A digital multimeter

A low cost digital multimeter

An analog benchtop multimeter

A 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. Digital multimeters are usually referred to as "digital-multi-meters", abbreviated DMM. Image File history File links Download high resolution version (672x800, 193 KB) Multimeter This image shows a digital multimeter. ... Image File history File links Download high resolution version (672x800, 193 KB) Multimeter This image shows a digital multimeter. ... low cost digital multimeter File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... low cost digital multimeter File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (1024x768, 301 KB){{PD-self]} File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (1024x768, 301 KB){{PD-self]} File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... This article is about the engineering discipline. ... Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea In physics and engineering, measurement is the activity of comparing physical quantities of real-world objects and events. ... Wire carrying current to be measured Spring providing restoring force An ammeter is a measuring instrument used to measure the flow of electric current in a circuit. ... Two digital voltmeters. ... An Ohmmeter is an electrical measuring instrument that measures electrical resistance, the opposition to the flow of an electric current. ...

A multimeter can be a handheld device useful for basic fault finding and field service work or a bench instrument which can measure to a very high degree of accuracy. Such an instrument will commonly be found in a calibration lab and can be used to characterise resistance and voltage standards or adjust and verify the performance of multi-function calibrators.

Current, voltage, and resistance measurements are considered standard features for multimeter. AVO multimeters, a manufacturer of early multimeters, derived their name from amperes, volts, and ohms, the units used for the measurement of current, voltage, and resistance. The Avometer was a British brand multimeter (USA). ... In electricity, current refers to electric current, which is the flow of electric charge. ... Josephson junction array chip developed by NIST as a standard volt. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ...

Multimeters are available in a wide ranges of features and prices (in the United States, inexpensive multimeters can be purchased for less than US$20). They are extremely handy devices to have around the house as they can be used to troubleshoot electrical problems in a wide array of household devices such as washing and drying machines, kitchen appliances, and even automobile electronics and electrical system.

Measured quantities

Contemporary equipment can measure many quantities besides voltage and resistance. Some common additional measured quantities and the units in which they are measured:

• Circuit continuity.
• Capacitance in farads.
• Frequency in hertz.
• Duty cycle as a percentage.
• Temperature in degrees Celsius or Fahrenheit.
• Conductance in siemens.
• Inductance in henrys.

A multimeter may be implemented with an analog meter deflected by an electromagnet, as a classic galvanometer; or with a digital display such as an LCD or vacuum fluorescent display. In fiction, continuity is consistency of the characteristics of persons, objects, places and events seen by the reader or viewer. ... Capacitors: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. ... Examples of various types of capacitors. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... The hertz (symbol: Hz) is the SI unit of frequency. ... In telecommunication and electronics, the term duty cycle has the following meanings: The duty cycle D is defined as the ratio between the pulse duration () and the period (T) of a rectangular waveform In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to... The percent sign A percentage is a way of expressing numbers as fractions of 100 and is often denoted using the percent sign, %. For example, 45. ... Fig. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Electrical conductance is the reciprocal of electrical resistance. ... The siemens (symbol: S) is the SI derived unit of electric conductance. ... An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... An inductor. ... It has been suggested that Tangent galvanometer be merged into this article or section. ... Reflective twisted nematic liquid crystal display. ... A vacuum fluorescent display (VFD) is a type of display used primarily on consumer-electronics equipment such as video cassette recorders. ...

Analog multimeters are not hard to find (though less common and often more expensive than low-end digital units), but are not considered as accurate as digital because of errors introduced in zeroing and reading the analog meter face.

Analog meters may be implemented with vacuum tubes to precondition and amplify the input signal. Such meters are known as vacuum tube volt meters (VTVM) or vacuum tube multimeters (VTMM).^[1]

Resolution

The resolution of a multimeter is often specified in "digits" of resolution. The use of a digit count dates back to the 1970's when multimeter vendors were very proud of how many digits their products could display (this was important, because readout displays were costly). The vendors started to specify the maximum resolution of the multimeter based on the digital display. For example, the term 5½ digits refers to the number of digits displayed on the readout of a multimeter.

By convention, a half digit can display either a zero or a one, while a three-quarters digit can display a numeral higher than a one but not nine. Commonly, a three-quarters digit refers to a maximum count of 3 or 5. The fractional digit is always the most significant digit in the displayed value. A 5½ digit multimeter would have five full digits that display values from 0 to 9 and one half digit that could only display 0 or 1. Such a meter could show positive or negative values from 0 to 199,999. A 3¾ digit meter can display a quantity from 0 to 3,999 or 5,999, depending on the manufacturer.

Accuracy

Similarly, better circuitry and electronics have improved meter accuracy. Older analog meters might have basic accuracies of five to ten percent. Modern portable DMMs may have accuracies as good provide calibration services after sales, as well, so that older equipment may be recertified.

Common features

Modern multimeters are most commonly digital, and identified by the term DMM or digital multimeter. In such an instrument, the signal under test is converted to a digital voltage and an amplifier with an electronically controlled gain preconditions the signal. Since the digital display directly indicates a quantity as a number, there is no risk of parallax causing an error when viewing a reading. A few analog units are available, however, and are sometimes considered better for detecting the rate of change of a reading; electronics expert Forrest Mims suggests keeping both analog and digital meters in one's toolbox, and the 2003 ARRL Handbook suggests that analog multimeters are often less susceptible to radio frequency interference. This does not adequately cite its references or sources. ... Forrest M. Mims III is the author of the Engineers Mini-Notebook–series of instructional books sold in Radio Shack and Tandy electronics stores. ... The ARRL Logo. ... It has been suggested that this article or section be merged with Radio waves. ...

The inclusion of solid state electronics, from a control circuit to small embedded computers, has provided a wealth of convenience features in modern digital meters. Commonly available measurement enhancements include:

• Autoranging, which selects the correct range for the quantity under test so that the most significant digits are shown. For example, a four-digit multimeter would automatically select an appropriate range to display 1.234 instead of 0.012, or overloading.

• Sample and hold, which will latch the most recent reading for examination after the instrument is removed from the circuit under test.

• Current-limited tests for voltage drop across semiconductor junctions. While not a replacement for a transistor tester, this facilitates testing diodes and a variety of transistor types.^[2][3]

• A graphic representation of the quantity under test, as a bar graph. This makes go/no-go testing easy, and also allows spotting of fast-moving trends.

• A continuity tester that beeps when a circuit conducts.

• A low-bandwidth oscilloscope.^[4]

• Automotive circuit testers, including tests for automotive timing and dwell signals.^[5]

• Simple data acquisition features to record maximum and minimum readings over a given period, or to take a number of samples at fixed intervals.^[6]

Digital meters often feature circuitry or software to accurately measure the AC voltage at any frequency. These meters integrate the input signal using the root mean square method, and will correctly read the true voltage of an input signal even if it is not a perfect sine wave. Significant figures (also called significant digits and abbreviated sig figs or sig digs, respectively) is a method of expressing errors in measurements. ... In electronics, a sample and hold circuit is used to interface real-world, changing analogue signals to a subsequent system such as an analog-to-digital converter. ... This article or section does not cite its references or sources. ... A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ... Transistor testers are instruments for checking transistors and solid-state diodes. ... Types of diodes closeup, showing germanium crystal In electronics, a diode is a component that restricts the direction of movement of charge carriers. ... A bar chart is a chart with rectangular bars of lengths usually proportional to the magnitudes or frequencies of what they represent. ... A Continuity tester, is an item of electrical test equipment used to determine if an electrical path can be established between two points ; that is if an electrical circuit can be made. ... Electrical conduction is the movement of electrically charged particles through a transmission medium (electrical conductor). ... A Tektronix model 475A portable analogue oscilloscope, a very typical instrument of the late 1970s. ... Data acquisition is the sampling of the real world to generate data that can be manipulated by a computer. ... In mathematics, the root mean square or rms is a statistical measure of the magnitude of a varying quantity. ...

Modern meters may be interfaced with a personal computer by IrDA links, RS-232 connections, USB, or an instrument bus such as IEEE-488. The interface allows the computer to record measurements as they are made or for the instrument to upload a series of results to the computer.^[7] The Infrared Data Association (IrDA) defines physical specifications communications protocol standards for the short range exchange of data over infrared light, for uses such as personal area networks (PANs). ... RS-232 (also referred to as EIA RS-232C or V.24) is a standard for serial binary data interchange between a DTE (Data terminal equipment) and a DCE (Data communication equipment). ... Note: USB may also mean upper sideband in radio. ... The Hewlett-Packard Instrument Bus (HP-IB), is a short-range digital communications cable standard developed by Hewlett-Packard (HP) in the 1970s for connecting electronic test and measurement devices (e. ...

As modern appliances and systems become more complicated, the multimeter is becoming less common in the technician's toolkit. More complicated and specialized equipment replaces it. Where a service man might have used an ohmmeter to measure resistance while testing an antenna, a modern technician may use a hand-held analyzer to test several parameters in order to determine the integrity of a network cable.^[8]

Probes

A multimeter can utilize a variety of test probes to connect to the circuit or device under test. Crocodile clips, retractable hook clips, and pointed probes are the three most common attachments. The connectors are attached to flexible, thickly-insulated leads that are terminated with connectors appropriate for the meter. Handheld meters typically use shrouded or recessed banana jacks, while benchtop meters may use banana jacks or BNC connectors. A test probe (test lead, test prod) is a physical device used to connect electronic test equipment to the device under test (DUT). ... A crocodile clip or alligator clip is a clip named for its resemblance to a crocodiles jaws. ... Stackable 4 mm banana plugs connected to a loudspeaker A banana connector (commonly banana plug for the male, banana jack for the female) is a single-wire (one conductor) electrical connector, widely used in science laboratories for temporarily joining wires to equipment. ... Male BNC connector Adapter between a female BNC connector and banana plugs The BNC connector is a type of RF connector used for terminating coaxial cable. ...

Meters which measure high voltages or current may use non-contact attachment mechanism to trade accuracy for safety. Clamp meters provide a coil that clamps around a conductor in order to measure the current flowing through it. A clamp meter (clamp-on ammeter) is a type of ammeter which measures electrical current without the need to disconnect the wiring through which the current is flowing. ...

See also

Electronics Portal

• Ammeter
• Ohmmeter
• Voltmeter
• anal sex

Image File history File links Nuvola_apps_ksim. ... Wire carrying current to be measured Spring providing restoring force An ammeter is a measuring instrument used to measure the flow of electric current in a circuit. ... An Ohmmeter is an electrical measuring instrument that measures electrical resistance, the opposition to the flow of an electric current. ... Two digital voltmeters. ... Roman men having anal sex. ...

References

1. ^ The Incomplete Idiot's Guide to VTVMs. tone-lizard.com. Retrieved on 2007-01-28.
2. ^ Hewes, John. Testing a diode with a multimeter. Retrieved on 2007-01-28.
3. ^ Goldwasser, Samuel. Basic Testing of Semiconductor Devices. Retrieved on 2007-01-28.
4. ^ Extech Instruments. Extech 5MHz Dual Channel Multiscope. Retrieved on 2007-01-28.
5. ^ Snap-on Incorporated. MT596AK Automotive Digital Multimeter. Retrieved on 2007-01-28.
6. ^ Extech Instruments. Extech Dual Channel, Datalogging multimeter. Retrieved on 2007-01-28.
7. ^ Fluke Manufacturing. Logging and analyzing events with FlukeView Forms Software. Retrieved on 2007-01-28.
8. ^ Fluke Manufacturing. Fluke DTX CableAnaylzer Series. Retrieved on 2007-01-28.

2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... January 28 is the 28th day of the year in the Gregorian calendar. ...

External links

Look up multimeter in
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• Operating a multimeter
• Basics of DMMs with summary of how to use them