What is a Multi-meter?

What is a Multi-meter?

 Where to Use It and When?

A multi-meter or Volt-Ohm meter, is a device used to measure voltage, current and resistance. Multimeter might be analog type multimeters or digital multimeters, depending on the type of circuit being used. Normally, these hand-held devices are very useful to detect faults or provide field measurements at a high degree of accuracy. They are one of the preferred tools by electricians to troubleshoot electrical problems on motors, appliances, circuit, power supplies, and wiring systems
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Analog multi-meter is based on a micro ammeter that moves over a scale. Analog multi-meters although cheap, can be very difficult to read accurately, and they must be handled carefully, because of you drop the meter, you are likely to damage it. Analog multi-meter are not accurate as a digital meter, when you are trying to use it as a voltmeter; however, analog multi-meters are great detecting slow voltage changes, as you will the see the needle moving over the scale.

Digital multi-meters are designed for electronics engineers, so many multi-meters, might contain features that probably you will not need ever. Digital meters will provide their output on a LCD screen, and might cost more than analog multi meters.

By turning the central knob, you will be selecting the appropriate type of measurement you will me making. For example when it is set to 20V DC, it means that 20 volts will be the maximum voltage that can be measured, normally ideal for all circuits that you will build. If you would like to measure smaller voltages then you should set your digital multi-meter to the 2V or 200mV selection.

The digital multimeter is better when it is used as a voltmeter, because it resistance is much higher, 1 M or 10 M, compared to 200 for an analogue multimeter on a similar range. Occasionally, a digital multimeter will show voltage present when a circuit should not be energized. The question is whether it's real and potentially dangerous voltage, or merely 'Ghost Voltage.' This kind of voltage is caused when energized circuits and non-energized wiring are located in close proximity to each other.
Multi-meter are capable of providing several measurements and tests; however most multi-meters can record the following:

Direct Voltage
Alternating Current
Direct Current
Resistance in Ohms
Capacity (farads)
Conductance (Siemens)
Decibels
Duty cycle, measure as a percentage
Frequency (Hz)
Inductance (henrys)
Temperature Celsius or Fahrenheit, only certain models and with special equipment
Light level
Acidity
Alkalinity
Wind Speed
Relative Humidity
Many multimeter manufacturers have additional features that can be added when you are purchasing your new device, so be sure to read and verify your needs so you can end up with the proper equipment.

Analog multimeters are becoming obsolete as they are being replaced by digital multimeters.

Analog Multi-meters:

The best way to use an analog multi meter is when it is set as an ammeter, due to their low resistance and high sensitivity, with scales down to 50µA.

Digital Multi-meters:

Multi-meter Functions:

Alternating Voltage

Other sensors could be attached to multi-meters making them able to record measurements of:

Light level
Acidity
Alkalinity
Wind Speed
Relative Humidity
Many multimeter manufacturers have additional features that can be added when you are purchasing your new device, so be sure to read and verify your needs so you can end up with the proper equipment

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Multimeter