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 which 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 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 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 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 broadly 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.

Example - Thermometer, calorimeter, temperature gauge

Chemical

Chemical sensors measure the concentration of chemicals in a system. When subjected to a mix of chemicals, chemical sensors are typically selective for a target type of chemical (for example, a CO2 sensor senses only carbon dioxide).

Biosensors

Biosensors detect various biological elements such as organisms, tissues, cells, enzymes, antibodies, and nucleic acids.

Example - Blood glucose biosensor, pulse oximetery, electrocardiograph
    Factors Driving Adopting Sensors Within IoT

    There are three primary factors driving the adoption of sensor technology i.e. price, capability, and size.

    Cheaper sensors

    The price of sensors has consistently fallen over the past several years, and these price declines are expected to continue into the future. Sensors vary widely in price, but many are now cheap enough to support broad business applications.

    Smarter Sensors

    Sensor does not function by itself—it is a part of a larger system that comprises microprocessors, modem chips, power sources, and other related devices. Over the last two decades, microprocessors’ computational power has improved, doubling every three years

    Smaller Sensors

    There has been a rapid growth in the use of smaller sensors that can be embedded in smartphones and wearables. Micro-electro-mechanical systems (MEMS) sensors—small devices that combine digital electronics and mechanical components—have the potential to drive wider IoT applications.
    Generic Factor To Determine The Suitability Of Sensors

    There are, however, several generic factors that determine the suitability of a sensor for a specific application.


    Any of these factors can impact the reliability of the data received and therefore the value of the data itself.
    1. Accuracy - A measure of how precisely a sensor reports the signal.

    2. Repeatability - A sensor’s performance in consistently reporting the same response when subjected to the same input under constant environmental conditions.

    3. Range - The band of input signals within which a sensor can perform accurately. Input signals beyond the range lead to inaccurate output signals and potential damage to sensors.

    4. Noise - The fluctuations in the output signal resulting from the sensor or the external environment.

    5. Resolution - The smallest incremental change in the input signal that the sensor requires to sense and report a change in the change in the output signal.

    6. Selectivity - The sensor’s ability to selectively sense and report a signal.

    Sensor Connectivity

    The connectivity requirements of different types of IoT networks vary widely, depending on their purpose and resource constraints. A range of different wireless and wireline technologies can be used to provide full IoT connectivity.

    IoT devices communicate using a range of different communication protocols, which may include: short-range radio protocols (such as ZigBee, Bluetooth and Wi-Fi); mobile networks; or longer-rangeradio protocols (such as LoRa). These technologies can be segmented based on wireless versus wireline, and the wireless technologies can be grouped by personal area network (WPAN), wireless local area network (WLAN) or wide area network (WWAN) technologies.



    Comparing IoT Sensor Connectivity Technologies

    Each technology has distinct characteristics, including the range of their signal, the extent of their data, Throughput (or bandwidth), and the power needs of the communications device (or battery life), among other attributes.
     
     Personal Area Network
    ANT + Bluetooth + RFID
    + NFC 802.11.4 + ZigBee
    Local Area Networks
    (/WLAN)+ WiFi
    Wide Area
    Network(WWAN)
    Wireline
    (Copper/DSL/Ethernet/
    Coxial/Fiber
    Range
    ShortIntermediate Long Long
    BandwidthNarrowBroad Intermediate/Broad Intermediate
    Battery LifeLongShort Intermediate Short