CLASSIFICATION

CLASSIFICATION DIFFERENTFORCES

CLASSIFICATION OF INSTRUMENTS  

• ABSOLUTE INSTRUMENTS  

These instruments give the magnitude of the quantity under measurement in terms of physical constants of the instrument.
Example : Tangent Galvanometer, Rayleigh,s current balance.

• SECONDARY INSTRUMENTS  

These instruments are so design that the quantity being measured can only be measured by observing the output indicating by the instrument.
Example : Voltmeter, Ammeter.

ACCORDING TO THE MODES OF OPERATION  

• ANALOG INSTUMENTS : 

The signals that vary in a continous fashion and take on an infinite number of values in agiven range are called analog signals and the devices taht produce analog signals are called analog devices.

• DIGITAL INSTRUMENTS : 

The signals which vary in discrete steps and thus take up only a finite number of values in a given range are called digital signals and the devices that produce digital signals are called digital devices.

ACCORDING TO THE METHOD USED FOR COMPARING THE UNKNOWN QUANTITY WITH THE UNIT OF MEASUREMENT  

Direct measuring instruments (example : ammeter , voltmeter )
Comparision instrument (example : AC and DC briges )

ACCORDING TO THE PRINCIPLE OF OPERATION  

➢ Magnetic effect
➢ Heating effect
➢ Electrostatic effect
➢ Electromagnetic effect
➢ Hall effect
➢ Thermal effect

*The instruments are also classified on the following catagories  

• INDICATING INSTRUMENTS  :

Indicating instruments are those instruments which indicate the magnitude of a quantity being measured.  They generally make use of a dial and pointer for this purpose.
They are classified in two catagories as Electro mechanical instruments and Electronic instruments.

• RECORDING INSTRUMENTS   :

Recording instruments give a continous record of the quantity being measured over a specified period.
The variations of the quantity being measured are recorded on a paper sheet fixed or moving by a pen.

• INTEGRATING INSTRUMENTS  :

Integrating instruments totalize events over a specified period of time.
Example : Ampere-hour and Watt-hour meter.