CHHATRAPATI SHIVAJI INSTITUTE OF TECHNOLOGY MECHATRONICS STUDY OF SENSOR 2014-2015 PROJECT GUIDE: Mr. pradeep agrawal (Assi.prof.) PROJECT BY: Humendra sahu (Mex 3rd sem)

Introduction Transducer Sensor (e.g., thermometer) a device that converts a primary form of energy into a corresponding signal with a different energy form Primary Energy Forms: mechanical, thermal, electromagnetic, optical, chemical, etc. take form of a sensor or an actuator Sensor (e.g., thermometer) a device that detects/measures a signal or stimulus acquires information from the “real world” Actuator (e.g., heater) a device that generates a signal or stimulus sensor intelligent feedback system real world actuator

Categorization of Sensor Classification based on physical phenomena Mechanical: strain gage, displacement (LVDT), velocity (laser vibrometer), accelerometer, tilt meter, viscometer, pressure, etc. Thermal: thermal couple Optical: camera, infrared sensor Others … Classification based on measuring mechanism Resistance sensing, capacitance sensing, inductance sensing, piezoelectricity, etc. Materials capable of converting of one form of energy to another are at the heart of many sensors. Invention of new materials, e.g., “smart” materials, would permit the design of new types of sensors.

Paradigm of Sensing System Design

Instrumentation Considerations Sensor technology; Sensor data collection topologies; Data communication; Power supply; Data synchronization; Environmental parameters and influence; Remote data analysis.

Sensor System Measurement Measurement output: Physical phenomenon Sensor System Measurement Output Measurement output: interaction between a sensor and the environment surrounding the sensor compound response of multiple inputs Measurement errors: System errors: imperfect design of the measurement setup and the approximation, can be corrected by calibration Random errors: variations due to uncontrolled variables. Can be reduced by averaging.

Sensors Definition:A sensor is a device that detects events or changes in quantities and provides a corresponding output, generally as an electrical or optical signal; for example, a thermocouple converts temperature to an output voltage. Classification of Sensors Mechanical quantities: displacement, Strain, rotation velocity, acceleration, pressure, force/torque, twisting, weight, flow Thermal quantities: temperature, heat. Electromagnetic/optical quantities: voltage, current, frequency phase; visual/images, light; magnetism. Chemical quantities: moisture, pH value

Specifications of Sensor Accuracy: error between the result of a measurement and the true value being measured. Resolution: the smallest increment of measure that a device can make. Sensitivity: the ratio between the change in the output signal to a small change in input physical signal. Slope of the input-output fit line. Repeatability/Precision: the ability of the sensor to output the same value for the same input over a number of trials

Accuracy vs. Resolution True value measurement

Accuracy vs. Precision Precision without accuracy Accuracy without precision Precision and accuracy

Specifications of Sensor Dynamic Range: the ratio of maximum recordable input amplitude to minimum input amplitude, i.e. D.R. = 20 log (Max. Input Ampl./Min. Input Ampl.) dB Linearity: the deviation of the output from a best-fit straight line for a given range of the sensor Transfer Function (Frequency Response): The relationship between physical input signal and electrical output signal, which may constitute a complete description of the sensor characteristics. Bandwidth: the frequency range between the lower and upper cutoff frequencies, within which the sensor transfer function is constant gain or linear. Noise: random fluctuation in the value of input that causes random fluctuation in the output value

Attributes of Sensors Operating Principle: Embedded technologies that make sensors function, such as electro-optics, electromagnetic, piezoelectricity, active and passive ultraviolet. Dimension of Variables: The number of dimensions of physical variables. Size: The physical volume of sensors. Data Format: The measuring feature of data in time; continuous or discrete/analog or digital. Intelligence: Capabilities of on-board data processing and decision-making. Active versus Passive Sensors: Capability of generating vs. just receiving signals. Physical Contact: The way sensors observe the disturbance in environment. Environmental durability: will the sensor robust enough for its operation conditions

Typically interested in electronic sensor General Electronic Sensor Sensor Systems Typically interested in electronic sensor convert desired parameter into electrically measurable signal General Electronic Sensor primary transducer: changes “real world” parameter into electrical signal secondary transducer: converts electrical signal into analog or digital values analog signal real world primary transducer secondary transducer Usable value sensor Typical Electronic Sensor System microcontroller signal processing communication input signal (measurand) network display sensor sensor data analog/digital

Types of sensor contact type: e.g. thermometer. Non-contact type:  These types of sensor are required to be in physical contact with the object being sensed and use conduction to monitor changes in physical state They can be used to detect solids, liquids or gases over a wide range of physical change e.g. thermometer. Non-contact type: These types of temperature sensor use convection and radiation to monitor changes like in temperature. They can be used to detect liquids and gases that emit radiant energy as heat rises and cold settles to the bottom in convection currents or detect the radiant energy being transmitted from an object in the form of infra-red radiation (the sun). e.g. ir sensor.

Cotact type Analogue Sensors Analogue Sensors produce a continuous output signal or voltage which is generally proportional to the quantity being measured. Physical quantities such as Temperature, Speed, Pressure, Displacement, Strain etc are all analogue quantities as they tend to be continuous in nature. For example, the temperature of a liquid can be measured using a thermometer or thermocouple which continuously responds to temperature changes as the liquid is heated up or cooled down Digital Sensors As its name implies, Digital Sensors produce a discrete digital output signals or voltages that are a digital representation of the quantity being measured. Digital sensors produce a Binary output signal in the form of a logic “1” or a logic “0”, (“ON” or “OFF”). This means then that a digital signal only produces discrete (non-continuous) values which may be outputted as a single “bit”, (serial transmission) or by combining the bits to produce a single “byte” output (parallel transmission).

Non –contact type: Ir sensor(infrared)  IR Sensors work by using a specific light sensor to detect a select light wavelength in the Infra-Red (IR) spectrum. By using an LED which produces light at the same wavelength as what the sensor is looking for, you can look at the intensity of the received light. When an object is close to the sensor, the light from the LED bounces off the object and into the light sensor. This results in a large jump in the intensity, which we already know can be detected using a threshold Detecting Brightness Since the sensor works by looking for reflected light, it is possible to have a sensor that can return the value of the reflected light. This type of sensor can then be used to measure how "bright" the object is. This is useful for tasks like line tracking

Applications Automobile industry Defence system weapens Sonar system in sub-marrines Ultrasonic to measure distance Preassure sensor in touch screen

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