What is Digital Multimeter in English Articletopjankari.com

What is Digital Multimeter in English Article

What is Digital Multimeter in English Article.

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 Digital Multimeter~~

Digital multimeters sometimes abbreviated (DMM or DVOM) display the measured value in numerals, and may also display a bar of a length proportional to the quantity being measured.  Digital multimeters are now far more common than analog ones, but analog multimeters are still  preferable in some cases, for example when monitoring a rapidly-varying value. A multimeter can be a hand-held device useful for basic fault finding and field service work, or a bench instrument which can measure to a very high degree of accuracy. They can be used to trou- bleshoot electrical problems in a wide array of industrial and household devices such as electronic  equipment, motor controls, domestic appliances, power supplies, and wiring systems. 

 

Quantities measured by Digital multimeter~~ 

 

Modern multimeters can measure many quantities. The common ones are:

~Voltage: alternating and direct, in volts.

~ Current:  alternating and direct, in amperes.

~ Resistance, in ohms.

~ Duty cycle as a percentage. 

~ Frequency in hertz.

~ Inductance in henrys.

 

The frequency range for which AC measurements are accurate must be specified.

Additionally, some multimeters measure:

~ Capacitance in farads.

~ Conductance in siemens.

Decibels.

~ Digital multimeters may also include circuits for:

~ Continuity tester; sounds when a circuit conducts

~ Diodes (measuring forward drop of diode junctions), and transistors (measuring current gain and other parameters) 

~ Battery checking for simple 1.5 volt and 9 volt batteries. This is a current loaded voltage scale which simulates in-use voltage measurement. 

Modern multimeters are often digital due to their accuracy, durability and extra features. In a digital multimeter the signal under test is converted to a voltage and an amplifier with electronically controlled gain preconditions the signal. A digital multimeter displays the quantity measured as a number, which eliminates parallax errors. 

Modern digital multimeters may have an embedded computer, which provides a wealth of con- venience features. Measurement enhancements available include: 

 

~ Auto-ranging, 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. Auto-ranging meters usually include a facility to hold the meter to a particular range, because a measure- ment that causes frequent range changes can be distracting to the user. Other factors being equal, an auto-ranging meter will have more circuitry than an equivalent non-auto-ranging meter, and so will be more costly, but will be more convenient to use. 

 

~ Auto-polarity for direct-current readings, shows if the applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads). 

 

 

~ 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.

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

Summary~

A Multimeter is also used to check for AC or DC voltage, resistance or continuity of electrical components and small amounts of current in circuits.

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The frequency range for which AC measurements are accurate must be specified.

Additionally, some multimeters measure:

~ Capacitance in farads.

~ Conductance in siemens.

Decibels.

~ Digital multimeters may also include circuits for:

~ Continuity tester; sounds when a circuit conducts

~ Diodes (measuring forward drop of diode junctions), and transistors (measuring current gain and other parameters) 

~ Battery checking for simple 1.5 volt and 9 volt batteries. This is a current loaded voltage scale which simulates in-use voltage measurement. 

Modern multimeters are often digital due to their accuracy, durability and extra features. In a digital multimeter the signal under test is converted to a voltage and an amplifier with electronically controlled gain preconditions the signal. A digital multimeter displays the quantity measured as a number, which eliminates parallax errors. 

Modern digital multimeters may have an embedded computer, which provides a wealth of con- venience features. Measurement enhancements available include: 

 

~ Auto-ranging, 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. Auto-ranging meters usually include a facility to hold the meter to a particular range, because a measure- ment that causes frequent range changes can be distracting to the user. Other factors being equal, an auto-ranging meter will have more circuitry than an equivalent non-auto-ranging meter, and so will be more costly, but will be more convenient to use. 

 

~ Auto-polarity for direct-current readings, shows if the applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads). 

 

 

~ 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.

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

Summary~

A Multimeter is also used to check for AC or DC voltage, resistance or continuity of electrical components and small amounts of current in circuits.

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