Sensors

INTRODUCTION
          Sensors are devices which are used to detect and respond to certain physical actions. They are able to respond to physical parameters like Temperature, Humidity, Touch, Radiation, Speed etc... They convert these parameters to electrical signals which can be measured through devices. It is not an independent device and is always used with other devices. Just like Humans they can sense their environment and respond quickly. They are better than humans when it comes to sensitivity and responding. Some Sensors also affect what they measures like, a thermometer at room temperature when measuring a hot substance, cools it down and gets hotter. Although they are designed to have a small or no effect on the parameters which they measure. Latest Technology Sensors are manufactured at the microscopic scales and are much sensitive than macroscopic sensor. These are called Microsensors which are manufactured using MEMS ( Micro Electromechanical Systems) Technology. They are much faster and efficient when compared to macrosensors. With the advancements in micromachinery and other microscopic platforms the use of microsensors have expanded beyond the scientific fields to daily usage. Applications include machinery, airplanes, cars, smart phones, robotics,emergency alarms, security devices etc...

TYPES OF SENSORS
          There are many different types of sensors in our daily life, let us discuss some of them in brief and lets see how they works

• TEMPERATURE SENSORS 

          This type of sensors detects any type of change in temperature irrespective of its cause and converts it into a readable form. The best example is a thermometer which contains mercury which contracts and expands with the alterations in the temperature. The position of the mercury is observed by a viewer and the temperature at the level of mercury is observed through the graduations and readings on its outer glass. Another example is a Thermistor which is used in fire alarms. Thermistors are resistance thermometers whose resistance is dependent on temperature. Modern thermistors consist of a semi conducting material mostly a metal oxide. When the temperature increases charge carriers in a semiconductor increases and a signal is sent to a device monitoring it and the alarm rings indicating a sudden increase in temperature which can be a result of fire. Other examples include Thermocouple, Resistance Temperature Detector (RTD), Integrated Circuit (IC) Detectors etc.. They are usually found in Fire alarms, Smartphones, Security devices, Laboratories etc..

• PROXIMITY SENSORS

          A Proximity Sensor is a type of sensor that detects the presence of objects that are placed near to it without any contact. Since there is no contact with the surrounding they have less mechanical parts and have long lasting life and high reliability. Proximity sensors can be implemented using different techniques like Ultrasonic, Infrared or Laser, Photoelectric, Capacitive etc...  An Ultrasonic Proximity Sensor detects an object by emitting Ultrasonic waves and then receives the Ultrasonic signal from the concerned object. It can detect the position, presence and movement of objects. It is mostly used in detection of ground water as it relies on sound waves. Similarly a Photoelectric sensor detects objects by using a light transmitter which emits light waves often Infrared, and a receiver which receives the signals back from the nearby objects. Proximity Sensors are usually used in Mobile Phones, Cars (Parking Sensors), Industries, Aircrafts etc..

• TOUCH SENSORS

          Touch Sensors are a type of sensors which are sensitive to touch, force or pressure. They are one of the most simplest type of sensors which require only a touch to operate. It is as simple as compared to a switch, when there is a contact at the surface of the touch sensor, the circuit closes inside the sensor and flow of current takes place. When the contact is released the circuit is opened and no current flows. There are two common types of touch sensors

          Capacitive Touch Sensors: A capacitive touch sensor works using a single electrode for the flow of current. This electrode is placed behind a glass, wood or plastic frame to stop the flow of current. When a capacitive object like a human body touches the screen or the frame their body increases the capacitance of the electrode and the current flows through it. The measurement circuit will detect the change in capacitance and converts it into a trigger signal. This type of sensor is mostly used in touch screen mobiles and other devices which can be easily handled by a simple touch.

          Resistant Touch Sensor: A resistant touch sensor consists of two layers of films separated by small spacer dots. When you press your finger on the top layer or screen, it touches the bottom screen as it is flexible and the interruption in the electric current is noted by the device, and it calculates the precise location of the point of contact. The device then performs the programmed action. You can activate them with bare fingers, gloves or anything else it does not need to be capacitive as in  the case of capacitive touch sensors, but you can't swipe or use Multi-touch because the electric current can only register one point of contact at a time. They are used in cell phones, refrigerators, washing machines, ovens, and other devices but are slowly getting replaced by capacitive touch sensors.

• UV SENSORS 

          These Sensors measures the intensity of the incident Ultraviolet Radiation. This type of radiation have wavelengths longer than X-Rays. These sensors are used to detect the exposure of ultraviolet radiation to any laboratory or environment or to detect the UV rays incoming from an object. They usually have a transmitter that respond to UV radiation (Input) and send the Electrical signals (Output) to a measuring device for observation or recording the signal. They are mostly used by specialists as it requires some professional skills to handle and only used in specialized works.

• IR SENSORS

          These Sensors emits or detects Infrared Radiation to sense the environment. It is also capable of measuring the heat emitted by any object and also detecting motion of any object. The Infrared Sensor detects the type of radiation which is not visible to human eye. They usually consists of one IR LED which acts as transmitter to send the Infrared waves to the object and another IR diode of same type which acts as a receiver to detect the reflected waves from the object. Sometimes they only have an IR diode which detects the incoming IR waves, this is generally used in an environment prone to Infrared Radiation and only its detection is required. The detector then sends the IR wave signal converted to electrical signal to a device for measuring the frequency of incoming signal or comparing it with the outgoing signal and providing required information. These are mostly used in Astronomy and Laboratories to detect Infrared waves. Other applications include Climatology, Gas detectors, Petroleum Exploration, Water Analysis etc..

ERRORS IN SENSORS
          Sensors are believed to be highly accurate but sometimes there might be errors occurring which can limit a Sensor's Accuracy. Error can be of any type, the measured values can be different from the specified values due to an error in the mechanical part by rough usage or any sort of interference which can affect a sensor's accuracy. Sometimes while dealing with moving objects if the object in observation moves away from the range of a sensor it can cause an error while displaying the result or displays a wrong value. This only happens when the sensor has to deal with moving objects like an Accelerometer or a speedometer. Errors can also be caused with rapid changes in property of object or the measuring property due to any inconvenience in the surroundings or climatic changes. Even sensors can also get affected by the surroundings like interference of sounds, magnetic field etc.. Although these errors are negligible until these effecting Factors are not on a large scale.

SENSORS IN NATURE
          Nature also contains biological sensors similar to those devices described above. Living organisms specially humans have specialized cells that are sensitive to many of the natural parameters like temperature, light, motion, humidity, sound, vibration, electrical fields etc.. Our sensors detect and respond to these parameters but quite different from these mechanical devices. In emergencies we can sometimes detect the type of emergency without even seeing it and our brain makes decisions and helps us to come out of those situations instead of observing and calculating results. In biomedicine sensors which can detect analytes are called Biosensors, such as Cells, Tissues etc. Also plants have sensors to detect environment and respond to it like a touch me not plant which closes its leaves whenever you touch it, an insect eater plant which eats insects when they come in contact with it and many other examples.

          Sensors are one of the emerging and trending technologies in the modern world. It is getting advanced and has a strong hold in the market. Researches and studies are still going on to improve more and more. They are becoming a part in everyday life and its applications are increasing day by day. They are also benefiting from other technologies like Nanotechnology and Artificial Intelligence. Well as I always say there's much more to come and the technology of Sensors will be much more advanced in the coming years


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