Pengukuran Besaran Listrik ~Electrical Measurements~ PERTEMUAN KE-3 PERTEMUAN KE 3 C C S CS O CHARACTERISTICS OF MEASURING INSTRUMENT 23/09/2011 MEASURING INSTRUMENT
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Pengukuran Besaran Listrikg~Electrical Measurements~
PERTEMUAN KE-3PERTEMUAN KE 3
C C S CS OCHARACTERISTICS OF MEASURING INSTRUMENT
23/09/2011
MEASURING INSTRUMENT
Type of Measuring Instrumentsyp g
→Passive→Passive→Active1st Category
Instruments are divided according to whether the instrument output is entirely produced by the quantity being measured or whether the quantity q y g q ybeing measured simply modulates the magnitude of some external power source
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of some external power source.
Passive InstrumentThe energy expended gy pin moving the pointer is derived entirely fromis derived entirely from the change in pressure measured: there are nomeasured: there are no other energy inputs to hthe system.
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Active Instrument
The energy in the output signal comesoutput signal comes from the external power source
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Type of Measuring Instrumentsyp g
→Null-type→Null type→Deflection-type2nd Category yp
Th tit b i d iThe quantity being measured is displayed in terms of the amount ofdisplayed in terms of the amount of movement of a pointer.
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Type of Measuring Instrumentsyp g
Null-typeNull type
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Type of Measuring Instruments
Null-type
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Type of Measuring Instrumentsyp g
Deflection-typeDeflection type
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Type of Measuring Instrumentsyp g
→Analog-type→Analog type→Digital-type
3rd Category g yp
•An analogue instrument gives an output that varies continuously as the quantity being measured changes.continuously as the quantity being measured changes.
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Type of Measuring Instrumentsyp g
A l tAnalog-typeTh t t hThe output can have an infinite number of values within the rangethat the instrument isthat the instrument is designed to measure.
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Type of Measuring Instrumentsyp g
Di it l tDigital-typeA di it l i t t hA digital instrument has an output that varies in discrete steps and so can only have a finitecan only have a finite number of values
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Static Characteristics of Measuring Instruments
1. True ValueExact value/perfectly
t lcorrect value
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Static Characteristics of Measuring Instruments
2. Accuracy and inaccuracyThe accuracy of an instrument is a measure of how close theis a measure of how close the output reading of theinstrument is to the correct value
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value
Accuracy and inaccuracy…
Eq:qA voltmeter of range 0–10 volth d i f 1 0% fhas a quoted inaccuracy of ±1.0% f.s.
the maximum error to be expected in any reading is 0.1 V.
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Static Characteristics of M i I t tMeasuring Instruments
3. Precision/repeatability3. Precision/repeatabilityPrecision is a term that describes an instrument’s degree of freedom from random errorsof freedom from random errors.
Large number of readings are taken ofLarge number of readings are taken of the same quantity by a high precision
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instrument,
Precision/repeatability….p y
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Static Characteristics of M i I t tMeasuring Instruments
4. Range4. RangeThe range of an instrumentThe range of an instrument defines the minimum and
i l f imaximum values of a quantity that the instrument is designedthat the instrument is designed to measure.
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Static Characteristics of M i I t tMeasuring Instruments
5. Linearityy
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Static Characteristics of M i I t tMeasuring Instruments
6. Sensitivityy
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