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Sensors: Different Types of SensorsTABLE OF CONTENTS:
1. Sensors: Different Types of Sensors2. Type1: Temperature3. Type2: IR Sensors4. Type3: UV Sensors5. Type4: Touch Sensor6. Type5: Proximity Sensor7. Advanced Sensor Technology
Sensors are sophisticated devices that are frequently used to detect and respond to electrical or optical signals. A Sensor converts the physical parameter (for example: temperature, blood pressure, humidity, speed, etc.) into a signal which can be measured electrically. Let’s explain the example of temperature. The mercury in the glass thermometer expands and contracts the liquid to convert the measured temperature which can be read by a viewer on the calibrated glass tube.
Criteria to choose a SensorThere are certain features which have to be considered when we choose a sensor. They are as given
below:
1. Accuracy
2. Environmental condition - usually has limits for temperature/ humidity
3. Range - Measurement limit of sensor
4. Calibration - Essential for most of the measuring devices as the readings changes with time
5. Resolution - Smallest increment detected by the sensor
6. Cost
7. Repeatability - The reading that varies is repeatedly measured under the same environment
Classification of SensorsThe sensors are classified into the following criteria:
1. Primary Input quantity (Measurand)
2. Transduction principles (Using physical and chemical effects)
3. Material and Technology
4. Property
5. Application
Transduction principle is the fundamental criteria which are followed for an efficient approach. Usually,
material and technology criteria are chosen by the development engineering group.
Classification based on property is as given below:
· Temperature - Thermistors, thermocouples, RTD’s, IC and many more.
· Pressure - Fibre optic, vacuum, elastic liquid based manometers, LVDT, electronic.
· Flow - Electromagnetic, differential pressure, positional displacement, thermal mass, etc.
· Level Sensors - Differential pressure, ultrasonic radio frequency, radar, thermal displacement, etc.
· Proximity and displacement - LVDT, photoelectric, capacitive, magnetic, ultrasonic.
· Biosensors - Resonant mirror, electrochemical, surface Plasmon resonance, Light addressable
potentio-metric.
· Image - Charge coupled devices, CMOS
· Gas and chemical - Semiconductor, Infrared, Conductance, Electrochemical.
· Acceleration - Gyroscopes, Accelerometers .
· Others - Moisture, humidity sensor, Speed sensor, mass, Tilt sensor, force, viscosity.
Surface Plasmon resonance and Light addressable potentio-metric from the Bio-sensors group are the
new optical technology based sensors. CMOS Image sensors have low resolution as compared to charge
coupled devices. CMOS has the advantages of small size, cheap, less power consumption and hence are
better substitutes for Charge coupled devices. Accelerometers are independently grouped because of
their vital role in future applications like aircraft, automobiles, etc and in fields of videogames, toys,
etc. Magnetometers are those sensors which measure magnetic flux intensity B (in units of Tesla or
As/m2).
Classification based on Application is as given below:
· Industrial process control, measurement and automation
· Non-industrial use – Aircraft, Medical products, Automobiles, Consumer electronics, other type of
sensors.
Sensors can be classified based on power or energy supply requirement of the sensors:
· Active Sensor - Sensors that require power supply are called as Active Sensors. Example: LiDAR
(Light detection and ranging), photoconductive cell.
· Passive Sensor - Sensors that do not require power supply are called as Passive Sensors. Example:
Radiometers, film photography.
In the current and future applications, sensors can be classified into groups as follows:
· Accelerometers - These are based on the Micro Electro Mechanical sensor technology. They are
used for patient monitoring which includes pace makers and vehicle dynamic systems.
· Biosensors - These are based on the electrochemical technology. They are used for food testing,
medical care device, water testing, and biological warfare agent detection.
· Image Sensors - These are based on the CMOS technology. They are used in consumer
electronics, biometrics, traffic and security surveillance and PC imaging.
· Motion Detectors - These are based on the Infra Red, Ultrasonic, and Microwave / radar technology.
They are used in videogames and simulations, light activation and security detection.
Level SensorsTABLE OF CONTENTS:
1. Level Sensors2. Classification3. Resistive, Capacitive4. Pressure, Hall Effect, Ultrasonic5. Radar Level, Optical6. Selection of Sensors
On 28th March 1979, at Three Mile Island nuclear power plant in USA, part of the core melted in the # 2 reactor. The TMI-2 reactor was destroyed. The cause of the accident was the little malfunction in the secondary cooling circuit which allowed temperature in the primary coolant to rise. This caused the reactor to shut down automatically. This situation developed because the level controls turned off the coolant to the reactor when they detected presence of cooling water near the top of the tank. The water at the top was not because of the tank got completely filled, it was because the water was too little in the tank that it got boiled and swelled up to the top of the tank.
The incident is an example signifying the importance of fluid level sensors and their proper functioning.
They are important not only in nuclear plants but in lot many applications. Every car, truck and motorcycle
is equipped with a fuel level sensor to measure the amount of gasoline left in the fuel tank. In addition,
there are sensors for level measurement of engine oil, brake / power steering fluid, cooling water,
windshield cleaning liquid, etc. Industrial applications include liquid level sensing in water treatment tanks,
transport and storage tanks, in the petrochemical industry for liquids such as petrol, etc. Liquid level
measurement is important in household applications for devices such as automated coffee machines,
water dispensers, juice squeezers, water evaporators, steamers, fridges and freezers, boilers, heating
systems, dishwashers, washing machines, steam irons, etc.
In short, level sensors are one of the very important sensors and play very important role in variety of
consumer/ industrial applications. As with other type of sensors, level sensors are available or can be
designed using variety of sensing principles. Selection of an appropriate type of sensor suiting to the
application requirement is very important.
WHAT IS A LEVEL SENSORWide spectrum of sensors is available in the market and commonly, they are classified based on the
specific application of the sensor. Sensor used for measuring humidity is termed as humidity sensor, the
one used for measurement of pressure is called pressure sensor, sensor used for measurement of
displacement is called position sensor and so on though all of them may be using the similar sensing
principle. In a similar fashion, the sensor used formeasurement of fluid levels is called a level sensor.
Quite obvious from its name, level sensors are used to measure the level of the free-flowing substances.
Such substances include liquids like water, oil, slurries, etc as well as solids in granular/powder form
(solids which can flow). These substances tend to get settled in the container tanks due to gravity and
maintain their level in rest state. Level sensors measure their level against a pre-set reference.
How to Save a Sensor Value in the EEPROM of the ArduinoARD018
Summary Description Circuit Diagram Video Code Components
The EEPROM stands for Electrically Erasable Programmable Read Only Memory. In an EEPROM the
data can be written with the help of electrically programming the chip. EEPROM memory is widely used in
microcontroller systems where some particular data need to be retained each time the system is turned
on and to save particular data before the system is powered off.The EEPROM memory chips can be
interfaced in a microcontroller chip usually with the help of serial communication protocols. In case of
small applications where only a few bytes needs to be stored the extra EEPROM chips are not preferred
since it add extra complexity in the hardware, coding and increase the cost of the system. Hence most of
the microcontrollers are provided with small sized built-in EEPROM chip which can be used to store data
in small applications.
The Arduino board has an AVR microcontroller in it which also has a built-in EEPROM memory. The
memory size varies with the Arduino boards and the microcontroller used in them. A microcontroller might
need to store its data like sensor value, or a particular count or image data for a long period of time uses
the EEPROM memory. The EEPROM memory is also used to save the data before the system switches
itself off so that the same data can be retained next time when the system is turned on. This particular
project demonstrates how to save the last read value from a senor into the built-in EEPROM of Arduino
before it is powered off, so that the next time it is powered on the same data can be read.
