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What is a Hall Effect Sensor and How Does It Work?

Author: Apogeeweb
Date: 13 May 2021
 2393
How Does a Hall Effect Sensor Work

Ⅰ Introduction

The Hall Effect is the most common method of measuring magnetic fields, and Hall Effect Sensors are widely used and have a wide range of applications in modern times. For example, they're used in cars as wheel speed sensors and crankshaft or camshaft position sensors. They're often used as switches, MEMS compasses, proximity sensors, and other applications. Now we'll take a look at a few of these sensors to see how they function, but first, let's define the Hall Effect.

 


Catalog

Ⅰ Introduction

Ⅱ What is Hall Effect

Ⅲ What is a Hall Effect Sensor

Ⅳ How Does a Hall Effect Sensor Work

Ⅴ Hall Effect Sensor Types

  5.1 Threshold

  5.2 Linear

Ⅵ Hall Effect Sensor Uses

  6.1 Head-on Detection

  6.2 Sideways Detection

Ⅶ Hall Effect Sensor Applications

  7.1 Hall Effect Sensor in Rotary Applications

  7.2 Hall Effect Sensor in Proximity Applications

  7.3 Proximity Hall Effect Sensor Uses in Robotics

Ⅷ How to Test Hall Effect Sensors

Ⅸ FAQ

 


Ⅱ What is Hall Effect

The experiment that describes the Hall Effect is as follows: If we have a thin conductive plate like the one shown and apply current to it, the charge carriers will flow in a straight line from one side to the other.

what is hall effect-explain

Now, if we apply a magnetic field near the plate, we can disrupt the charge carriers' straight flow due to a force known as the Lorentz Force. The electrons would deflect to one side of the plate, while the positive holes would deflect to the other. This means that if we now connect the other two sides with a meter, we can get a voltage that can be measured.

what is hall effect-electrons

As previously mentioned, the effect of obtaining a measurable voltage is known as the Hall Effect, after Edwin Hall, who discovered it in 1879.

 

 


Ⅲ What is a Hall Effect Sensor

A Hall Effect sensor detects changes in magnetic field power. This sensor opens up a wide range of possibilities for robotic sensor applications.

They can be used in applications such as proximity, positioning, speed, and current sensing. They're usually used on pneumatic cylinders, where they're used to communicate the cylinder's position to a PLC or robotic controller.

what is hall effect sensor

Automotive, personal electronics, and robotics are only a few of the industries that use Hall Effect sensors. Depending on the application, they have some advantages over other sensors.

 

They are fully encased because they operate with a magnetic field, making them less vulnerable to damage from dirty or wet conditions. They are less likely than mechanical systems to wear out or skew readings after a large number of cycles.

 

Hall Effect sensors are useful for a wide range of applications due to their reliability and longevity since they do not need physical contact to operate properly. They can provide more repeatability and accuracy than mechanical units because they do not physically interfere with the machinery or tooling.

 

 


Ⅳ How Does a Hall Effect Sensor Work

It's best to start with the basics of the Hall Effect to comprehend a Hall Effect sensor. As current flows through a conductor in the presence of a magnetic field, the electrons are pushed to one side of the conductor by the magnetic field.

 

The Hall Effect can be used to measure electric current in conductors that are built with certain parameters in view. The voltage across a flat metallic conductor, for example, reveals the Hall Effect much better than the voltage across around one.

how does a hall effect sensor work

The electrons moving over the conductor are forced to one side when a magnetic field is applied to the flat plate. Since the sum of deflection can be calculated, the apparatus has a wide range of applications.

 

A flat plate conductor is used to calculate magnetic strength in a Hall Effect sensor. When a magnet gets close to the sensor, the sensor detects it and sends the information to a controller.

 

The charge across the plate is shifted to one side while the magnet is near the sensor, producing a positive charge on one side and a negative charge on the other. The voltage difference between the two sides of the plate is determined, and it can be used to calculate magnetic strength or sensor proximity.

 

 


Ⅴ Hall Effect Sensor Types

Hall Effect Sensors come in two basic types:

5.1 Threshold

When the field strength reaches a certain amplitude and/or polarity, the threshold (also known as digital or on-off) produces a constant hall voltage. There are several different threshold device configurations, such as latching devices that turn on when a positive field strength reaches the threshold but only turn off when a negative field of the same strength reaches the threshold, devices that turn on when only a positive field reaches the threshold but are off otherwise, and devices that turn on when either a positive or negative field reaches the threshold. Thresholds can also be programmed in some computers.

Types of hall effect sensors-threshold

 

5.2 Linear

Linear (analog output sensor) generated a hall voltage proportional to the magnetic field strength around it. The polarity of the voltage swing is determined by the direction of the surrounding magnetic field. When expressive movements must be sensed as small changes in position, linear devices are more commonly used in musical applications.

Types of hall effect sensors-linear

 


Ⅵ Hall Effect Sensor Uses

Hall effect sensors are powered by a magnetic field, and in many applications, a single permanent magnet connected to a moving shaft or device may control the device. There are many different forms of magnet sensing motions, including "Head-on", "Sideways", "Push-pull", and "Push-push" among others. To ensure optimum sensitivity, magnetic lines of flux must always be perpendicular to the sensing region of the system and of the right polarity, regardless of the configuration.

 

High field strength magnets with a significant change in field strength for the necessary movement are also required to ensure linearity. There are several ways to detect a magnetic field, and two of the most common sensing configurations using a single magnet are shown below: Head-on detection and sideways detection are two types of detection.

 

6.1 Head-on Detection

Head on detection

The magnetic field must be perpendicular to the hall effect sensing system and approach the sensor straight on towards the active face for "head-on detection" as the name suggests. In a way, it's a "front-on" approach.

 

This direct approach produces an output signal, VH, which in linear devices reflects the magnetic field power, or magnetic flux density, as a function of distance from the hall effect sensor. The output voltage increases as the magnetic field gets closer and hence stronger, and vice versa.

 

Positive and negative magnetic fields can also be differentiated by linear instruments. For indicating positional detection, non-linear devices can be made to trigger the output "ON" at a pre-set air gap distance away from the magnet.

 

6.2 Sideways Detection

Sideways detection

"Sideways detection" is the second sensing configuration. This necessitates moving the magnet sideways across the face of the Hall effect element. For example, counting rotational magnets or measuring the speed of rotation of motors, sideways or slide-by detection is useful for detecting the presence of a magnetic field as it travels across the face of the Hall element within a fixed air gap distance.

 

A linear output voltage representing both a positive and negative output can be generated depending on the direction of the magnetic field as it passes by the sensor's zero-field centerline. This enables the identification of directional movement in both vertical and horizontal directions.

 

Hall Effect Sensors have a wide range of applications, especially as proximity sensors. Where the environmental factors include water, vibration, dirt, or oil, such as in automotive applications, they can be used instead of optical and light sensors. Present sensing can also be done with Hall effect instruments.

Sideways detection-electromagnetic field

A circular electromagnetic field is formed around a conductor when a current passes through it, as we learned in previous tutorials. Electrical currents ranging from a few milliamps to thousands of amperes can be calculated from the induced magnetic field by placing the Hall sensor next to the conductor without the use of large or expensive transformers and coils.

 

Hall effect sensors can be used to detect ferromagnetic materials such as iron and steel, in addition to detecting the presence or absence of magnets and magnetic fields, by putting a small permanent "biasing" magnet behind the active region of the device. Any shift or disruption to this magnetic field caused by the introduction of a ferrous material can be detected with sensitivities as low as mV/G.

 

Depending on the type of device, whether digital or linear, there are a variety of ways to connect Hall effect sensors to electrical and electronic circuits. The use of a Light Emitting Diode, as shown below, is a very simple and easy-to-build example.

 

Hall effect sensors can be used in a variety of ways due to the different magnetic movements. In both industrial and domestic environments, the most common application for these instruments is to measure objects' presence, position, and proximity.

 

Current sensors, pressure sensors, and fluid flow sensors are all popular applications for Hall effect sensors in industrial and manufacturing processes. In current transformers, Hall effect sensors are an inexpensive, contactless way to measure DC magnetic flux.

 

 


Ⅶ Hall Effect Sensor Applications

7.1 Hall Effect Sensor in Rotary Applications

Speed sensors operate by counting the number of times a shaft or disk rotates in a given amount of time. A disk attached to the motor shaft rotates next to the Hall Effect sensor and has magnets on its perimeter.

 

The state of the sensor is shifted as the magnets move through it. Based on this data, the sensor calculates the revolutions. For example, if the disk or shaft has four magnets, the sensor can switch states four times per revolution.

Hall Effect Sensor in Rotary Applications

This enables the sensor to measure the RPM based on the known parameter that four pulses per revolution will occur.

 

This technology is used in brushless DC motors to track speed and detect shaft position. This enables them to run at specific RPM ranges while still allowing them to change the motor speed at any time.

 

This makes controlling the motors a lot easier. It also allows them to monitor the location of the shaft on the motor, making them much more flexible in the robotics industry than motors without Hall Effect sensors.

 

7.2 Hall Effect Sensor in Proximity Applications

Based on a magnetic field, Hall Effect sensors can detect proximity. If the magnetic field strength is constant and defined, the position of the sensor in relation to the magnet can be determined.

 

When a magnet moves into its range, the sensor changes states and alerts the controller. Proximity Hall Effect sensors can be used in a variety of ways. Robotic tooling, robotic grippers, pneumatics, and a variety of other non-robotic applications use them.

Hall effect proximity sensor

7.3 Proximity Hall Effect Sensor Uses in Robotics

Proximity Hall effect sensors can also be used in robotics. They're good for detecting magnetic strength and magnet proximity. Hall Effect sensors may be used to meet a variety of safety requirements. They are often used in tooling to provide clamp confirmation to the controlling device.

 

Clamp confirmation locks the cell's operation until all sections are fully clamped, allowing it to function safely. Magnets embedded in the tooling that fall within the sensing range of the Hall Effect sensor when properly clamped normally dictate part confirmation. The robotic controller or PLC knows the cell is safe to operate when all sensors display a signal.

 

In the robotics industry, Hall Effect sensors are extremely useful. For sensing changes in the cell, most robotic cells use a Hall Effect sensor. They are used to read the speed and position of DC brushless motors. They are used in pneumatic cylinders to determine if the cylinder is extended or retracted.

 

They can also be used to keep staff healthy by notifying the controlling body of tooling clamp confirmation. Without Hall Effect sensors, the robotics industry will be very different.

 

 


Ⅷ How to Test Hall Effect Sensors

The camshaft and crankshaft position sensors are Hall effect sensors that control the camshaft and crankshaft position, respectively. In front of the sensor, a small magnet passes. The output voltage increases as the magnet get closer to the sensor. The voltage drops as the magnet moves away from the sensor. To assess shaft position, the electronic control module tracks these sensor outputs. The ECM can maintain precise engine control thanks to the camshaft and crankshaft position sensors, as well as other electrical sensors, solenoids, and injectors. Understand the basics of Hall effect sensors will aid you in properly testing a questionable sensor.

 

• Step 1

Remove the sensor from the engine block. Remove any oil, dirt, or metal shavings from the sensor tip.

 

• Step 2

Examine the engine's schematic for the camshaft sensor or crankshaft signal to the ECM. The signal wire from the ECM should be removed. Connect the signal wire to one end of the jumper wire. Connect the jumper wire's other end to the optimistic probe's edge. Connect the negative probe to stable chassis ground. Connect the negative probe to the chassis ground with a jumper and alligator clips if necessary.

 

To test DC volts, switch the electric voltmeter. Turn the key switch to "On". Ideally, the voltage should be about 0 volts. Slowly rotate the magnet perpendicular to the sensor's front. When the magnet approaches the sensor, the voltage should rise, and as it moves away, the voltage should fall. There is a problem with the sensor or the sensor's connections if the voltage does not change.

 


Ⅸ FAQ

1. How does a Hall effect sensor work?

Using semiconductors (such as silicon), Hall effect sensors work by measuring the changing voltage when the device is placed in a magnetic field. In other words, once a Hall effect sensor detects that it is now in a magnetic field, it can sense the position of objects.

 

2. What triggers a Hall effect device?

Hall effect sensors are activated by a magnetic field and in many applications, the device can be operated by a single permanent magnet attached to a moving shaft or device. There are many different types of magnet movements, such as ‘Head-on’, ‘Sideways’, ‘Push-pull’ or ‘Push-push’ etc sensing movements.

 

3. What is the use of a hall effect sensor?

Hall effect sensors are commonly used to time the speed of wheels and shafts, such as for internal combustion engine ignition timing, tachometers and anti-lock braking systems. They are used in brushless DC electric motors to detect the position of the permanent magnet.

 

4. What is the principle of the Hall effect?

The Hall Effect principle states that when a current-carrying conductor or a semiconductor is introduced to a perpendicular magnetic field, a voltage can be measured at the right angle to the current path.

 

5. How sensitive is a Hall effect sensor?

These ratiometric devices have a sensitivity of 5 mV/gauss and 2.5 mV/ gauss, respectively, an operating temperature range of -40°C to +150°C, and are temperature compensated over their full operating range.

 

6. What is the difference between a Hall effect sensor and an inductive sensor?

Inductive sensors detect metallic objects and hall effect sensors detect the presence of a magnetic field.

 

7. What is the origin of the Hall effect?

The history of the Hall effect begins in 1879 when Edwin H. Hall discovered that a small transverse voltage appeared across a current-carrying thin metal strip in an applied magnetic field.

 

8. How can you tell if a Hall sensor is bad?

Loss of power, loud noise and the feeling that the motor is somehow blocked are often signs that either the controller is dead or that you may have issues with the hall sensors inside the motor.

 

9. What is inside a Hall effect sensor?

The Hall effect sensor is a thin sliver of semiconductor material just like the chip inside a micro or RAM devise. It works on the electromagnetism principle. When you move a magnet close enough to the sensor generates a small voltage. This goes to an amplifier which boosts the voltage high enough to be used by other electronic devices.

 

The best example is the wheel speed sensor. A small magnet is attached to the inside of a car wheel. Every time the magnet moves past the sensor that is one rotation of the wheel. The information is passed to the speedometer and odometer unit where it is displayed to the driver.

 

10. What is a hall effect sensor for on a vehicle?

A hall effect sensor operates by a magnetic field and can also be referred to as a crank position sensor. It checks the crankshaft position for the engine to fire the spark plugs. If it is bad, the engine might stall and would not start without the signal from the Hall effect sensor.

 

Hall effect sensors can also be used to determine speed, distance, or engine crankshaft position and camshaft position. All hall effect sensors have different electronics internally with different program measurements and are not interchangeable.

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