Type of measuring Instrument

Type of instruments

  1. Absolute instrument 
  2. Secondary instrument


Absolute instrument :-

  • The instrument give the magnitude of the quantities and measurement in the term of physical constant of the instrument.

           Example:- Tangent galvanometer, Rayleigh's current balance.


Secondary instrument:- 

  • In this type of instrument the quantity being measured can only be measured by observing the output indicated by the instrument these instruments are calibrated by comparing with the absolute instrument.


Here Secondary instrument are again classified in three types that are following:-

  1. Indicating instruments
  2. integrating instruments 
  3. recording instruments

Indicating instrument :-

  • Indicating type of instrument which are indicate the magnitude of electrical quantity when it is being measured .
  • These indicating instrument given the output when the pointer moving the calibrated scale.
  • Indicating instruments are of second order instruments produce under-damped response having the practical value of  δ 0.6 to 0.8
Examples:- voltmeter, ammeter, watt meter, power factor meter

Integrating instruments:-

  • These are the instrument which measure or register by a set of Dials and pointers either the total quantity of electricity (In ampere-hours) or the total amount of electrical energy (in watt-hours) to a circuit in a given time."
Example:- Ampere hours meter , Energy meter

Recording instrument :-

  • The recording instrument which can continuously record the variation of the electrical quantity over a selected period of time.
  • In this type of recording instruments the moving system of the instrument carries a linked Pen which  rest lightly on a chart or graph , wrapped over a drum moving with slow uniform speed the movement of the drum is in a direction perpendicular to that of the pointer. The path traced out by the pen indicates the electrical quantity to be used or utilized.
  • So it can give the accurate result of consumption of electrical energy at any particular instant of time.
Example:- Galvanometer, graphic

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