What is an accelerometer?
An accelerometer is an electromechanical device that measures acceleration forces. These forces may be static, like the constant force of gravity pulling at your feet, or they could be dynamic – caused by moving or vibrating the accelerometer.
How do accelerometers work?
There are many different ways to make an accelerometer! Some accelerometers use the piezoelectric effect – they contain microscopic crystal structures that get stressed by accelerative forces, which causes a voltage to be generated.
Another way to do it is by sensing changes in capacitance. If you have two microstructures next to each other, they have a certain capacitance between them. If an accelerative force moves one of the structures, then the capacitance will change. Add some circuitry to convert from capacitance to voltage, and you will get an accelerometer.
There are even more methods, including use of the piezoresistive effect, hot air bubbles, and light.
What are accelerometers useful for?
Accelerometers have many uses in industry and science:
Highly sensitive accelerometers are used in inertial navigation systems for aircraft and missiles.
They are used in tablet computers and digital cameras so that images on screens are always displayed upright.
In unmanned aerial vehicles, accelerometers help to stabilise flight.
Vibration in rotating machines is monitored by accelerometers.
In the computing world, IBM and Apple are using accelerometers in their laptops to protect hard drives from damage. If you accidentally drop the laptop, the accelerometer detects the sudden freefall, and switches the hard drive off so the heads don’t crash on the platters.
In a similar fashion, high g accelerometers are the industry standard way of detecting car crashes and deploying airbags at just the right time. In the event of a crash, the crash sensor (an accelerometer) sends a signal to the airbag control unit. This control unit triggers the inflation device, which generates nitrogen gas by igniting a mixture of sodium azide (NaN3) and potassium nitrate (KNO3).
By measuring the amount of static acceleration due to gravity, you can find out the angle the device is tilted at with respect to the earth. By sensing the amount of dynamic acceleration, you can analyze the way the device is moving.
PRACTICE QUESTIONS
QUES . Consider the following actions: UPSC PRELIMS 2023
1 . Detection of car crash/collision which results in the deployment of airbags almost instantaneously
2 . Detection of accidental free fall of a laptop towards the ground which results in the immediate turning
off of the hard drive
3 . Detection of the tilt of the smartphone which results in the rotation of display between portrait and
landscape mode
In how many of the above actions is the function of accelerometer required?
(a) Only one
(b) Only two
(c) All three
(d) None
Ans (c)
