Physics

What is Accelerometer?

Last Update: February 15, 2023.

| Overview | Uses of accelerometer | Types of accelerometer |

1. Overview:

The accelerometer is a device that measures acceleration forces using electromechanical means. Such forces might be static, such as gravity, or dynamic, such as in the case of mobile gadgets. An accelerometer is a big electronic device that consists of a primary circuit. The accelerometer consists of various components, although its a humble look, and functions in a variety of ways.

An accelerometer is a device that measures how fast an object is moving. The acceleration (rate of change of velocity) of a body in its immediate rest frame defines proper acceleration. This is not to be confused with coordinate acceleration, which refers to movement in a specific coordinate system. An accelerometer at rest on the Earth’s surface, for example, will measure an acceleration owing to Earth’s gravity of g 9.81 m/s2 straight upwards (by definition). Accelerometers in free fall (falling into the core of the Earth at a rate of around 9.81 m/s2), on the other hand, will read zero.

Accelerometers have a wide range of applications in industry and science. Inertial navigation systems for airplanes utilize extremely sensitive accelerometers. Accelerometers measure vibration in rotating equipment. Accelerometers use in mobile, tablet computers, and digital cameras, and they keep images on screens upright. The accelerometer is used in the stabilization of unmanned aerial vehicles.

When two or more accelerometers are synced, they can track changes in suitable acceleration, namely gravity, over time and space—the gravitational field gradient. Gravity gradiometry is significant. Absolute gravity is a weak force that is strongly impacted by the Earth’s local density, which varies greatly.

2. Uses of accelerometer:

The accelerometer is used in different fields of industries. Here some uses of the accelerometer are:

2.1. Engineering:

Accelerometers measure the vehicle’s acceleration. Vehicles, equipment, buildings, process control systems, and security systems can all benefit from accelerometers. With or without the impact of gravity, accelerometers use to assess seismic activity, inclination, machine vibration, dynamic distance, and speed. The gravimeters use accelerometers that measure gravity. Gravimeters also accelerometers have been specifically built for use in gravimeters.

2.2. Biology:

Accelerometers are also becoming more used in biological research. While animals are out of sight, high-frequency recordings of bi-axial or tri-axial acceleration allow behavioral patterns to be detected. Furthermore, researchers can use acceleration recordings to determine the pace at which an animal expends energy in the wild, using methods such as limb-stroke frequency or overall dynamic body acceleration.

Due to the impossibility to study creatures in the wild using visual observations, such approaches have primarily been used by marine scientists; nevertheless, a growing number of terrestrial biologists are adopting comparable tactics.

2.3. Industry:

Accelerometers are also used in health monitoring to indicate shaft vibration. Its variations in time at the bearings of rotating equipment such as turbines, pumps, fans, rollers, and compressors, as well as bearing faults that, if not addressed promptly, can result in costly repairs. The user can monitor machinery and discover issues using accelerometer vibration data before the spinning equipment breaks altogether.

2.4. Medical applications:

However, Several companies develop and sold sports watches for runners that feature footpads with accelerometers to help determine the speed and distance of the runner wearing the device in recent years.

In Belgium, the government promotes accelerometer-based step counts to urge people to walk a few thousand steps each day.

In physical training, the Herman Digital Trainer uses accelerometers to quantify striking power.

It recommends that accelerometers be built into football helmets to measure the impact of head hits.

An inertial navigation system is a navigational device that employs a computer and motion sensors (accelerometers) to calculate the location, orientation, and velocity (direction and speed of travel) of a moving object constantly using dead reckoning without the use of external references. Inertial navigation systems or closely comparable technologies call as inertial guiding systems, inertial reference platforms, and a variety of other titles.

An accelerometer alone is inappropriate for determining changes in altitude over long distances where gravity significantly reduce vertically, such as in aircraft and rockets. The calibration and data reduction procedure is numerically unstable in the presence of a gravitational gradient.

2.6. Gravimetry:

A gravimeter, sometimes known as a gradiometer, is a gravimetric apparatus that measures the local gravitational field. Gravimeters are similar to accelerometers in that they are subject to all types of vibrations, including noise, that creates oscillatory accelerations. Integral vibration isolation and signal processing in the gravimeter counteract this.

3. Types of accelerometer:

There are different types of accelerometers:

3.1. Piezoelectric accelerometer:

The piezoelectric effect is the most well-known, and it works by stressing small crystal formations due to accelerative forces. The stress causes a voltage in the crystals, which the accelerometer converts to velocity and orientation.

A piezoelectric accelerometer measures dynamic changes in mechanical parameters such as mechanical stress, vibration, and acceleration by utilizing the piezoelectric effect of particular materials. Piezoelectric accelerometers, like other transducers, transform one kind of energy into another and respond with an electrical signal to the state, property, or amount. Acceleration turns a physical force into an electrical signal by acting on a seismic mass that maintains by a spring or hanging on a beam structure.

Although, high and low-impedance piezoelectric accelerometers are available. A charge amplifier or external impedance converter converts the charge output of a high-impedance accelerometer into a voltage. Minimal units employ the same piezoelectric sensing device as high-impedance units, a tiny built-in charge-to-voltage conversion, and an external power source coupler to energize the electronics and isolate the resulting DC bias voltage from the output signal.

A mass is connected to a piezoelectric crystal that is fixed on a casing in a piezoelectric accelerometer. Due to inertia, the mass of the crystal stays unchanged in space when the accelerometer body buzzes. The mass compresses and extends the piezoelectric crystal as a result. According to Newton’s second law, F = ma, this force is proportional to acceleration and produces a charge.

3.1.1 Benefits of Piezoelectric Accelerometer:

The advantages of piezoelectric accelerometers are as follows:

• High-frequency range
• No parts of the movement
• They have excellent linearity throughout their dynamic range.
• Minimum output noise
• Self-generating – no need for external power
• The velocity and movement can be calculated using the acceleration signal.

3.1.2. Uses of Piezoelectric accelerometer:

• The following are some of the most common uses for piezoelectric accelerometers:
• Combustion and dynamic stressing are two types of engine testing.
• Combustion, Explosion, and detonation are all examples of ballistics.
• Machine health monitoring, metal cutting, and industrial/factory machining equipment
• Transportation systems, rockets, machine tools, engines, flexible constructions, and shock/vibration testing are all examples of original equipment manufacturers.
• Transient response testing, stress, and vibration isolation, vehicle chassis structural testing, structural analysis, reactors, control systems, and materials evaluation are all examples of engineering.
• Ejection systems, rocketry, landing gear hydraulics, shock tube instrumentation, science lab, and dynamic testing are all aspects of aerospace.

3.2. Capacitance accelerometer:

The capacitance accelerometer detects the changes in capacitance between microstructures. The capacitance changes as the accelerative force move one of these microstructures, and the accelerometer converts this capacitance into voltage for understanding.

A vibration sensor is another name for a capacitive accelerometer.

The vibrations made on a device or surface are read and recorded by a capacitive accelerometer. It’s made up of an oscillator or any other fixed component that may store capacitance. The capacitive accelerometer’s native sensors detect the create capacitance or energy when these components move. The sensors connect with electrical circuitry that monitors the acceleration’s intensity and magnitude of the electrical current.

Airbag deployment sensors in autos, human-computer interface (HCI) devices, and cellophane are all examples of capacitive accelerometers in computational and commercial applications.