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INSTRUMENTATION AND

MEASUREMENTLecture No 01

_________________________________________________________________________________________________________

Zubair Mehmood, Lecturer

Department of Electrical Engineering, University of Gujrat, Gujrat Email: zubair.mehmood@uog.edu.pk

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Recommended Books

Text:

Elements of Electronic Instrumentation and

Measurement. Joseph J. Carr3rd Edition

Reference:

Instrumentation and Measurement

BERLIN . GETZ

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Objectives Be able to list the basic categories of measurement.

Know the meaning of the terms

Accuracy

Precision

Resolution

Reliability Validity

as applied to measurements.

Understand and evaluate the role and nature ofmeasurement error.

Know how to minimize error in measurement.

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Categories of Measurement

Direct Measurement

Indirect Measurement

Null Measurement

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Direct Measurement

Holding the measurand up to some calibrated

standard and comparing the two.

Example

Meter-Stick Ruler

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Indirect Measurement

Indirect Measurement are made by

measuring some thing other than the actual

measurand.

Examples Temperature Measurement

Blood Pressure Measurement

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Null Measurement

Null Measurement are made by comparing a

calibrated source to an unknown measurand

and then adjusting either one or the other

until the difference between them is zero.

Example

Electrical Potentiometer

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Factors in Making

Measurement

Error

Validity

Reliability and Repeatability

Accuracy and Precision Resolution

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Error

Normal Random variations

Neither Mistake nor Blunder

Repeated Measurement Different Instruments

Instrument Operators

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Validity

How well an instrument actually measures

what it purports to measure

Example

Electronic Pressure Sensor Specific Conditions, Specific Range

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Reliability and Repeatability

Reliability: Consistency when the values of

the measurand are discerned to different

trials

Repeatability:Ability of the instrument torepeat the same value when repeatedly

exposed to the same external stimulus

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Accuracy and Precision

Accuracy: Freedom from error

Precision: Exactness of successive

measurements

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Resolution

The Degree to which a measurand can be

broken into identifiable adjacent parts

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Categories of Errors

Theoretical Errors

Static Errors

Dynamic Errors

Instrument Insertion Errors

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Theoretical Errors

Theoretical Models are valid only for specific

range of phenomenon

Example:

Mean Arterial Pressure (MAP)

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Static Errors

Always present even in an unchanging system

These errors are not function of time and frequencyvariations

Reading Errors

Parallax Reading Error

Interpolation Error

Last digit bobble error

Environmental Static Errors Characteristic Static Errors

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Dynamic Errors

When measurand is changing or in motion

during the measurement process.

Inertia of mechanical indicating devices

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Instrument Insertion Errors

Measurement process should not significantly

alter the phenomena being measured

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Weighting a Cow

Home Work