Accelerometer
An accelerometer is a
sensing element that measures acceleration; acceleration is the rate of change
of velocity with respect to time. It is a vector that has magnitude and
direction. Accelerometers measure in units of g – a g is the acceleration
measurement for gravity which is equal
to 9.81m/s². Accelerometers have developed from a simple water tube with an air
bubble that showed the direction of the
acceleration to an integrated circuit that can be placed on a circuit board. Accelerometers can measure:
vibrations, shocks, tilt, impacts and motion of an object.
Types of Accelerometers
There are a number of
types of accelerometers. What differentiates the types is the sensing element
and the principles of their operation.
Capacitive
accelerometers sense a change in electrical capacitance, with respect to
acceleration. The accelerometer senses the capacitance change between a static
condition and the dynamic state.
Piezoelectric
accelerometers use materials such as crystals, which generate electric
potential from an applied stress. This is known as the piezoelectric effect. As
stress is applied, such as acceleration, an electrical charge is created.
Piezoresistive
accelerometers (strain gauge accelerometers) work by measuring the electrical
resistance of a material when mechanical stress is applied
Hall
Effect accelerometers measure voltage variations stemming
from a change in the magnetic field around the accelerometer.
Magnetoresistive
accelerometers
work by measuring changes in resistance due to a magnetic field. The structure
and function is similar to a Hall Effect accelerometer except that instead of
measuring voltage, the magnetoresistive accelerometer measures resistance.
Heat
transfer accelerometers measure internal changes in heat transfer
due to acceleration. A single heat source is centered in a substrate and
suspended across a cavity. Thermoresistors are spaced equally on all four sides
of the suspended heat source. Under zero acceleration the heat gradient will be
symmetrical. Acceleration in any direction causes the heat gradient to become
asymmetrical due to convection heat transfer.
MEMS-Based Accelerometers
MEMS (Micro-Electro
Mechanical System) technology is based on a number of tools and methodologies,
which are used to form small structures with dimensions in the micrometer scale
(one millionth of a meter). This technology is now being utilized to
manufacture state of the art MEMS-Based Accelerometers.
![Angular versus linear motion. Angular versus linear motion.](https://www.maximintegrated.com/en/images/appnotes/5830/5830Fig01.png)
Future Accelerometer Advancements
In the next decade,
NANO technology will create new applications and dramatically reshape this area
of technology.
Applications for Accelerometer
From industry to
education, accelerometers have numerous applications. These applications range
from triggering airbag deployments to the monitoring of nuclear reactors. There
are a number of practical applications for accelerometers; accelerometers are
used to measure static acceleration (gravity), tilt of an object, dynamic
acceleration, shock to an object, velocity, orientation and the vibration of an
object. Accelerometers are becoming more and more ubiquitous: cell phones,
computers and washing machines now contain accelerometers.
Other practical
applications include:
• Measuring the
performance of an automobile
• Measuring the
vibration of a machine
• Measuring the motions
of a bridge
• Measuring how a
package has been handled
Digital accelerometers will give you information using a
serial protocol like I2C, SPI or USART, while analog accelerometers will output
a voltage level within a predefined range that you have to convert to a digital
value using an ADC (analog to digital converter) module.
The digital accelerometer is more sophisticated than the
analog. Here the amount of high voltage time is proportional to the
acceleration. One of its major advantages is that it is more stable and
produces a direct output signal. Accelerometers are now also used in aerospace
and many military applications, such as missile launch, weapon fire system, rocket
deployment etc. Many a times these accelerometers are used to protect fragile
equipment during cargo transportation, and report any strain that might cause a
possible damage. Some companies have also managed to develop a wireless 3-axis
accelerometers which are not only low in cost but are also shock durable. This
3-axis accelerometer has sensors that are used to protect mobiles and music
players. Also these sensors are used in some of the devices used for traffic
navigation.
![Image result for accelerometer](https://images-na.ssl-images-amazon.com/images/I/51B5LYwVYOL._SY355_.jpg)
Accelerometer
is consist of five six pins and we use five pins for our
requirement. These five pins are
1)+vcc
2)Gnd
3) x-axis
4) y-axis
5)z-axis
We connect
++vcc to five volts, and another one is for ground. The remaning pins are
connected to the adc channels of microcontroller. The output
from accelerometer is anlog value and we converting these values to
digital.
By
tilting the accelerometer device we can find the values that are to be changing
in accordance with accelerometer tilting.
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