What are accelerometer sensors? Explain how they work, what they measure, and how they are used

What are accelerometer sensors (acceleration sensors)

What are accelerometer sensors? Explanation of meaning and definition

Accelerometer sensors are inertial sensors that measures the change in velocity (acceleration) of an object over time. They are used in a variety of applications, including automobiles, smartphones, aircraft, industrial robots, and wearable devices.

Specifically, they can detect the following.

Types of accelerometer sensors

Accelerometers come in various types. Below is an explanation of the common types of accelerometers:

Piezoresistive type

These accelerometers are based on MEMS technology, enabling mass production at a low cost. They find extensive use in applications like gaming consoles and mobile phones.

Servo type

Servo accelerometers excel in low-frequency phase characteristics and are commonly used for seismic observation and structural monitoring.

Piezoelectric type

These accelerometers are suitable for high-frequency measurements and high acceleration (impact) detection. They are used in applications such as collision detection in automobiles and vibration measurement during drop tests.

Capacitive type

Capacitive accelerometers are ideal for low-acceleration measurements and are often employed in automotive body control systems due to their self-diagnostic capabilities.

Frequency-change type

These sensors detect acceleration by monitoring changes in the resonant frequency of the sensing element. Their high Q-factor fork structure ensures stability and high resolution, making them suitable for structural monitoring and seismographs.

Accelerometer sensors vs gyroscopes

Accelerometers and gyro sensors are both used to detect motion, but they measure different aspects.

Accelerometers

• Accelerometers measure linear acceleration experienced by an object.
• They detect acceleration when an object transitions between a stationary state and a moving state, or changes direction or speed.
• Specifically, they can detect the following:
  • Tilt
  • Vibration
  • Impact

Gyro sensors

• Gyro sensors measure the rotational speed of an object.
• Also known as "angular velocity sensors, they detect changes in the rotation angle per unit time.
• This allows them to sense rotation direction, angle, and vibration.
• They are used for:
  • Rotational vibration detection
  • Compensation for hand tremors
  • Attitude control

In summary, the difference between accelerometers and gyro sensors lies in the type of motion they measure. Accelerometers focus on linear acceleration, while gyro sensors measure rotational speed.

Accelerometer sensors vs Vibration sensors

Accelerometers and vibration sensors are both inertial sensors used to detect motion, but they serve different purposes.

Accelerometers

• Accelerometers measure linear acceleration experienced by an object.
• Acceleration is the rate of change of velocity and is expressed in m/s².
• They can detect the following:
  • Tilt
  • Vibration
  • Impact

Vibration sensors

• Vibration sensors detect an object's vibrations.
• Vibration refers to periodic motion of an object.
• Vibration magnitude is expressed in amplitude (mm) and frequency (Hz).
• They can detect:
  • Machinery vibrations
  • Earthquakes
  • Impacts

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Accelerometer sensors how do they work

How accelerometers work and working principle

The following describes the operating principle of accelerometers.

Operating principle of accelerometers

Accelerometers measure acceleration using principles such as piezoelectric elements or changes in resonant frequency. The operating principle is commonly explained by visualizing a mass connected to a spring. When the mass moves, it causes stretching or compression in the piezoelectric or resonant element, resulting in an electrical charge or change in frequency. Detecting these position or vibration changes allows us to derive the object's acceleration. (Note: An illustration of the mass connected to a spring would enhance understanding.)

Accelerometer axes

Accelerometers have the concept of "axes." For example, a 3-axis accelerometer can measure acceleration along the X, Y, and Z axes (directions). In simpler terms, it can measure acceleration in left-right, forward-backward, and up-down directions. 3-axis accelerometers are commonly used to understand an object's movement and tilt.

What do accelerometers measure

What do accelerometers do

Accelerometers are devices that measure the proper acceleration of an object. Proper acceleration refers to the acceleration (the rate of change of velocity) of the object relative to an observer who is in free fall (that is, relative to an inertial frame of reference). When an object transitions between a stationary state to a moving state, or changes direction or speed, the accelerometer detects this acceleration.
Common applications include screen rotation in smartphones, collision detection in automobiles, and vibration monitoring in structures. Specifically, accelerometers can detect the following:

Accelerometer sensors uses (accelerometer sensors applications)

Earthquake measurement using accelerometer sensors

Accelerometers play the following key roles in earthquake measurement and seismic monitoring:

Seismic measurement

• They measure the acceleration when an earthquake occurs, detecting the vibration of seismic waves.
• 3-axis accelerometers measure acceleration in the XYZ directions, providing information on the seismic motion.

Building monitoring:

• They monitor vibrations and displacements in buildings caused by earthquakes.
• By offering highly sensitive and accurate acceleration data, the building monitoring system can evaluate the structural integrity of buildings.

Disaster preparedness:

• To ensure appropriate responses during earthquakes, accelerometers are integrated into disaster planning applications and systems.

Structure monitor using accelerometer sensors

In addition to traditional visual inspections and tapping tests, monitoring using accelerometers has become widely adopted in recent years.

• Mechanism of Structural Monitoring Using Accelerometers
  Accelerometers are devices that measure the acceleration of an object. When installed on structures, accelerometers detect the vibrations and impacts experienced by the structure and convert this data into electrical signals.

These electrical signals can be recorded by data loggers and analyzed, allowing for the following capabilities:

• Specific Methods for Structural Monitoring Using Accelerometers
  These are methods for structural monitoring using accelerometers.

• Advantages of Structural Monitoring Using Accelerometers
  Using accelerometers for structural monitoring offers following several advantages

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Epson's accelerometer sensors

Overview and features of Epson's accelerometer sensors

Epson's accelerometers are high-performance sensing devices with the following features:

Crystal-based acceleration sensing element

• By forming a dual-tone oscillator and cantilever inside the sensor using quartz crystal, differences in thermal expansion coefficients between components are eliminated.
• This suppresses sensitivity changes due to temperature variations.
• Notably, it minimizes sensitivity fluctuations caused by temperature changes.

Digital approach

• Epson employs a digital measurement IP that eliminates analog circuits.
• Using a proprietary digital frequency detection method, it achieves high-precision, wide-bandwidth acceleration detection.

Sensor control from a PC

• Outputting digital data values allows sensor data processing in a PC environment.
• Through generic I/F boards or units, you can easily connect and build systems in a diverse choice of programming environments.

Low noise, high resolution, and stability

• Epson achieves noise performance below 1µG/rtHz with a wide detection range.
• These accelerometers provide high-precision data and exhibit excellent shock resistance.

Slim system configuration

• Their compact size eliminates the need for specialized PLC A/D units, reducing overall system costs.

Waterproof and dustproof units

• Waterproof units (with CAN interface) are also available, that are suitable for use in harsh environments.

Epson's accelerometer sensors technology

Epson's accelerometers utilize a frequency-change structure based on quartz microfabrication technology. While conventional accelerometers often employ Micro Electro Mechanical Systems (MEMS) with tiny mechanical structures, Epson has developed and manufactured sensors using its proprietary quartz processing technology.

Mechanism of quartz microfabrication technology

Epson's accelerometers, which utilize quartz microfabrication technology, measure acceleration through the following mechanism:

Inside the sensor, there are tiny structures called crystal oscillators and cantilevers.
When the sensor experiences acceleration, the cantilever bends, causing a change in the frequency of the crystal oscillator.
By measuring this frequency change, the acceleration is calculated and provided as the output.
Quartz oscillators exhibit characteristics that are less affected by temperature variations and aging, enabling high-precision and stable acceleration measurements.

Comparison with MEMS-based sensors

While MEMS-based accelerometers offer advantages such as compactness, light weight, and affordability, they are more susceptible to temperature change and aging effects. In contrast, Epson's quartz microfabrication technology results in accelerometers that are more accurate, stable, and capable of handling a wider range of applications.

How to use Epson's accelerometer sensors

The basic procedure for using Epson's A352 accelerometer (evaluated via PC connection) is as follows:

1. Attach the relay board to the sensor body.
2. Secure the sensor with the attached relay board to a metal plate (that is intended to be secured to a target object) using screws.
3. Connect the cable ends to the USB evaluation board and the relay board.
4. Connect a USB cable to the USB evaluation board.
5. Establish a connection between the sensor and the PC via the USB cable. Note: Always perform the sensor-to-PC connection as the last step. Reversing steps 4 and 5 may cause electrical damage to the circuit.
6. Analyze the data using PC software. You can collect acceleration sensor measurements and verify waveforms on a Windows PC using the Epson Vibration Logger. Additionally, the Epson Vibration Data Viewer allows waveform confirmation for acceleration data measured with the Epson Vibration Logger on a Windows PC. By examining waveform graphs, RMS values, and Fourier transform results, you can easily identify peak frequencies, aiding in pinpointing vibration sources.

Epson's A352 accelerometer maintains consistent sensitivity even at low frequencies, allowing it to detect vibrations from slow-moving objects. When measuring large motors or low-speed rotating machinery such as gearboxes, it can reveal details that may have been previously undetected.