What is an accelerometer?
An accelerometer is an electromechanical device that measures acceleration forces. These forces can be static, like the constant force of gravity pulling on your feet, or they can be dynamic – caused by the movement or vibration of the accelerometer.
What are accelerometers for?
By measuring the amount of static acceleration due to gravity, you can find out the angle at which the device is tilted relative to the Earth. By feeling the amount of dynamic acceleration, you can analyze the way the device is moving. At first, measuring tilt and acceleration doesn't seem all that exciting. However, engineers have discovered many ways to create really useful products with them.
An accelerometer can help your project better understand its environment. Are you driving uphill? Will he fall when he takes another step? Is he flying horizontally or is he bombing his teacher? A good programmer can write code to answer all of these questions using the data provided by an accelerometer. An accelerometer can help analyze car engine problems using vibration tests, or you can even use one to make a musical instrument.
In the computing world, IBM and Apple have recently started using accelerometers in their laptops to protect hard drives from damage. If you accidentally drop your laptop, the accelerometer detects the sudden free fall and shuts down the hard drive so the heads don't hit the platters. Similarly, high-g accelerometers are the industry standard way of detecting car accidents and deploying airbags at the right time.
WHAT ARE THE DIFFERENT TYPES OF ACCELEROMETER?
There are many different types of accelerometers and each has unique features, advantages and disadvantages. The different types include:
Different technologies
- Piezoelectric accelerometers
- Piezoresistive accelerometers
- Strain gauge-based accelerometers
Different output accelerometers
- Load output
- Voltage output (3 wires)
- Output 4-20mA
- Speed output accelerometers
Different accelerometer designs
- Shear type design
- Single-ended compression design
- Isolated compression
- Inverted compression
- Flexible design
How do accelerometers work?
There are many different ways to make an accelerometer! Some accelerometers use the piezoelectric effect – they contain microscopic crystalline structures that are strained by accelerative forces, which causes a voltage to be generated. Another way to do this is by detecting changes in capacitance. If you have two microstructures next to each other, they will have a certain capacitance between them. If an accelerating force moves one of the structures, the capacitance will change. Add some circuitry to convert capacitance to voltage and you get an accelerometer. There are even more methods, including using the piezoresistive effect, hot air bubbles, and light.
Benefits:
- Available in various designs (such as compression, shear and extensometer), sizes, weights and mounting arrangements (such as center, pin, screw mounting and gluing). Ease of installation is also an advantage.
- Accelerometers are available for high temperature environments
(up to 1,200”F). - Broadband frequency and amplitude response.
- Accelerators are available for high and low frequency. Rugged, durable construction and long-term reliability. frequency measurement capabilities (up to DC).
Disadvantages:
- Requires contact (mounting) with the object being measured. Therefore, the mass of the accelerometer must be small relative to this object (generally it must be less than 5% of the mass of the vibrating component being measured).
- Mounting sensitive (must be mounted securely).
- Sensitive to cable noise and “whiplash” (change in cable capacitance caused by dynamic flexing of the cable).
- The results are not particularly reliable when the displacement is calculated by (electronically) double integration of the acceleration signal.
ACCELEROMETER APPLICATIONS
Accelerometers are one of those sensors that find countless applications in academia as well as a large number of industries. These applications range from airbag sensors in automotive applications to vibration monitoring in bridges and many military and space systems. There are several practical applications for accelerometers; Accelerometers are used to measure static acceleration (gravity), tilt of an object, dynamic acceleration, shock to an object, speed, and vibration of an object. Accelerometers are being used nowadays in mobile phones, laptops, washing machines, etc.
