Internet Of Things (IoT) Sensors And Connectivity

Introduction

Much of the functionality of IoT, and the data transmitted in the M2M and M2P notions of the IoT, are determined by the nature of sensor measurement. The other machines associated with IoT include actuators, the devices that can be directed to perform a physical activity such as opening an irrigation dam or closing a livestock fence. However, in the context of development, the majority of current applications utilize connected sensors.

Sensors are one of the primary modes of realizing the full potential of value-added to the companies, communities, and individuals who employ them for IoT purposes. In general, sensors host a heterogeneous school of functions. They can detect everything, from changes in temperature and humidity to the amount of force and pressure being simultaneously applied to thousands of products on a manufacturing floor. Sensors can be broadly deployed to overcome a host of challenges but in some cases, they may need to be highly customized. It is this customization that enables sensors to provide real added value for IoT and ICT4D initiatives.

Range Of Common Sensors

The below figure illustrates some commonly found sensors available in the commercial market.

Types of Sensors

Sensors are often categorized based on their power sources: active v/s passive.

Active sensors emit energy of their own and then sense the response of the environment to that energy. Radio Detection and Ranging (RADAR) is an example of active sensing.

Passive sensors simply receive energy (in any form) that is produced external to the sensing device. A standard camera is embedded with a passive sensor - it receives signals in the form of light and captures them on a storage device.

Position Sensors

Position sensor measures the position of an object; the position measurement can either be in absolute terms (absolute position sensor) or in relative terms (displacement sensor). Position sensors can be linear, angular, or multi-axis.

Example - Potentiometer, inclinometer, proximity sensor

Occupancy and Motion Sensors

Occupancy sensors detect the presence of people and animals in a surveillance area, while the motion sensors detect the movement of people and objects. The difference between the two is that occupancy sensors will generate a signal even when a person is stationary, while a motion sensor won't.

Example - Electric eye, RADAR

Velocity and Acceleration Sensors

Velocity (speed of motion) sensors may be linear or angular, indicating how fast an object moves along a straight line or how fast it rotates. Acceleration sensors measure changes in velocity.

Example - Accelerometer, gyroscope

Force

Force sensors detect whether a physical force is applied and whether the magnitude of the force is beyond a threshold.

Example - Force gauge, viscometer, tactile sensor (touch sensor)

Pressure

Pressure sensors are related to force sensors and measure the force applied by liquids or gases. Pressure is measured in terms of force per unit area.

Example - Barometer, bourdon gauge, piezometer

Flow

Flow sensors detect the rate of fluid flow. They measure the volume (mass flow) or rate (flow velocity) of fluid that has passed through a system in a given period of time.

Example Anemometer, mass flow sensor, water meter

Acoustic

Acoustic sensors measure sound levels and convert that information into digital or analog data signals.

Example - Microphone, geophone, hydrophone

Humidity

Humidity sensors-detect humidity (amount of water vapor) in the air or a mass. Humidity levels can be measured in various ways: absolute humidity, relative humidity, mass ratio, and so on

Example - Hygrometer, humistor, soil moisture sensor

Light

Light sensors detect the presence of light (visible or invisible).

Example - Infrared sensor, photodetector, flame detector

Radiation

Radiation sensors detect radiations in the environment. Radiation can be sensed by scintillating or ionization detection.

Example - Geiger–Müller counter, scintillator, neutron detector

Temperature

Temperature sensors measure the amount of heat or cold that is present in a system. They can be broad of two types: contact and non-contact. Contact temperature sensors need to be in physical contact with the object being sensed. Non-contact sensors do not need physical contact, as they measure temperature through convection and radiation.