1. Any of various measuring instruments for measuring a quantity.
2. Any of various devices designed to measure time, distance, speed, or intensity or indicate and record or regulate the amount or volume, as of the flow of a gas or an electric current.
3. Etymology: "a device for measuring"; from French -mètre used in combinations, from Latin metrum, "measure" or cognate Greek metron, "measure".

An instrument used to measure the amount of light transmitted through a transparent liquid or solid by means of a photocell or other light detector.

Any of various instruments used to measure the frequencies of sound waves that are audible to the human ear: Linda learned in her engineering class that one type of audio-frequency meters was a resonant-reed frequency meter.

1. An instrument that is used for measuring the magnitude of electric current flow.
2. A device which is used to measure the magnitude of an electric current of several amperes or more.

An ammeter is usually combined with a voltmeter and an ohmmeter in a multipurpose tool.

A tool that measures the integral (an essential part or whole), with respect to time, of the power in an electric circuit.

1. An instrument; such as, an ampere-hour meter, that measures electrical power and totals its measurement with time.
2. A device that measures electric power consumed, either at an instant, as in a wattmeter, or averaged over a time interval, as in a demand meter.

A demand meter is any of several types of instruments used to determine a customer's maximum demand for electric power over a time interval; generally it is used for billing industrial users.

A device that measures the complex ratio of voltage to current in a given circuit at a given frequency.

Any instrument which measures electrical resistance.

1. An instrument that measures the rate of flow (movement of electric charges, gases, liquids), without interruption of the flow, by producing an electromagnetic field in a liquid that creates an interior current, proportional to the actual flow rate, which is detected by two electrodes.
2. A flowmeter that offers no obstruction to liquid flow.

Two coils produce an electromagnetic field in the conductive moving fluid.

The current induced in the liquid, detected by two electrodes, is directly proportional to the rate of flow.

3. A flowmeter in which changes in the flow of blood are measured through impedance to electromagnetic lines of force that are introduced across a stream of blood.

It has the great advantage that an intact blood vessel can be used.

A meter that uses the resonant properties of mechanical devices to indicate frequency.

A type of monitor which is used to check a person's blood alcohol level as he or she blows through the mouthpiece of the meter.

The breath meter automatically measures the amount of alcohol which is present in one's body as the display signals whether the blood alcohol level is at or near the legal limit for driving.

1. An instrument which uses electronic devices; such as, amplifiers and limiters, to change an A.C. voltage into square waves before measuring its phase angle.
2. A phasemeter or a device for measuring the difference in phase of two alternating currents of electromotive forces which makes use of electronic devices; such as, amplifiers and limiters, that convert the alternating-current voltages being measured into square waves whose spacings are proportional to phase.

The limiters mentioned in the above definitions refer to electronic circuits that are used to prevent the amplitudes of electronic waveforms from exceeding specified levels while preserving the shapes of the waveforms at amplitudes less than the specified levels.

Also known as amplitude limiters; amplitude-limiting circuits; automatic peak limiters; clippers; clipping circuits; limiter circuits; and peak limiters.

An electronic device manufactured by the Church of Scientology at their Gold Base production facility: "Known as an "E-meter", the electropsychometer measures changes in the electrical resistance of the human body by inducing a tiny electrical current through it."

"The face of the electropsychometer has a galvanometer that indicates changes in the person's resistance. According to Scientology doctrine, the resistance corresponds to the mental mass and energy of the subject's mind, which changes when the individual thinks of particular mental images or engrams (unconscious, painful memories)."

"These concepts are not validated by other scientists outside of Scientology; the action of the E-meter is more commonly attributed to galvanic skin response, an effect that is used in lie detectors."

A meter with a movement consisting of fixed and movable metal plates, interleaved to form a capacitor.

The rotation of the movable plates is proportional to the DC or AC voltage applied across the capacitor.

1. A type of photometer that operates on the principle of artificially reducing the visibility of objects to threshold values (borderline of seeing and not seeing) and measuring the amount of the reduction on a standard scale.
2. An instrument; such as, a transmissometer (device used to measure the transmission of light through a medium), for making direct measurements of a visual range in the atmosphere or of the physical characteristics of the atmosphere which determine the visual range.
3. A photometric device for determining the range of visibility during daylight hours.

The measurement is made visually and the visibility meter is also used in lighting engineering for measuring the values of light (brightness) contrasts between an object and the background against which it is found or projected.

At meteorological stations visibility meters are used to measure the transparency of the atmosphere in a horizontal direction by measuring the contrast of a remote dark object; for example, a forest, against the background of the sky. There will be less contrast as the air transparency decreases.

The Système International [d'Unités] (International System [of Units]) derived unit of electric field strength; 1 volt/1 meter = 1 newton/1 coulomb.

An electrically operated instrument that indicates voltage standing-wave ratios and is calibrated in voltage ratios.

A device that measures the apparent power in an AC circuit.