IOT – Sensor and Actuator

                                                  Sensors –

Sensors – Let’s start with the proper definition of sensors first, devices that detect and responds to some type of input from the physical environment. Output is generally a signal that is converted to human-readable display at the sensor location or transmitted electronically over a network for reading or further processing.

Actuators – Can be type of motors which is responsible for moving or controlling a mechanism or system. Sensors will sense the measured property and basis of that action can be performed with the help of actuators.  Types of Actuator – Hydraulic, Pneumatic, Electric and Mechanical.

Sensors have been in existence into this world since ages like thermometer for monitoring human temperature and weighing scale for monitoring weight of the equipment but today Sensors are using very predominantly in various applications like touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base, besides innumerable applications of which most people are never aware. There are two types of Sensors e.g Digital Sensors or Analog Sensors. Digital sensors are mainly used in water, waste water and industrial processes, they measure parameters such as pH, redox potential, and conductivity. A digital sensor system also consists of the sensor itself, a cable, and a transmitter. The differences to analog sensor systems are:

  1. a) The sensor has an electronic chip. The measuring signal is directly converted into a digital signal inside the sensor. The data transmission through the cable is also digital. This digital data transmission is not sensitive to cable length, cable resistance or impedance, and is not influenced by electromagnetic noise.
  2. b) The connection between sensor and cable can be contact less and done by inductive coupling. Humidity and related corrosion is no longer an issue.

Sensors properties –

Sensors Range – Define the Maximum and Minimum output signal values of the measured property.

  • BIAS – If the output signal is not zero when the measured property is zero, the sensor has an offset or bias. This is defined as the output of the sensor at zero input.


  • Non Linearity – If the sensitivity is not constant over the range of the sensor, this is called non linearity. Usually this is defined by the amount the output differs from ideal behavior over the full range of the sensor, often noted as a percentage of the full range.
  • Dynamic Error – deviation is caused by a rapid change of the measured property over time, there is a dynamic error.
  • Drift – Indicates a slow degradation of sensor properties over a long period of time.
  • Noise – is a random deviation of the signal that varies in time.

Passive Sensors vs. Active Sensors

Passive sensors react to signals, such as sound waves or heat spikes. e.g – Photographic, thermal, electric filed sensing, chemical, infrared and seismic

Active Sensors emit signals that are reflected back to the sensor. E.g – microscopes, LIDAR, radar, GPS, x-ray, sonar, infrared and seismic.

Ultrasonic Sensors – These are active Sensors that emit ultrasonic ( High Speed) waves that reflect off object. An object in motion will reflect faster because the distance between the detector and the object is shorter.

Passive- Infrared Sensors – A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. PIR sensors allow you to sense motion, almost always used to detect whether a human has moved in or out of the sensors range.

PIR Sensor


Electric Current Sensor – is a device that detect electric current (AC or DC) in a wire, and generate a signal proportional to it. Signal could be analog voltage or current or even digital output.

Electric Current sensor

MEMS – Micro-Electro Mechanical system is a technique of combining electrical and mechanical components together on a single CHIP, to produce a system of miniature dimensions. It’s a unique sensor portfolio, from discrete to fully-integrated solutions, to fulfill every design need. While the functional elements of MEMS are miniaturized structures, sensors, actuators, and microelectronics, the most notable (and perhaps most interesting) elements are the micro sensors and micro actuators.



Gyroscope Sensors – That measures the angel or maintain the rate of rotation. They are small in size, inexpensive sensors that measures angular velocity. Application e.g – Used in Anti-Skid control, Antenna stabilization and gaming applications.



Accelerometer Sensor – Accelerometer are the devices that measures acceleration, which is the rate of change of the velocity of an object. They measures in meters per second square ( m/s2) or in G-force. Accelerometer are useful for sensing vibrations in system or for orientation application. Accelerometer are electromechanical devices that sense either static or dynamic forces of acceleration.


Magnetic Sensor – Are used the changes in magnetic field for their operations. Sensors used to measure the current, speed, position and displacement. On the bases of sensing the variation of magnetic fields, magnetic sensors are of three types.

Low field sensors – Can sense very low volume of magnetic fields, less than 1uG

Earth field sensors – The magnetic range for the medium field sensors lends 1uGauss to 10uGauss.



Communication Interface – First of all the sensors required basic connections for operations are power and connection interfaces. All Sensors have different types of communication interfaces like- Analog or digital, but many sensors have both the interfaces for communication. Ideally uses digital sensors while making any application because these tend to have more functionality and be less susceptible to noise than analogy sensor. Digital interfaces can either communicate over SPI or I2C communication protocol and MEMS uses integrated circuits interfaces for communication.


Types of Sensors –



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