Introduction to Measurement Systems & Devices
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Transcript of Introduction to Measurement Systems & Devices
INTRODUCTION TOMEASUREMENT SYSTEMS & DEVICES
Module-3
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.
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
INSTRUMENTSAn instrument is a device used to
measure a physical variable. A ruler, for example, provides measurement of length
temperature, distance, pressure, force, humidity
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
MEASUREMENT SYSTEM ELEMENTS Any Measurement system consists of
three basic parts: transducer/sensor signal processor and recorder
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SENSOR A sensor is a device that senses a
physical variable, such as temperature, force, or pressure etc
TRANSDUCER A transducer is a device that converts a
physical quantity into a measurable quantity, usually an electrical signal
MEASUREMENT SYSTEM EXAMPLE Temperature measurement system
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.
TASK-1 : GO TO QUIA & ANSWER THE QUESTION
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.
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
CALIBRATION Calibration is the comparison of
measurement with a standard
CALIBRATION Calibration is done by: Measuring the transducer output for
known physical quantities Determining the best mathematical
relation between the input and the output
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’.
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
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.
THERMOCOUPLE Thermocouple is a temperature
transducer that consists of two different metals, joined together at one end
THERMISTOR The thermistor is a thermally sensitive
resistor, the resistance of which varies with temperature.
TASK-2 Identify the input physical quantity and the output for the
sensors given in the table.
LAB ACTIVITY 1