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The name of the instrument itself suggests that a multimeter is used to measure more than one quantity. Usually multimeters measure the following quantities:
- Alternating Current or Direct Current
- Alternating Current or Direct Current voltages
There are two types of multimeters commonly in use:
- Analog Multimeter
- Digital Multimeters
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This type of a multimeter is basically a moving coil instrument. A rectifier unit is also provided with the instrument. It is a multiranged instrument and various ranges are obtained by different resistance elements in series or in parallel with the movement of the instrument. With the help of a rotary selector switch, the various ranges are used. Usually different ranges used are somewhat similar to those given below:
- Current Ranges : 0-1A 0-5A. 0-10A
- Voltage ranges : 0-10V 0-50V 0-150V 0-500V 0-1000V
- Resistance ranges : 0-1Ω 0-10Ω 0-100Ω 0-1000Ω
Some multimeters are provided with additional equipment known as a current transformer. With the help of this transformer, currents up to 400A can be measured. Such a multimeter is known as a tong or a clamp-on tester. An analog multimeter is a compact and portable instrument and therefore is very popularly used in practice.
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The digital multimeter (DMM) is an instrument capable of measuring DC voltage, AC voltage, AC current, DC current, resistance, conductance, and decibels. The digital multimeter offers increased versatility. Some DMM's can measure temperature, frequency, etc. These days DMM's are popularly used and they have almost entirely replaced analog multimeters.
A DMM has a digital display and a function selector switch. The range selection takes place automatically. There are four input terminals, out of which two terminals are used for measurements of all the general purpose quantities such as AC/DC voltage, resistance, capacitance and diode and transistor testing.These terminals are not used for current measurements.The ranges that a DMM can calculate is given below:
- DC Voltages - Five voltage ranges are available.The voltage range is from 200mV to 1000V. Accuracy is about ~+mn~ 0.03% and resolution is about 10μV.
- AC Voltages - Five voltage ranges are available ranging from 200mV to 750V. Accuracy is dependent on frequency. Best accuracy obtained is about 0.5%. Resolution is about μV.
- Resistance - The resistance range is from 200 Ω to 20 MΩ. Accuracy is about ~+mn~ 0.1% of reading.
- DC Current - Five ranges available from 200 μA to 2000 mA. Accuracy is about ~+mn~ 0.3% of reading. Resolution is about ~+mn~ 0.01 μA.
- AC Current - Five ranges available from 200 μA to 2 ampere. Accuracy is dependent on frequency. Best accuracy obtained is about ~+mn~ 1%.
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Comparison between Anaolg Multimeters and Digital Multimeters
Here are the main points of comparison between the two.
In analog multimeters, visual indication of changes in the reading is not good due to the effect of damping torque. Whereas in a digital multimeter, an excellent visual indication of changes in reading is acquired.
Analog multimeters are accurate, but not as much as the digital multimeter due to the magnetic effect in the coil being degraded after usage. Digital multimeters are highly accurate compared to analog.
An analog multimeter is less costly compared to the digital counterpart due to a simple construction and no power supply being required. But in the case of a digital multimeter, it is far more expensive than the analog multimeter and has a complicated construction, and also requires a power supply.
In an analog multimeter, the range has to be adjusted by the user. Whereas in a digital multimeter, the range is adjusted automatically.
In a digital multimeter, the mechanical handle can be easily rotated to tune the circuit to its peak.
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Which is Best to Use?
Considering the points mentioned above, I personally would prefer the digital multimeter for its high accuracy and more sleek nature. I hope this article proves to be informative if you are going in to buy a multimeter.