In electronics, sensors are components that take inputs from events occurring in the verisimilitude world and convert them into outputs that can be interpreted abstractly by microcontrollers, development boards, computers, etc. Sensors are the most prominent part of an electronics project specifically designed to discern probabilities. Any processor without outputs transferred by sensors, although developed flawlessly for detecting, cannot detect actions to evaluate nor make predictions. Overtly, due to sensors’ significance, there are umpteen sensors with unique abilities, categorized in different types and groups.
Sensors can be categorized in various ways according to requirements and the point of view while classifying them. However, in this article, I will talk about the three main classification methods applied to sensors. The first classification method prioritizes whether sensors utilize an external power source while working in a circuit. In this method, if a sensor requires an external power to adjust its resistance or voltage depending on inputs from the environment, the sensor is categorized under active sensors (components). In other words, an active sensor needs a power supply to generate outputs. For instance, many semiconductors are classified under active sensors. A semiconductor diode consists of the juxtaposition of a layer of n-type and a layer of a p-type semiconductor, called a p-n junction. If you connect the n-type material to the negative terminal of a voltage source and the p-type to the positive terminal, the excess electrons from the n-type material will be repelled by the negative charge and flow into the p-type crystal. Conversely, if a sensor does not require an external power source to generate outputs, it is categorized under passive sensors (components). In other words, passive sensors cannot affect electricity in the circuit directly. For instance, resistors, capacitors, and inductors are categorized under passive sensors. As you can see, without passive sensors, an electronics project and circuit design would not be possible. We can say that passive and active sensors (components) are the building blocks of electronics. For example, the introduction of semiconductors had its greatest impact on computer technology. And, the first commercial computer built entirely with transistors appeared in 1957.
In the second classification method, sensors are categorized regarding in which field they detect qualities such as chemical sensors, physical sensors, biosensors, radioactive sensors, etc. These sensors mostly used in fabrication processes and laboratories to conduct experiments thoroughly. For instance, physical sensors measure a physical quantity, like temperature or humidity, and convert it into a signal which can be read by a processor. In this way, a processor gains the ability to perceive the real world in physical means as a living organism does. There are plenty of devices created with physical sensors that interpret real-world inputs in wearable electronics and robotics. As a sub-category, these sensors can be classified in regard to their conversion types: electrochemical, photoelectric, electromagnetic, biomedical, etc. In other words, in this sub-category, sensors collect inputs from one particular field, interpret that information, convert it into data meaningful in a different field. For instance, electrochemical sensors give information about the composition of a system in real-time by coupling a chemically selective layer to an electrochemical transducer, such as industrial gas detection systems utilized in mines.
In the third and final classification method, sensors are categorized depending on the output signal type they are producing – analog and digital. Digital sensors are able to detect only two possibilities while generating outputs – 1 or 0. In other words, they can only identify whether the experimenting condition is met or not – detected or not detected. For instance, a digital fire detection sensor can only produce true (1) as output when there is a fire or false (0) when there is not. Hence, digital sensors are impeccable for notification systems. On the other hand, analog sensors can detect variables in a range – from 0 to 100%. In that regard, they can generate outputs depending on the emerging level of the experimenting parameters – gas, temperature, magnetic field, etc. Analog sensors work, flawlessly, while conducting experiments to measure the current level of detecting events such as humidity in percentages. For example, a photoresistor detects the light density and generates outputs from 0 – no light – to 100% – when the maximum light density has been reached. So, it is able to measure the weather condition – cloudy, sunny, etc. – depending on the light density instead of merely detecting whether there is bright or dim like a digital sensor. Commonly, analog and digital sensors used by either makers and electronics enthusiasts to create DIY projects with development boards such as Arduino and Raspberry Pi or professionals to design low-cost projects. Also, they are the best option to implement on a PCB board design due to their flexibility and efficacy. Generally speaking, connecting sensors to microcontrollers to create electronics projects requires lots of wiring and soldering; nevertheless, you can get rid of all redundant wiring by designing PCBs (Printed circuit boards) for your electronics projects. Utilizing different sensor types in PCB designs, you can create heterogeneous devices and shields – for Arduino, Raspberry Pi, etc. – with unique abilities and flexibility at low-cost. Furthermore, nowadays, you do not even need to be in the same place with all the mentioned sensor categories to observe the data produced by them: you can send the data to a server accessible in anywhere and with any device – smartphones, computers, or tablets – in the means of the internet of things (IoT).
In conclusion, the salience of sensors types is due to their ability to convert real-world perceptions into artificial variables that can be interpreted by processors without an impeding error in various fields.