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,

radio Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...

clock A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...

watch A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...

, or

measuring instrument Instrumentation is a collective term for measuring instruments, used for indicating, measuring, and recording physical quantities. It is also a field of study about the art and science about making measurement instruments, involving the related ...

. Many scientific and industrial instruments use dials with pointers to indicate physical properties. 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 measuring instrument, instrument used to measure the electric current, current in a Electrical circuit, circuit. Electric currents are measured in amperes (A), hence the name. For direct measure ...

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

s and

hygrometer A hair tension dial hygrometer with a nonlinear scale. A hygrometer is an instrument that measures humidity: that is, how much water vapor is present. Humidity measurement instruments usually rely on measurements of some other quantities, such a ...

s, speedometers and

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

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 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 Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

. 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.

References

Measuring instruments {{Tool-stub

See also

References