An instrument in which the value of ethnical quantity to be measured can be determined from the deflection of the instrument when it has been precalibrated by comparison with an absolute instrument
Right Answer is:
In a secondary instrument, the value of the ethnic quantity to be measured can be determined from the deflection of the instrument when it has been precalibrated by comparison with an absolute instrument.
In a broad sense, analog instruments may be classified into two ways:
- Absolute instruments
- Secondary instruments
Absolute instruments:- Absolute instruments give the value of the electrical quantity to be measured in terms of the constants of the instruments and to its deflection, no comparison with another instrument being required. For example, the tangent galvanometer gives the value of the current to be measured in terms of the tangent of the angle of deflection produced by the current, the radius and the number of turns of galvanometer coil, and the horizontal component of the earth’s magnetic fierce. No calibration of the instrument is thus necessary.
Secondary instruments:- Secondary instruments are so constructed that the value of current, voltage, or other quantity to be measured can be determined from the malefaction of the instruments, only if the latter has been calibrated by comparison with either an absolute instrument or one which has already been calibrated. The deflection obtained is meaningless until such calibration has been made.
This class of instruments is in most general use, the absolute instrument being seldom used except in standard laboratories and similar institutions.
The secondary instruments may be classified as
- Indicating instruments
- Recording instruments
- Integrating instruments
Indicating instruments are instruments which indicate the magnitude of a quantity being measured. They generally make use of a dial and a pointer for this purpose.
Recording instruments give a continuous record of the quantity being measured over a specified period. The variation of the quantity being measured is recorded by a pen Attache to the moving system of the instrument; the moving system is operated by the quantity being measured on a sheet of paper that moves perpendicular to the movement of the pen.
Integrating instruments record totalized events over a specified period of time. The summation, which they give, is the product of time and an electrical quantity. Ampere-hour and watt-hour (energy) meters are examples of this category.