Introduction to Measurement Systems & Devices
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Transcript of Introduction to Measurement Systems & Devices
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INTRODUCTION TOMEASUREMENT SYSTEMS & DEVICES
Module-3
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MODULE OBJECTIVES Upon successful completion of this module, students should
be able to:
Define a measurement system and identify its main elements Explain the role of sensors/transducers in a measurement
system Define the terms sensitivity and linearity of a
sensor/transducer Identify different sensors used in temperature measurements Determine the sensor characteristics through experiments Understand and perform calibration of temperature sensor/transducer.
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INTRODUCTION TO MEASUREMENT SYSTEMS
We use the term ‘measurements’ everyday in our lives Noting the time on our watch/clock Recording the temperature Tracing the speed of a car Estimating electricity consumption, and so on
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INSTRUMENTSAn instrument is a device used to
measure a physical variable. A ruler, for example, provides measurement of length
temperature, distance, pressure, force, humidity
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PROCESS A process is a sequence of operations
carried out to achieve a desired result.
For example, fixing a flat tire is a process. Similarly, maintaining the temperature of a
room within the desired limit is a process.
Manual
Automatic
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MEASUREMENT SYSTEM ELEMENTS Any Measurement system consists of
three basic parts: transducer/sensor signal processor and recorder
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COMPLETE THE CLASSWORK ON QUIA www.quia.com
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SENSOR A sensor is a device that senses a
physical variable, such as temperature, force, or pressure etc
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TRANSDUCER A transducer is a device that converts a
physical quantity into a measurable quantity, usually an electrical signal
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MEASUREMENT SYSTEM EXAMPLE Temperature measurement system
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DEFINITION Transducer – Thermocouple is the
transducer that converts the input temperature to a small voltage (in millivolt).
Signal processor –The signal processor increases the level of the voltage and converts it to a digital format.
Recorder- LED display displays the temperature in digits.
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TASK-1 : GO TO QUIA & ANSWER THE QUESTION
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LINEARITY Some transducers output a signal that is
proportional to the input physicalquantity. These transducers are called linear devices.
Other transducers that don’t have a proportional relationship between the output signal and the input are non-linear devices.
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SENSITIVITY Sensitivity is the ratio of change in the
output signal to the change in the amount of the physical parameter being measured.
Sensitivity = Change in Output / Change in Input
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CALIBRATION Calibration is the comparison of
measurement with a standard
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CALIBRATION Calibration is done by: Measuring the transducer output for
known physical quantities Determining the best mathematical
relation between the input and the output
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TEMPERATURE MEASUREMENT Temperature is the degree of hotness or
coldness measured on a definite scale. The various units for measuring
temperature are celsius, kelvin and fahrenheit.
The SI unit of temperature measurement is the ‘kelvin’.
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TEMPERATURE MEASUREMENT Temperature can be measured using
any one of the following methods depending on the application: Immersion in a gas or liquid Surface Contact with the solid No contact
Measuring device: thermometer, thermistor and thermocouple
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THERMOMETER Mercury thermometer is a temperature
sensor that converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube.
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THERMOCOUPLE Thermocouple is a temperature
transducer that consists of two different metals, joined together at one end
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THERMISTOR The thermistor is a thermally sensitive
resistor, the resistance of which varies with temperature.
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TASK-2 Identify the input physical quantity and the output for the
sensors given in the table.
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LAB ACTIVITY 1