Absolute instrument: These are instruments which read quantity under measurement indirectly i.e. in terms of deflection, degrees and meter constant e.g. tangent galvanometer
Secondary instrument: These instruments read the quantity under measurement directly at the time of measurement e.g. ammeter, voltmeter.
Absolute instruments: These instruments read the quantity under measurement indirectly i.e. in terms of deflection, degrees and meter constant. The actual value under measurement can be calculated by using the formula = deflection multiplied by constant of meter.
Examples of these instruments: 1) Tangent galvanometer. 2) Current balance meter.
Secondary instruments: These instruments read the quantity under measurement directly i.e. if it is ammeter, it reads directly in ampere e.g.
1) The meter is commonly used in lab such as ammeter, voltmeter, wattmeter and energy meter. 2) Secondary instruments are further classified as:
(a) Depending upon the principle of operation (b) Depending upon permissible percentage error. (c) Depending upon application.