What is a Multimeter?
A multimeter 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 electrician to troubleshoot electrical problems on motors, appliances, circuit, power supplies, and wiring systems. Analog multimeters are becoming obsolete as they are being replaced by digital multimeters.
Analog multimeter is based on a micro ammeter that moves over a scale. Analog multimeters 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 multimeter are not accurate as a digital meter, when you are trying to use it as a voltmeter; however, analog multimeters are great detecting slow voltage changes, as you will the see the needle moving over the scale.
The best way to use an analog multimeter is when it is set as an ammeter, due to their low resistance and high sensitivity, with scales down to 50µA.
Digital multimeters are designed for electronics engineers, so many multimeters, 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 multimeters. 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 multimeter 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.
Multimeters are capable of providing several measurements; however most multimeters can record the following:
- Alternating Voltage,
- Direct Voltage
- Alternating Current
- Direct Current
- Resistance in Ohms
- Capacity (farads)
- Conductance (Siemens)
- Duty cycle, measure as a percentage
- Frequency (Hz)
- Inductance (henrys)
- Temperature Celsius or Fahrenheit, only certain models and with special equipment
- Light level
- Wind Speed
- Relative Humidity
Many multimeter manufacturers have additional features that can be added when you are purchasing your multimeter, so be sure to read and verify your needs so you can end up with the proper equipment.