A dial is generally a flat surface, circular or rectangular, with numbers or similar markings on it, used for displaying the setting or output of a

timepiece A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmi ...

clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and t ...

watch A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached b ...

, or

measuring instrument A measuring instrument is a device to measure a physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Est ...

. There are many instruments used in scientific and industrial applications that use dials with pointers as indicators of a specific physical property. Typical examples include pressure and vacuum gauges, fluid-level gauges (for fuel, engine oil, and so on),

voltmeter A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel. It usually has a high resistance so that it takes negligible current from the circuit. A ...

s and

ammeter An ammeter (abbreviation of ''Ampere meter'') is an instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. For direct measurement, the ammeter is connected in series with the circuit ...

thermometer A thermometer is a device that measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer ...

s and hygrometers, speedometers and

tachometer A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analo ...

s, and indicators (distance amplifying instruments). Traditionally these have been mechanical devices, but with the advent of electronic displays, analog dials are often simulated from digital measurements. The term may also refer to a movable

control knob {{more citations needed, date=January 2017 A control knob is a rotary device used to provide manual input adjustments to a mechanical/electrical system when grasped and turned by a human operator, so that differing extent of knob rotation corresp ...

used to change the settings of the controlled instrument, for example, to change the frequency of the radio, or the desired temperature on a thermostat. Styles of dials: * Circular, * Fixed pointer with moving scale, * Fixed scale with moving dial. Examples of dial usage: * Pressure and vacuum gauges, * Level gauges, * Volt and current meters, * Thermometers and thermostats (mechanical), * Speedometers and tachometers. ''Mirror dials'' are designed to reduce or eliminate the effect of parallax. They usually consist of a small mirrored strip running parallel to the graduations of the scale under the pointer. When the observer moves his position so that the pointer obscures the pointer's reflection in the mirror, an accurate reading may be taken.

See also