part 12-elec buk(final)

8/11/2019 PART 12-Elec Buk(Final)

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PART12ELECTRONIC INSTRUMENTATIONS

INSTRUMENTATION Measurement of quantities

Refers to instruments ranging from basic test instruments to complex scientific

instruments

I. INSTRUMENTS and MEASUREMENTS

1. Instruments

Devices that can give quantitative description on a given parameters Provides a visual indication of the quantity being measured, the instruments

sometimes furnishes a permanent record Basic Functions:

a. indicatingb. recordingc. controlling for industrial process situationsd. monitoring remote signals

. E!ectrica! Units

as with any quantitative science, a system of units is required before one can

make a quantitative evaluation of parameters measured Fundamenta! "uantitiesa. ength !meter"b. Mass! kilogram"c. #ime !second"d. uminous intensity !candela"e. #emperature !degree $elvin"f. %lectric current !ampere"

#. Measurement Standards

&nstrument or device having a recogni'ed permanent value that is used a s a

reference or criterion

a. Internationa! Standards Defined by international agreement

Macro Inte$rated Trainin$ and Re%ie& Center E!'c(r)ni*

Dry(ell


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Electronic Instrumentations 1- #

/00 4 /6 33 6

Precision indication of the closeness with which a repeated set of measurements of the

same variable agrees with the average of the set of measurements.Mathematically expressed as8

Precision 3 1+ :*

**;

n

nn

+here2 9n the value of the nth measurement 9n the average of the set of the n measurements


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1+0 Electronic Instrumentations

II. METER MO>EMENTS

Basic Meter Mo%ements in Ana!o$ T-e Meters

*asic meter movements used in direct current measurements can be traced to

s discovery of the relation between current and magnetism

1. ?@ Arson%a! Meter

Permanent Magnet Moving (oil !PMM(" meter movement

-ses a ?taut band@ suspension system which provides a more sensitive meter

movement (onsist of a moving coil, a spring and permanent magnet

D( use but can also be use in ;( application only if it has rectifiers

Most widely used meter movement for measuring direct current or voltage and

resistance

. E!ectrod-namometer

(onsists of a moving coil called ?armature@ that is free to move within a

magnetic field set up by two stationary field coils

E!'c(r)ni* Macro Inte$rated Trainin$ and Re%ie& Center


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Electronic Instrumentations 1- o!tmeter

Measures D( voltage across the element or circuit being measured

a. Concet o2 Idea! >o!tmeter Resistance of the ideal voltmeter is infinite

,. ?C >o!tmeter Mu!ti!ier *asic D>;rsonval meter movement can be converted to a D( voltmeter byconnecting a mu!ti!ier Rsin series with the meter movement. #he purpose of the multiplier is to extend the voltage range of the meter

Mu!ti!-in$ 2actor o2 %o!tmeter 3Rm

Rs1

>

>

m

L

ere2 17 max. voltage that voltmeter can measure 1m7 voltage drop across the meter Rm7 internal resistance of the meter Rs7 multiplier5series resistance

c. Sensiti%it-DS o2 te meter mo%ement;id in determining the value of the multiplier

Reciprocal of the full scale deflection current!&B)"

S3FSI

1



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1+ Electronic Instrumentations

Re%ie& "uestion (alculate the value of the multiplier resistance non the A071 range of a D(

voltmeter that uses a A007u; movement with an internal resistance of C $. So!ution:

(alculate the sensitivity of the meter 2 Su;A00

/ C $51

(ompute Rs using2 Rs !) x range" 7 Rm !C $51 x A0 1" 7 C $

3E $

d. >o!tmeter Loadin$ E22ects #he voltage across a component is less whenever the voltmeter is connected

and this is the !oadin$ e22ect #his condition will result into an error called !oadin$ error

#. Te Ommeter

&nstrument designed around a basic meter movement that is capable of

measuring resistance (onstructed with a basic D>;rsonval meter movement in con:unction with a

battery and a resistor

0. Te Mu!timeter

(ombined three circuits in a single instrument

1olt7ohm7milliammeter !1=M" is a general purpose test instrument that has the

necessary circuitry to measure ac or dc voltage, direct current or resistance #ypical commercial 1=M is normally designed around a basic A0u; meter

movement Bundamental applications is to measure voltage, current and resistances



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Electronic Instrumentations 1-

-sing the ohmmeter 5ohmmeter function of 1=M, one can have a continuity

check or even check semiconductor diodes

III. AC METERS

1. AC >o!tmeter G Ha!2 a%e D( operated D> ;rsonval meter movement can also be used to measure ;(

voltage by process of half wave rectification

Rs 3 RmI

>

?C

?C 3 Rm

I

>0o!tmeter G Fu!! a%e

Bull wave rectification can also be used to measure ;( voltage from a D(

operated D> ;rsonval meter movement set7up

Rs RmI

>

?C

?C Rm

I

>F.6

?C

rms



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Sac 3 6. S?Cere:Rs 4 multiplier resistor&D( 4 full scale meter current, &B)

)ac ;( )ensitivity)D( D( )ensitivity

I>. BRI?=ES

;re instruments for making comparison measurement, they are used to

measure resistance, inductance. (apacitance and impedance. =perates in null indication principle meaning indication is independent of the

calibration

1. ?C Brid$es

a. Te eatstone Brid$e Devised by ).< (hristie in /EFF

; D( type bridge which accurately measure resistances

(onsist of two parallel resistance branches with each branch containing two

series elements usually resistors; D( voltage source provides the source of current to the resistance network

; null detector usually a galvanometer is connected between the parallel

branches to detect a condition of balance

R4 31R

#RR

ote, for a balanced bridge the galvanometer reading is 'ero

+hen the bridge is unbalanced, the pointer in the galvanometer deflects thus

exhibit sensitivity. Sensiti%it- of the galvanometer is the deflection per unitcurrent

,. e!%in Brid$e Modified version of the +heatstone *ridge



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Electronic Instrumentations 1- 11

#he purpose of the modification is to eliminate the effects of contact and lead

resistances when measuring very low resistances Displays high degree of accuracy in measuring resistance of range / to /G

-ses a second set of arms and is referred to as the $elvin Double *ridge

Rlc represents the lead and contact resistances present in the +heatstone

*ridge

c. A!ications +heatstone bridge used to measure D( resistances of various types of wires

+heatstone *ridge is used in locating faults in the cable

Murra- Loo Testis the simplest of loop test and is used principally to locateground faults in sheathed cables

>ar!e- Loo Test is a modification of Murray loop test which is a special+heatstone bridge configuration used to locate shorts between conductors orfaults to ground in conductors

. AC Brid$es *asically a +heatstone *ridge, with arms that are impedances instead of

purely resistance -sed to measure capacitance, inductance and impedance

a. Simi!ar+ An$!e Brid$e Measure the impedance of a capacitive circuit

)ometimes called the capacitance comparison bridgeor the series resistancecapacitance bridgeRefer to the preceding figure2



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R4

1R

#RR C4 3

R

#C1R

,. Oosite An$!e Brid$e Measures the impedance of an inductive circuit

$nown as the


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Electronic Instrumentations 1- 1#

R4 31R

#RR

L4 3RR#C

d. ien Brid$e &t can measure the equivalent series components or the equivalent parallel

components of an impedance -sed extensively as a feedback arrangement for a circuit called the +ien

*ridge oscillator

e. Radio FreJuenc- Brid$e -sed in laboratories to measure the impedance of both capacitance and

inductive circuits at higher frequencies Measurement technique used in this bridge is known as the substitution

technique



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R4 51C1C7C

#R K

*4 50C

1

0C

1

7

1

K

ote2 (/> and (H> are rebalance values

2. Scerin$ Brid$e -sed to measure capacitance

=ften used to Measure insulating properties such as for phase angles very

nearly 30 degrees #he standard arm contains only a capacitor which is usually a high quality mica

capacitor



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Electronic Instrumentations 1- 1. ELECTRONIC INSTRUMENTS

1. Common and E!ectronic Measurin$ Instruments

a. >o!t+Om+Mi!!iammeter 7>OM5 Rugged, accurate instrument but lacks of sensitivity and high input resistance

,. E!ectronic >o!tmeter1oltmeters that use active devices such as vacuum tubes, transistors or op7

amps &t has the advantage of having very high input resistance

;nalog %1M 4 uses deflection type displayDigital %1M 4 uses numerical type display

c. Transistor >o!tmeter -ses transistor as its active device

d. >ector >o!tmeter Measure voltages with both magnitude and phase

e. >ector Imedance Meter Measures impedances with both magnitude and phase

2. Osci!!oscoe



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%lectronic display device that contains cathode7ray tube !(R#" that produces

visible patterns that are graphical representations of electrical signals =scilloscope consist of the following ma:or subsystems2

/. (athode Ray7#ubeC. 1ertical amplifierF.


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c. Radio FreJuenc- =enerators;ssigned to provide output signal over a wide range of frequencies from

approximately F0 $


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Real time analy'er which means that it simultaneously displays the amplitude

of all signals in the frequency range of the analy'er Provides information about the voltage or energy of the signal as a function of

frequency Provides graphical display on a (R#

d. Fourier Ana!-er *ased from the calculation of the discrete Bourier transform using an algorithm

called the fast Bourier #ransform -ses digital signal7processing technique to provide measurements that go

beyond the capabilities of spectrum analy'er Primarily digital instruments, interfacing to a computer or other digital systems

is relatively straightforward Provides a high degree of accuracy, stability and repeatability in spectrum

TEST OURSELF 12Re%ie& "uestions/. %rrors in analog meter reading due to your physical position with respect to the meter scale

a. parallax error

b. angular errorc. linear errord. deviation

Ans&era. parallax error

C. &nstrument having recogni'ed permanent or stable value that is used as a reference.a. standard instrumentb. reference instrumentc. fixed instrumentd. ideal instrument

Ans&er a. standard instrument

F. #he smallest change in measured variable to which an instrument will respond.a. quanti'ed valueb. resolutionc. minimumd. step si'e



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Ans&erb. resolution

H. +hat is the most common type of meter movementKa. Bixed coilb. &ron 1anec. D> ;rsonvald. %lectrodynamometer

Ans&er c. D> ;rsonval

A. +hat ammeter is mostly used in measuring high frequency currentsKa. electrostaticb. moving7coilc. dynamometerd. thermocouple

Ans&erd. thermocouple

I. &t is a device tat mechanically measure the output power of a motora. Meggerb. (oncentric7vane instrumentc. radial7vane instrumentd. dynamometer

Ans&er d. dynamometer

L. %rror in voltmeter reading is due toa. loadingb. battery agingc. conversiond. insertion

Ans&er a. loading

E. &t is a meter that requires its own power source.a. voltmeterb. ammmeterc. wattmeterd. ohmmeter

Ans&erd. ohmmeter

3. %rror in ohmmeter reading is due to2a. insertionb. loadingc. battery agingd. meter friction

Ans&erc. battery aging

/0. #he 'ero ad:ust control in an analog type ohmmeter is used to



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a. compensate for the differing internal battery voltageb. make sure the pointer is moving correctly

c. align the infinity resistance positiond. align the 'ero7voltage position

Ans&er a. compensate for the differing internal battery voltage

//. +ith no added gadget, D>;rsonval meter can be used to measurea. ;(b. ;( and D(c. D(d. dynamic resistance

Ans&er c. D(

/C. #ype of power line frequency meters composed of vibrating ion reeds placed in alternatingmagnetic field

a. induction typeb. electrodynamic typec. resonant typed. vibrating reed type

Ans&er d. vibrating reed type

/F. %lectrodynamometer can be used to measurea. ;(b. D(c. ;( and D(d. dynamic resistance

Ans&erc. ;( and D(

/H. ;n iron vane is used to measurea. ;(b. ;( and D(c. D(d. dynamic resistance

Ans&er c. ;( and D(

/A. &t is the reciprocal of the full scale current of a meter.a. transconductanceb selectivityc. sensitivity

d. dynamic resistance

Ans&er c. sensitivity

/I. +hat is the device that is used to measure current without opening the circuitK



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a. multi7meter

b. megger testerc. ammeterd. clamp probe

Ans&erd. clamp probe

/L. ; bridge used to locate accidental ground on communication and power lines.a. =wen>s bridgeb. Murray loopc. )chering bridged. $elvin bridge

Ans&er b. Murray loop

/E. ;n ;( bridge that measures capacitance and dissipation factor

a. =wen>s bridgeb. )chering bridgec.


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1+ Electronic Instrumentations

CC. ; is a device that can test all pins of an &( at the same time.a. logic probe

b. pulserc. current tracerd. logic clip

Ans&erd. logic clip

CF.


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Electronic Instrumentations 1- #

CE. +hat is the distortion that is caused by non7linear operation of amplifierKa. harmonic distortionb. frequency distortionc. time distortiond. no distortion

Ans&er a. harmonic distortion

C3. #his device extend the range of a potentiometer very easily and convenientlya. volt canb. volt boxc. volt containerd. volt drawer

Ans&er b. volt box

F0. &t is the null detector of +heatstone bridge that indicates balance.a. goniometerb. oscilloscopec. galvanometerd. electrodynamometer

Ans&erc. galvanometer

F/. &t is a precision instrument that operates on the null principle with primary application ofmeasuring unknown voltages.

a. potentiometerb. rheostatc. bridgesd. 1=M

Ans&er a. potentiometer

FC. &t is a precision voltage divider network, sometimes called a resistance ladder used incon:unction with a potentiometer.

a. ladder circuitsb. hybrid circuitsc. volt boxd. black box

Ans&er c. volt box

FF. +hat do you call the condition of a bridge that indicates 'ero current flowing through thedetectorK

a. unbalanceb. balancec. ideald. perfect

Ans&erb. balance



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FH. ; term used to indicate that no current is flowing through a galvanometer, hence the pointer is

resting at center scale 'ero meaning the bridge is balanceda. o indicationb. Nero indicationc. *lank indicationd. ull indication

Ans&erd. ull indication

FA. #his is a device that is made out of similar metals wherein contact potential is developedacross the :unction of two metals.

a. thermocoupleb. photocellc. 'ero setd. thermometer

Ans&era. thermocouple

FI. &t is the circuit in oscillator that provides amplification of the signal to be applied to the verticaldeflection plate

a.


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Electronic Instrumentations 1-

part 12-elec buk(final)

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