"spark plugs in internal combustion engines. Spark-gap transmitters were used in early radio telegraph systems. Electrical breakdown Electrical breakdown or dielectric breakdown is when current flows through an electrical insulator when the voltage applied across it exceeds the breakdown voltage. This results in the insulator becoming electrically conductive. Electrical breakdown may be a momentary event (as in an electrostatic discharge), or may lead to a continuous arc if protective devices fail to interrupt the current in a power circuit. Under sufficient electrical stress, electrical breakdown can occur within solids, liquids, gases or vacuum. However, the specific breakdown mechanisms are different"
"hours) 0.03%, thermal EMF 0.1 μV/°C, noise −42 dB, voltage coefficient 0.1 ppm/V, inductance 0.08 μH, capacitance 0.5 pF. An ammeter shunt is a special type of current-sensing resistor, having four terminals and a value in milliohms or even micro-ohms. Current-measuring instruments, by themselves, can usually accept only limited currents. To measure high currents, the current passes through the shunt across which the voltage drop is measured and interpreted as current. A typical shunt consists of two solid metal blocks, sometimes brass, mounted on an insulating base. Between the blocks, and soldered or brazed to them, are one or more"
"an example of the iron vane type, used for measuring large AC currents up to 1000 amperes. The iron jaws of the meter direct the magnetic field surrounding the conductor to an iron vane that is attached to the needle of the meter. The iron vane moves in proportion to the strength of the magnetic field, and thus produces a meter indication proportional to the current. This type of ammeter can measure both AC and DC currents and provides a true RMS current measurement of non-sinusoidal or distorted AC waveforms. Interchangeable meter movements can be installed in the clamping assembly"
"Amperometry Amperometry in chemistry is detection of ions in a solution based on electric current or changes in electric current. Amperometry is used in electrophysiology to study vesicle release events using a carbon fiber electrode. Unlike patch clamp techniques, the electrode used for amperometry is not inserted into or attached to the cell, but brought in close proximity of the cell. The measurements from the electrode originate from an oxidizing reaction of a vesicle cargo released into the medium. Another technique used to measure vesicle release is capacitive measurements. Electrochemical or amperometric detection as it was first used in ion"
"W/V. Current can be measured by a multimeter, a device that can measure electrical voltage, current, and resistance. The standard ampere is most accurately realized using a Kibble balance, but is in practice maintained via Ohm's law from the units of electromotive force and resistance, the volt and the ohm, since the latter two can be tied to physical phenomena that are relatively easy to reproduce, the Josephson junction and the quantum Hall effect, respectively. At present, techniques to establish the realization of an ampere have a relative uncertainty of approximately a few parts in 10, and involve realizations of"
"Ampere The ampere (; symbol: A), often shortened to ""amp"", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current. The earlier CGS measurement system had two different definitions of current, one essentially the same as the SI's and the other using electric charge as the base unit, with the unit of charge defined by"
"Amperometric titration Amperometric titration refers to a class of titrations in which the equivalence point is determined through measurement of the electric current produced by the titration reaction. It is a form of quantitative analysis. A solution containing the analyte, A, in the presence of some conductive buffer. If an electrolytic potential is applied to the solution through a working electrode, then the measured current depends (in part) on the concentration of the analyte. Measurement of this current can be used to determine the concentration of the analyte directly; this is a form of amperometry. However, the difficulty is that"
"Typical circuit breakers will provide 16 A. The current drawn by a number of typical appliances are: Ampere The ampere (; symbol: A), often shortened to ""amp"", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current. The earlier CGS measurement system had two different definitions of current, one essentially the same as the SI's"
"Atmometer An ""atmometer or evaporimeter""' is a scientific instrument used for measuring the rate of water evaporation from a wet surface to the atmosphere. Atmometers are mainly used by farmers and growers to measure evapotranspiration (ET) rates of crops at any field location. Evapotranspiration is a measure of all of the water that evaporates from land surfaces plus the water that transpires from plant surfaces. Based on the amount of water that does evaporate and transpire, the user can water crops correspondingly, which results in less water use and possibly increased crop yields. Companies that currently sell atmometers include C&M"
"Ohmmeter An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current. Micro-ohmmeters (microhmmeter or microohmmeter) make low resistance measurements. Megohmmeters (also a trademarked device Megger) measure large values of resistance. The unit of measurement for resistance is ohms (Ω). The first ohmmeters were based on a type of meter movement known as a 'ratiometer'. These were similar to the galvanometer type movement encountered in later instruments, but instead of hairsprings to supply a restoring force they used conducting 'ligaments'. These provided no net rotational force to the movement. Also, the movement was wound with"
"on it. This can be somewhat misleading as it may be confused for an indicator of a bad battery when in reality it indicates a problem with the vehicle's charging system. Alternatively, an ammeter may be fitted. This indicates whether the battery is being charged or discharged. In the adjacent picture, the ammeter is marked ""Alternator"" and the symbols are ""C"" (charge) and ""D"" (discharge). Both ammeters and voltmeters individually or together can be used to assess the operating state of an automobile battery and charging system. A battery indicator is a feature of many electronic devices. In mobile phones,"
"from 1 to 100 centi-amperes, the deci-ampere balance from 1 to 100 deci-amperes, the ampere balance from 1 to 100 amperes, etc. Ampere balance The ampere balance (also current balance or Kelvin balance) is an electromechanical apparatus used for the precise measurement of the SI unit of electric current, the ampere. It was invented by William Thomson, 1st Baron Kelvin. The current to be measured is passed in series through two coils of wire, one of which is attached to one arm of a sensitive balance. The magnetic force between the two coils is measured by the amount of weight"
"Ampere hour An ampere hour or amp hour (symbol Ah; also denoted A⋅h or A h) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3600 coulombs. The commonly seen ""milliampere hour"" (mAh or mA⋅h) is one-thousandth of an ampere hour (3.6 coulombs). The ampere hour is frequently used in measurements of electrochemical systems such as electroplating and for battery capacity where the commonly known nominal voltage is dropped. A ""milliampere second"" (mA⋅s) is a unit of measure"
"Ampere balance The ampere balance (also current balance or Kelvin balance) is an electromechanical apparatus used for the precise measurement of the SI unit of electric current, the ampere. It was invented by William Thomson, 1st Baron Kelvin. The current to be measured is passed in series through two coils of wire, one of which is attached to one arm of a sensitive balance. The magnetic force between the two coils is measured by the amount of weight needed on the other arm of the balance to keep it in equilibrium. This is used to calculate the magnitude of the"
"Abampere The abampere (abA), also called the biot (Bi) after Jean-Baptiste Biot, is the basic electromagnetic unit of electric current in the emu-cgs system of units (electromagnetic cgs). One abampere is equal to ten amperes in the SI system of units. An abampere of current in a circular path of one centimeter radius produces a magnetic field of 2π oersteds at the center of the circle. The emu-cgs (or ""electromagnetic cgs"") units are one of several systems of electromagnetic units within the centimetre gram second system of units; others include esu-cgs, Gaussian units, and Lorentz–Heaviside units. In these other systems,"
"a passive electromechanical device, namely a 200 µA DC d'Arsonval movement ammeter fed from a full-wave copper-oxide rectifier mounted within the meter case. The mass of the needle causes a relatively slow response, which in effect integrates the signal, with a rise time of 300 ms. 0 VU is equal to +4 dBu, or 1.228 volts RMS, a power of about 2.5 milliwatts when applied across a 600-ohm load. 0 VU is often referred to as ""0 dB"". The meter was designed not to measure the signal, but to let users aim the signal level to a target level of"
"Multimeter A multimeter or a multitester, also known as a VOM (volt-ohm-milliammeter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance. Analog multimeters use a microammeter with a moving pointer to display readings. Digital multimeters (DMM, DVOM) have a numeric display, and may also show a graphical bar representing the measured value. Digital multimeters are now far more common due to their cost and precision, but analog multimeters are still preferable in some cases, for example when monitoring a rapidly varying value. A multimeter can be a"
"Wattmeter The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. The traditional analog wattmeter is an electrodynamic instrument. The device consists of a pair of fixed coils, known as ""current coils"", and a movable coil known as the ""potential coil"". The current coils are connected in series with the circuit, while the potential coil is connected in parallel. Also, on analog wattmeters, the potential coil"
"These studies show that atmometers are especially useful for areas that do not have access to nearby weather stations and/or evapotranspiration data. Atmometer An ""atmometer or evaporimeter""' is a scientific instrument used for measuring the rate of water evaporation from a wet surface to the atmosphere. Atmometers are mainly used by farmers and growers to measure evapotranspiration (ET) rates of crops at any field location. Evapotranspiration is a measure of all of the water that evaporates from land surfaces plus the water that transpires from plant surfaces. Based on the amount of water that does evaporate and transpire, the user"
"permanent magnet moves the needle. Moving magnet Ammeters are able to carry larger currents than moving coil instruments, often several tens of Amperes, because the coil can be made of thicker wire and the current does not have to be carried by the hairsprings. Indeed, some Ammeters of this type do not have hairsprings at all, instead using a fixed permanent magnet to provide the restoring force. An electrodynamic movement uses an electromagnet instead of the permanent magnet of the d'Arsonval movement. This instrument can respond to both alternating and direct current and also indicates true RMS for AC. See"
"Automatic meter reading Automatic meter reading (AMR) is the technology of automatically collecting consumption, diagnostic, and status data from water meter or energy metering devices (gas, electric) and transferring that data to a central database for billing, troubleshooting, and analyzing. This technology mainly saves utility providers the expense of periodic trips to each physical location to read a meter. Another advantage is that billing can be based on near real-time consumption rather than on estimates based on past or predicted consumption. This timely information coupled with analysis can help both utility providers and customers better control the use and production"
"any of the interconnected devices. Battery powered test equipment may be the safest choice in such situations. Meters intended for testing in hazardous locations or for use on blasting circuits may require use of a manufacturer-specified battery to maintain their safety rating. Multimeter A multimeter or a multitester, also known as a VOM (volt-ohm-milliammeter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance. Analog multimeters use a microammeter with a moving pointer to display readings. Digital multimeters (DMM, DVOM) have a numeric display, and may also show"
"Voltameter A voltameter or coulometer is a scientific instrument used for measuring quantity of electricity (electric charge) through electrolytic action. The SI unit of quantity of electricity is the coulomb. The voltameter should not be confused with a voltmeter, which measures electric potential. The SI unit for electric potential is the volt. The voltameter is an electrolytic cell and the measurement is made by weighing the element deposited or released at the cathode in a specified time. This is the most accurate type. It consists of two silver plates in a solution of silver nitrate. When current is flowing, silver"
"it is connected; most are marked with a positive terminal, but some have centre-zero mechanisms and can display currents in either direction. A moving coil meter indicates the average (mean) of a varying current through it, which is zero for AC. For this reason moving-coil meters are only usable directly for DC, not AC. This type of meter movement is extremely common for both ammeters and other meters derived from them, such as voltmeters and ohmmeters. Moving magnet ammeters operate on essentially the same principle as moving coil, except that the coil is mounted in the meter case, and a"
"consumed. Wattmeter The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements. The traditional analog wattmeter is an electrodynamic instrument. The device consists of a pair of fixed coils, known as ""current coils"", and a movable coil known as the ""potential coil"". The current coils are connected in series with the circuit, while the potential coil is connected in parallel. Also, on analog wattmeters, the potential"
"ammeter gives reading equal to the rated current of the HV side. After reaching at rated current of HV side, all three instruments reading (Voltmeter, Ammeter and Watt-meter readings) are recorded. The ammeter reading gives the primary equivalent of full load current IL. As the voltage applied for full load current in short circuit test on transformer is quite small compared to the rated primary voltage of the transformer, the iron losses in transformer can be taken as negligible here. To conduct a short-circuit test on power transformer: formula_1 is the full-load copper loss formula_2is the applied voltage formula_3 is"
"ArDM The ArDM (Argon Dark Matter) Experiment is a particle physics experiment based on a liquid argon detector, aiming at measuring signals from WIMPs (Weakly Interacting Massive Particles), which probably constitute the Dark Matter in the universe. Elastic scattering of WIMPs from argon nuclei is measurable by observing free electrons from ionization and photons from scintillation, which are produced by the recoiling nucleus interacting with neighbouring atoms. The ionization and scintillation signals can be measured with dedicated readout techniques, which constitute a fundamental part of the detector. In order to get a high enough target mass the noble gas argon"
"Other instruments—essentially similar, but with higher sensitivity—are used for accurate measurements of very small or very large quantities. These include nanovoltmeters, electrometers (for very low currents, and voltages with very high source resistance, such as 1 TΩ) and picoammeters. Accessories for more typical multimeters permit some of these measurements, as well. Such measurements are limited by available technology, and ultimately by inherent thermal noise. Analog meters can measure voltage and current by using power from the test circuit, but require a supplementary internal voltage source for resistance testing, while electronic meters always require an internal power supply to run their"
"amplifier""; its main purpose is to reduce the electrical load on the small signals (in the mV range) produced by cells so that they can be accurately recorded by low-impedance electronics. The amplifier increases the current behind the signal while decreasing the resistance over which that current passes. Consider this example based on Ohm's law: A voltage of 10 mV is generated by passing 10 nanoamperes of current across 1 MΩ of resistance. The electrometer changes this ""high impedance signal"" to a ""low impedance signal"" by using a voltage follower circuit. A voltage follower reads the voltage on the input"
"The electrode is held at a positive potential, and when the cargo from a fused vesicle is near the electrode, oxidation of the cargo transfers electrons to the electrode. This causes a spike, the size of which can be used to estimate the number of vesicles, and the frequency gives information about the release probability. Amperometry Amperometry in chemistry is detection of ions in a solution based on electric current or changes in electric current. Amperometry is used in electrophysiology to study vesicle release events using a carbon fiber electrode. Unlike patch clamp techniques, the electrode used for amperometry is"
"Ampère was elected a Foreign Member of the Royal Society and in 1828, a foreign member of the Royal Swedish Academy of Science. In recognition of his contribution to the creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity, established the ampere as a standard unit of electrical measurement, along with the coulomb, volt, ohm, and watt, which are named, respectively, after Ampère's contemporaries Charles-Augustin de Coulomb of France, Alessandro Volta of Italy, Georg Ohm of Germany, and James Watt of Scotland. Ampère's name is one of the 72 names inscribed on the"
"is present. As most electromagnetic fields encountered in everyday situation are those generated by household or industrial appliances, the majority of EMF meters available are calibrated to measure 50 and 60 Hz alternating fields (the frequency of European and US mains electricity). There are other meters which can measure fields alternating at as low as 20 Hz, however these tend to be much more expensive and are only used for specific research purposes. Active sensors are sensing devices which contain active components; usually this solution allows for a more precise measurement with respect to passive components. In fact, a passive"
"to the resistor. A simple ohmmeter may apply a voltage from a battery across the unknown resistor (with an internal resistor of a known value in series) producing a current which drives a meter movement. The current, in accordance with Ohm's law, is inversely proportional to the sum of the internal resistance and the resistor being tested, resulting in an analog meter scale which is very non-linear, calibrated from infinity to 0 ohms. A digital multimeter, using active electronics, may instead pass a specified current through the test resistance. The voltage generated across the test resistance in that case is"