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Types of electrical measuring instruments:

Electric measuring instruments are used to measure out electrical parameters. The common uses of electrical measuring instruments are current, voltage and resistance measurements. Other electrical measuring instruments include capacitance, inductance and frequency measurements.

To get an accurate reading of electric parameters such as voltage, current and resistance, the electrical measuring instruments must be calibrated. In that location are many calibration methods used in electrical measuring instruments which depend on the measurement type. This entails connecting them to a known standard or device with like properties.

Electric current measurements: Voltage across a stock-still resistor is proportional to the current flowing through it. The electric current can exist measured by connecting a resistor in series with the circuit and measuring the voltage across the resistor.

Voltage measurements: The voltage between two points tin can be measured by connecting a voltmeter in parallel with the load.

Resistance measurements: Resistance is measured by applying a known voltage across a resistor and measuring the current flow.

Capacitance measurement: Capacitance is measured past applying a known voltage and measuring the accuse that accumulates on the capacitor plates.

Inductance measurements: Inductance is measured by applying a known electric current and measuring the voltage across the inductor.

Frequency measurements: Frequency is measured by counting the number of times the waveform repeats in a given period.

Indicating instruments are used to display the voltage, current, or power of electricity. The indicating musical instrument is also known as a meter. Types of indicating instruments: indicating instruments may be analogue or digital. Normally used indicating instrument types include voltmeters, ammeters and watt meters. Indicating instruments tin further be classified past their technology such as electromagnetic indicating instruments, magnetic indicating instruments and thermal indicating instruments.

Measurements involve the use of instruments every bit a physical means of information mining quantities or variables.

The history of development of electrical measuring instruments is divided into iii categories.

1)Mechanical measuring instruments

2)Electrical measuring instruments

three)Electronic measuring  instruments

In this article we will discuss only types of electrical measuring instruments. Electrical methods of indicating the output of the detectors are more Rapid than mechanical methods. It is unfortunate that an electrical system normally depends upon a mechanical meter movement as indicating device. This mechanical move has some inertia and therefore these instruments have a limited fourth dimension response.

 Electrical measuring instruments are classified into 2 categories. They are

1) Absolute instruments

ii) Secondary instruments

ane) Absolute instruments ::

These absolute instruments requite the magnitude of the quantity under measurement in terms of concrete constants of the instrument. These accented instruments are standard and are used laboratories. Examples of these instruments are tangent galvanometer Rayleigh'southward current balance.

2) Secondary instruments ::

 These instruments are so constructed that the quantity being measured tin but exist measured past observing the output indicated by the instrument. The instruments are calibrated by comparing with an absolute instruments or another secondary instruments which has already been calibrated against an absolute musical instrument.

Working with absolute instruments for routine work is time consuming since every time a measurement is made , it takes a lot of fourth dimension to compute the magnitude up the quantity under measurement. Therefore secondary instruments are nearly normally used. Absolute instruments are seldom used except in standards institutions while Secondary instruments find usage about in every sphere of measurement. A voltmeter, a glass thermometer and pressure approximate are examples of secondary instruments.

These secondary instruments are classified into 3 types :

i) Indicating instruments

2) Recording instruments

3) Integrating instruments

1) Indicating instruments ::

     These instruments will give instantaneous values of the quantity to be measured. Calibration and pointer machinery are invalid. PMMC,MI, dynamometer wattmeter, frequency meter, power gene meter are examples.

2) Recording instruments ::

       These instruments records the value to exist measured or observed. Recorded over a graph paper by a lite weight pen.These are used to notice load variation continuously. Examples are recording voltmeter, recording wattmeter, storage oscilloscope.

3) Integrating instruments ::

       These instruments add the measured value to the existing value. These instruments volition give the total electricity consumed over a catamenia of time. Energy meter or KWhr meter ,kVARh meter and ampere hour meter.

                   Depending on the way electrical instruments nowadays result of measurements they tin can be classified into 2 major categories.

1) Deflection type instruments

ii) Nil blazon instruments

1) Deflection type instruments::

In these deflection types instruments, the deflection of the musical instrument provides a basis for determining the quantity under measurement.  The measured quantity produces some physical upshot with deflects are produces a mechanical deportation of the moving system of the instrument. An opposing effect is built in the instrument which tries to oppose the deflection or the mechanical deportation of the moving system. The opposing effect is closely related to the deflection or mechanical displacement which can exist direct observed. The opposing event is so designed that its magnitude increases with the increase of reflection or mechanical displacement of the moving organisation acquired past the quantity under measurement. The residue is achieved when opposing effect equals to cause producing the deflection or mechanical movement. The value of the measured quantity tin then be inferred from the deflection or mechanical deportation at the bespeak of balance. This is how deflection type instruments work.

two)Naught type instruments::

In these nada type instruments, a zip or null Indication leads to conclusion of the magnitude of measured quantity. In contrast to deflection blazon instruments, a null type instrument attempts to maintain the deflection at zero by suitable application of an effect opposing that generated past the measured quantity. Therefore for the  operation of a zero blazon instruments the following are required:

i) the effect produced by the measured quantity

two) the opposing effect whose value is accurately known. This is necessary in order to determine the numerical value of the measured quantity accurately

three) a detector which detect the null weather condition that is a device which indicates null deflection when the effect produced by the measured quantity is equal to the effect produced past the opposing quantity. The detector should be capable of displaying unbalance i.eastward., a condition when the upshot producer past the measured quantity is not equal to the opposing upshot.

            There is another mode in which electrical measuring instruments may be classified. This classification is based on the functions they perform. The three principal functions are explained below:

ane) Indicating function::

Instruments and Systems use different kinds of methods for supplying information apropos the variable quantity nether measurement. Most of the fourth dimension this information is obtained as a deflection of a pointer of a measuring musical instrument. In this way , the instrument performs a office which is known equally indicating part.

two) Recording role::

In many cases the instrument makes a written record usually on newspaper, of the value of the quantity under measurement confronting time or confronting some other variable. Thus this electrical instrument performs a recording office. For case, a potentiometric type of recorder used for monitoring temperature records the instantaneous values of temperatures on a strip nautical chart recorder.

three) Controlling role::

This is 1 of the almost important functions especially in the field of industrial control processes. In this case, information is used by the instrument or the arrangement to command the original measured quantity. Thus there are three main groups of electrical instruments. The largest group has the indicating office. Side by side in line is the group of instruments which have both indicating and recording functions. The concluding group falls into a special category and performs all the three functions i.e., indicating, recording and controlling.

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Source: https://www.electricalengineeringinfo.com/2016/03/types-electrical-measuring-instruments-absolute-secondary-instruments.html

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