4. Signal Processing:
   The Hall voltage is very small, so it is amplified and converted into a digital pulse or analog signal. Every time the rotating magnetic field passes by, a pulse is generated.
5. Speed Calculation:
   The number of pulses per second is counted by a microcontroller or speed monitoring circuit. The speed is calculated using the formula:

Speed (RPM)=Number of Pulses per Second×60Number of Poles or Teeth\text{Speed (RPM)} = \frac{\text{Number of Pulses per Second} \times 60}{\text{Number of Poles or Teeth}}Speed (RPM)=Number of Poles or TeethNumber of Pulses per Second×60​

This provides a real-time measurement of the rotational speed.

Advantages of Hall Effect Sensor:

• Works at low and high speeds
• Non-contact sensing – no physical wear
• Durable and long-lasting
• Accurate and reliable output
• Immune to dust, oil, and vibrations

Limitations:

• Requires power supply to operate
• Only works with magnetic materials or magnets
• May be affected by strong external magnetic interference

Applications:

• Automobiles: Engine and wheel speed sensing
• Motors: Rotor position and speed detection
• Robotics: Wheel and joint movement monitoring
• Conveyor belts and industrial machines
• Tachometers and electronic speedometers

Conclusion:

A Hall effect sensor measures speed by detecting changes in a magnetic field caused by a moving object. It generates electrical pulses every time a magnetic field passes near it, and by counting these pulses over time, the system calculates the speed. This method is accurate, fast, and suitable for various conditions, making Hall effect sensors highly valuable in electrical and mechanical speed measurement applications.