What Is an Accelerometer?
An accelerometer is a device that measures acceleration, the rate of change of speed per unit of time.
Accelerometers can measure the acceleration of a vehicle or the vibration of a machine. They can also collect and store information on vibration and tilt.
Accelerometers are divided into four main types: piezoelectric, servo, strain gauge, and semiconductor.
Uses of Accelerometers
Accelerometers are used in a wide range of fields, including the automotive, processing, and electronics industries. In the automotive industry, they are used for engine testing. In addition to this, they are often installed for automobile research and development and abnormality detection.
When used as vibration meters, they are installed to monitor abnormal vibrations in rotating equipment. Sudden failure of rotating equipment directly leads to increased costs, so vibration monitoring prevents equipment failure before it occurs.
Accelerometers are also used in large industrial equipment for quality control of products in transit.
Accelerometers have long been used as vibration meters for vibration measurement and testing. In recent years, accelerometers have been built into smartphones and used in pedometers and health care applications.
Principle of Accelerometers
The principles of how accelerometers can measure vibration and acceleration vary depending on the type of accelerometer.
1. Piezoelectric Accelerometer
The piezoelectric element inside the sensor expands and contracts under the pressure caused by acceleration and releases an electric charge to detect acceleration.
2. Servo Type Accelerometer
Consists of a coil, magnet, and pendulum. The movement of the pendulum caused by acceleration generates electricity in the coil, and the amount of electricity generated is measured and converted to acceleration.
3. Strain Gauge Type Accelerometer
Strain is generated by the inertial force on the internal weight due to acceleration, and the amount of strain is detected by the gauge to measure acceleration.
4. Semiconductor Type Accelerometer
A capacitor consisting of movable electrodes is incorporated inside a semiconductor. Acceleration is measured when the capacitance of the capacitor changes due to the bending of the movable electrodes caused by acceleration.
How to Fix Accelerometers
The method of mounting an accelerometer has a significant impact on the accuracy of the measurement. There are five major methods of securing acceleration sensors.
1. Screw Fixation
This is the most ideal method. To increase rigidity, a thin layer of grease is applied to the object to be measured and then tightened to the specified torque.
2. Cementing Agent Clamping
Apply the cementing agent to the object to be measured and fix it.
3. Insulating Washer Fixing
Used to insulate the object to be measured from the sensor.
4. Fixing Magnet
Used as a simple fixing method when the object to be measured is magnetic.
5. Hand Probe Fixing
This is used when it is not possible to fix the probe with screws, or when a quick inspection is required. Fix the cable so that no excessive force is applied to the connection part of the accelerometer.
Other Information on Accelerometers
Measuring Vibration With Accelerometers
Vibration is measured from three parameters: displacement, velocity, and acceleration. Accelerometers are used as one of the sensors for measurement. Among vibration sensors, piezoelectric accelerometers are characterized by their ability to cover a wide frequency range.
The definition of mechanical vibration is defined as “a temporal change in the magnitude of a quantity representing the motion or displacement of a mechanical system that alternately repeats a state in which it is greater than or less than a certain average or reference value.”
Frequency analysis is widely used to analyze vibration. It is a method to determine what frequencies and how much intensity each of the measured waveforms contains.