An analog device is one in which the output or display is a continuous function of time and bears a constant relation to its input.
The analog instruments ﬁnd extensive use in present-day applications although digital instruments are increasing in number and applications. The areas of application which are common to both analog and digital instruments are fairly limited at present.
Hence, it can safely be predicted that the analog instruments will remain in extensive use for a number of years and are not likely to be completely replaced by digital instruments for certain applications.
Classiﬁcation of Analog Instruments
Broadly, the analog instruments (and for that matter digital instruments) may be classiﬁed according to the quantity they measure. For example, an instrument meant for measurement of current is classiﬁed as an Ammeter while an instrument that measures voltage is classiﬁed as a Voltmeter. Thus we have wattmeters, power factor meters, frequency meters etc…
Electrical instruments may also be classiﬁed according to the kind of current that can be measured by them. Electrical instruments may be classiﬁed as instruments for:
- Direct Current (DC)
- Alternating Current (AC)
- Direct and Alternating Current (DC/AC)
- (a) Indicating
- (b) Recording,
- (c) Integrating.
- (i) electromechanical instruments,
- (ii) electronic instruments. ‘
- Direct Measuring Instruments
- Comparison Instruments