Measurement 1 2

8/9/2019 Measurement 1 2

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ec r ca easuremen s

Code: EPM1202

Lecture: 4 Tutorial: 2 Total: 6

Dr. Ahmed Mohamed Azmy

Department of Electrical Power and Machine Engineering

-

Faculty of

Engineering Tanta University


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Charge

Unit coulomb (C)

One coulomb is equivalent to one ampere second

1 coulomb = 6.24 x 10 electrons

electricity, which flows past a given point in an

electric circuit when a current of one ampere is

= .


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Force

Unit Newton (N)

One Newton is equivalent to kilogram metre per

,

acceleration of one metre per second squared when

app e o a mass o one ogram

, .

Where “m” is the mass in kilo rams and “a” is the

acceleration in metres per second squared


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Work

Unit joule (J)

One joule is equivalent to one Newton metre

The joule is defined as the work done when a

force of one Newton is a lied throu h a

distance of one metre in the direction of force

W = F . s

Where: “W” is the work done on a body in joules, “F” is

the force in Newton and “s” is the distance in metres

moved by the body in the direction of the force


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Power

Unit Watt (W)

One watt is one joule per second

The power is defined as the rate of doing work

P = W / t

Where: “P” is power in watts, “W” is the work

done in oules and “t” is the time in seconds


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Electrical potential

Unit Volt (V)

One volt is equivalent to one joule per coulomb

One volt is the potential difference between two

oints in a conductor carr in a current of one

ampere and dissipates a power of one watt

coulombsampereampereampereV ====

s.


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Resistance and conductance

Unit ohm (Ω)

one ohm is equivalent to one volt per ampere

It is defined as the resistance between two points

of one volt applied at the two points produces a

current flow of one ampere in the conductor

Ω= V

R


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obtaining information about magnitude of a quantity

The magnitude of quantities can be indicated by

scale in the analogue instruments

It is also possible to indicate the value in the formof a decimal number in digital instruments


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Measuring Instrument

Measuring Instrument is a device that makes

possible direct reading of values of a quantity being

measured

, ,

in order to determine values with required

specifications


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The measuring instrument is used to perform one of the following functions:

• Indication

• ecor

• Control


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Instrument functions

Indication Record Control

To measure

and indicate the

To measure The device is

e ui ed with aunknown value

with the suitableunknown value

for further

control system to

regulate a

utilization certa n process


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Measurement ran e

For any measuring device, the measurement range

is the maximum value of the quantity, which can be

measured

True value

obtained without any errors


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Nominal value

It is the standard value of the variable as given by

the manufacturer under standard conditions

Calibration

The calibration procedure is used to test the accuracyof measuring instruments

It is an operation to create the relationship between

quantity values provided by measurement standardsand the corresponding indications of measuring

system, carried out under specified conditions and

including evaluation of measurement uncertainty

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Measurement 1 2