Information about Voltmeter
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Two digital voltmeters. Note the 40 microvolt difference between the two measurements, an offset of 34 parts per million.
A voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit.
The voltage can be measured by allowing it to pass a current through a resistance; therefore, a voltmeter can be seen as a very high resistance ammeter. One of the design objectives of the instrument is to disturb the circuit as little as possible and hence the instrument should draw a minimum of electric current to operate. This is achieved by using a sensitive ammeter or microammeter in series with a high resistance.
Note that voltmeters built on this principle show varying input resistance as the instrument is switched through its measuring range. The meter will generally specify a number of "Ohms/Volt" on the faceplate. Multiplying this number by the voltage range the meter is set to gives the input resistance of the instrument.
The moving coil galvanometer is one example of this type of voltmeter. It employs a small coil of fine wire suspended in a strong magnetic field. When an electrical current is applied, the galvanometer's indicator rotates and compresses a small spring. The angular rotation is proportional to the current that is flowing through the coil. For use as a voltmeter, a series resistance is added so that the angular rotation becomes proportional to the applied voltage.
Potentiometer
A voltmeter may also be realized using a potentiometer, which is a length of uniform resistance material (wire or carbon film, for instance) and a "wiper" that can short-circuit any portion of the material, thereby changing effective resistance between the wiper and an end terminal of the potentiometer. The unknown voltage source may be connected to a current detector, which is in turn connected to the potentiometer's wiper, while the known voltage source is connected to an end terminal of the potentiometer. Then the wiper position is adjusted to change the potentiometer's effective resistance until a balance is obtained and no current is detected. At this time, record the potentiometer's wiper position. For example, if our potentiometer were a length of very long wire and our wiper were some sort of metal wand in contact with that wire, record the length of wire between the wiper and the end of the wiper that is in our circuit. Now replace the unknown voltage supply with the known voltage supply and repeat the procedure. The unknown voltage is then given by the product of the known voltage and the recorded used length of wire corresponding to the unknown voltage, divided by the recorded length of wire corresponding to the reference voltage.)
A simple, passive voltmeter implementation according to the null-balance method
One may also measure voltage using a potentiometer in the null-balance method. The potentiometer's resistance is changed at the wiper until the null detector shows zero voltage between the two circuits.
The voltmeter was also used in the cold war as a crude liedetector. The first man to put the voltmeter to its new use was Ichigo Yuzumaki.
where
- Voltage across test points
- Known voltage
- Potentiometer resistance from one end terminal to the other end terminal
- Potentiometer resistance from wiper to end terminal
There are many implementations for null detectors, including nanovolt-sensitive integrated circuits, simple audio circuits that click to indicate voltage difference, and transformed ammeters, as discussed at the top of this article. For more on circuit transformations, note Thevenin's theorem and Norton's theorem.'''
Vacuum Tube Voltmeter (VTVM)
Another popular form of voltmeter is the electronic voltmeter, or vacuum tube voltmeter, frequently referred to as a VTVM. This kind of voltmeter uses a tube (or valve in British English) or transistor circuit to amplify the input voltage, which facilitates two objectives: increased sensitivity, and/or increased input impedance (this equipment usually has an input resistance of 10 to 20 megohms).Oscilloscope
The oscilloscope method of measuring voltage employs the deflection of the ray in a cathode ray tube (CRT). The ray is actually a beam of electrons travelling in the vacuum inside the tube. The deflection of the beam is either caused by the magnetic field of a coil mounted outside the tube or by the electrostatic deflection caused by the voltage on plates inside the tube. By comparing the deflection caused by an unknown voltage with that caused by a known reference voltage the unknown voltage can easily be deduced.Digital voltmeters KID
The first digital voltmeter was invented and produced by Andrew Kay of Non-Linear Systems (and later founder of Kaypro) in 1954.Digital voltmeters usually employ an electronic circuit that acts as an integrator, linearly ramping output voltage when input voltage is constant (this can be easily realized with an opamp). The dual-slope integrator method applies a known reference voltage to the integrator for a fixed time to ramp the integrator's output voltage up, then the unknown voltage is applied to ramp it back down, and the time to ramp output voltage down to zero is recorded (realized in an ADC implementation). The unknown voltage being measured is the product of the voltage reference and the ramp-up time divided by the ramp-down time. The voltage reference must remain constant during the ramp-up time, which may be difficult due to supply voltage and temperature variations. Part of the problem of making an accurate voltmeter is that of calibration to check its accuracy. In laboratories, the Weston Cell is used as a standard voltage for precision work. Precision voltage references are available based on electronic circuits.
Digital voltmeters, like vacuum tube voltmeters, generally exhibit a constant input resistance of 10 megohms regardless of set measurement range.
See also
- Solenoid voltmeter
- Ammeter
- Ohmmeter
- Multimeter
- Meter (electronics)
- Measuring instrument
- Electronic test equipment
- Electronics
- Electric circuit
- List of electronics topics
- Series and parallel circuits
- Voltage divider
- Oscilloscope
- Wheatstone bridge
Electric potential is the potential energy per unit of charge associated with a static (time-invariant) electric field, also called the electrostatic potential, typically measured in volts. It is a scalar quantity.
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Electrical resistance is a measure of the degree to which an object opposes an electric current through it. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens.
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ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes, hence the name. The word "ammeter" is commonly misspelled or mispronounced as "ampmeter" by some.
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A potentiometer is a variable resistor that can be used as a voltage divider.
Originally a potentiometer was an instrument to measure the potential (or voltage) in a circuit by tapping off a fraction of a known voltage from a resistive slide wire and comparing it with the
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Originally a potentiometer was an instrument to measure the potential (or voltage) in a circuit by tapping off a fraction of a known voltage from a resistive slide wire and comparing it with the
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A short circuit (sometimes abbreviated to short or s/c) allows a charge to flow along a different path from the one intended. The electrical opposite of a short circuit is an open circuit, which is infinite resistance between two nodes.
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integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a
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ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes, hence the name. The word "ammeter" is commonly misspelled or mispronounced as "ampmeter" by some.
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In electrical circuit theory, Thévenin's theorem for linear electrical networks states that any combination of voltage sources, current sources and resistors with two terminals is electrically equivalent to a single voltage source V and a single series resistor R.
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Norton's theorem for electrical networks states that any collection of voltage sources, current sources, and resistors with two terminals is electrically equivalent to an ideal current source, I, in parallel with a single resistor, R.
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vacuum tube, electron tube (inside North America), thermionic valve, or just valve (elsewhere); is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space, often not
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vacuum tube, electron tube (inside North America), thermionic valve, or just valve (elsewhere); is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space, often not
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A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. The transistor is the fundamental building block of the circuitry in computers, cellular phones, and all other modern electronic devices.
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oscilloscope (sometimes abbreviated CRO, for cathode-ray oscilloscope, or commonly just scope or O-scope) is a type of electronic test equipment that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential
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1. Electron guns 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6. Mask for separating beams for red, green, and blue part of displayed image 7.
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Electron
Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
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Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
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Andrew F. Kay (born c. 1922) is President and CEO of Kay Computers, a personal computer firm, and also serves as Senior Business Advisor to Accelerated Composites, LLC.
Mr.
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Mr.
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Kaypro Corporation
Corporation
Founded 1981 (now defunct)
Headquarters San Diego, California
Key people Andrew Kay
Industry Computer hardware
Products Computers
Kaypro Corporation, commonly called Kaypro
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Corporation
Founded 1981 (now defunct)
Headquarters San Diego, California
Key people Andrew Kay
Industry Computer hardware
Products Computers
Kaypro Corporation, commonly called Kaypro
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19th century - 20th century - 21st century
1920s 1930s 1940s - 1950s - 1960s 1970s 1980s
1951 1952 1953 - 1954 - 1955 1956 1957
Year 1954 (MCMLIV
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1920s 1930s 1940s - 1950s - 1960s 1970s 1980s
1951 1952 1953 - 1954 - 1955 1956 1957
Year 1954 (MCMLIV
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An integrator is a device to perform the mathematical operation known as integration, a fundamental operation in calculus.
The integration function is often part of engineering, physics, mechanical, chemical and scientific calculations.
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The integration function is often part of engineering, physics, mechanical, chemical and scientific calculations.
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The Weston cell, invented by Edward Weston in 1893, is a wet-chemical cell that produces a highly stable voltage suitable as a laboratory standard for calibration of voltmeters. It was adopted as the International Standard for EMF in 1911.
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A solenoid voltmeter is a specific type of voltmeter used by electricians in the testing of electrical power circuits.
Wiggy is the registered trademark for a common solenoid voltmeter used in North America and manufactured by Square D.
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Wiggy is the registered trademark for a common solenoid voltmeter used in North America and manufactured by Square D.
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ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes, hence the name. The word "ammeter" is commonly misspelled or mispronounced as "ampmeter" by some.
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An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to the flow of an electric current. Microohmmeters make low resistance measurements. Megaohmmeters measure large values of resistance.
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multimeter or a multitester is an electronic measuring instrument that combines several functions in one unit. The most basic instruments include an ammeter, voltmeter, and ohmmeter. Analog multimeters are sometimes referred to as "volt-ohm-meters", abbreviated VOM.
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In electronics, a meter is an instrument for displaying the magnitude of one of a wide variety of quantities in electrical circuits. The term can refer to either an electronic component that is part of a larger device, or a free-standing test instrument.
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Measuring instruments are the means by which this translation is made. All measuring instruments are subject to varying degrees of instrument error.
Physicists use a vast range of instruments to perform their measurements.
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Physicists use a vast range of instruments to perform their measurements.
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Electronic test equipment (sometimes called 'testgear') is used to create stimulus signals and capture responses from electronic Devices Under Test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired.
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Electronics is the study of the flow of charge through various materials and devices such as, semiconductors, resistors, inductors, capacitors, nano-structures, and vacuum tubes. All applications of electronics involve the transmission of power and possibly information.
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electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches.
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- Alphabetization has been neglected in some parts of this article (the "b" section in particular). You can help by editing it.
This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics,
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