Accelerometers sensor

Accelerometer

An accelerometer is an electro- mechanical device that measures proper 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 and vibrating the accelerometer.

Principle

The working principle of an accelerometer is based on PIEZO-ELECTRIC EFFECT (due to accelerative forces) and on the DISPLACEMENT SENSING (based on displacement of mass).

How it works

In most of the cases working of an ACCELEROMETER is based on voltage generation and its further calculations which leads to the determination of acceleration where as some other involve the measurement of displacement of mass.

Types of accelerometer

There are basically two types of accelerometer frequently used for measurement of acceleration

Piezo electric accelerometer

Displacement sensing or seismic type accelerometer

Piezo -Electric type

It employs the piezo electric effect of certain materials to measure dynamic changes. It converts one form of energy into another and provide electrical signal of measured amount.

Working Principle

The working principle of this is based on “NEWTONS THIRD LAW” . The force exerted on the material can be observed in the change in the electrostatic force or voltage generated by the piezoelectric material.

Fastened on the base which act as a spring and squeezes the mass against crystal for acceleration determination.

Leads to voltage generation and fluctuation in voltage leads to measurement of imposed acceleration.

Sensor consist of piezoelectric crystal sand witched between two electrodes with a mass placed on it

Advantages

Rugged and Inexpensive
High Impedance
High sensitivity
High frequency response

Disadvantages

Sensitive to temperature
Hysteresis error
Less longevity
Decreased efficiency with time

Seismic accelerometer

In displacement sensing accelerometer the displacement of a mass resulting from an applied force is measured and correlated to the acceleration .Here a common spring – mass-damper system which accomplishes the task of acceleration measurement through displacement.

Working Principle

The working principle of this is based on mass-spring-damper combination and similarly acceleration calculation from displacement.

The mass is supported by a spring and connected to the housing frame which is attached to a machine.

Relative mass movement is sensed and indicated by an electrical displacement transducer.

Correspondingly displacement and velocity are measured and further acceleration are measured.

Advantages

Easy Calculation
Simple and reliable
Durable and efficient

Disadvantages

Spring system is not always accurate
Fluctuation in mass leads to wrong calculation.

Application of Accelerometer

Acceleration and vibration calculation in vehicles
In industries for monitoring machines
Building and structural monitoring
Medical application and navigation
Transport