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Published : 09/4/2018 10:35:50

The digital multimeter is an essential tool when you need to measure voltage, current, continuity, or resistance: this is why it is called multi-meter, multiple measurements. Many models are available on the market, from more professional ones, used by electricians, to simpler ones, ideal for a hobby users. Nevertheless, in any case you have to choose a precise and reliable model, so that you can carry out accurate and errorless measurements. Let’s now look at how this tool is made, how it works and how it is used.

How does a digital multimeter work?

Digital multimeters are is made by 3 parts:

  • A screen: usually it is a four digit screen. This is where the measurement values will be displayed. Some models have backlit screens and are, therefore, ideal to be used in low light conditions.
  • A selection handle: with it you can set up the multimeter according to the value you have to measure. Select A for current, V for voltage, and Ω for resistance.
  • Two jacks: with two feelers that can be switched out based on the type of measurement you need to make.

How is a digital multimeter made?

Every time you decide to use this tool to measure, you need to set it up correctly. Nevertheless, is you select the wrong setting, the tool will display either the number 1 or an error message, to let you know that the value you selected is too low, that it is overloaded, or out of range. Let’s now look at which measurements you can perform with a digital multimeter.

  • Measuring voltage

How do you use a digital multimeter when you need to measure voltage? First of all, we have to mention that alternating current can be very dangerous and a contactless tester is, therefore,  advised to measure it. In rare occasions it can also be measured with a multimeter, you need to set the handle on the V~ symbol (with the wavy dash). In order to measure the DC current, like the battery one, you need to set the handle on the V- symbol (with straight dash).

  • Measuring resistance

To measure resistance you need to select the resistance of reference, set the multimeter to 20k and keep the feelers on the resistor legs. At this point the tool will show the value of the actual resistance, or it will display 1 or 0.00. If you see 1 or OL on the screen, the tool is overloaded and you have to switch the value range to the higher one. On the other hand, if you see 0.00 you have to lower the setting via the handle.

Always remember that many resistances have a 5% tolerance: this means that each measurement you make with your tool could vary and could, in reality, be 5% higher or lower.

  • Measuring electrical current

Electrical current is one of the most complex measurements among the ones we are analyzing, because it has to be measured in series: this means that, while voltage is measured setting the feelers on VCG and GND in parallel, in order to measure the current the flow must be interrupted and the tool must be insert in series. In order to do so, you will have to extract the VCC wire to be placed on the resistance, and insert another one, then insert the feelers on both wires: this was you will be able to measure the current that is flowing in the multimeter on a breadboard, fundamental component when a circuit is being built.

  • Measuring continuity

Measuring the continuity with this kind of tool is useful to understand if the connections among circuit points have been created correctly and, therefore, if the circuit will function. How to use a digital multimeter to measure continuity? All you need to do is setting the handle to the symbol of a diode surrounded by propagation waves (it may be different on each tester but nonetheless easily recognizable): at this point, you need to touch with the feelers the points that you need to measure.

When you measure continuity, you test the resistance between two points: if there is low resistance, the points are connected with electric current and the multimeter will make a noise; if, on the other hand, there is higher resistance, the circuit is open, the points are not connected and the tester will not beep.

The digital multimeter is a fundamental tool if you need to take specific measurements like the aforementioned ones: besides being essential in electrical engineering labs, it could also be very useful when you need to set up an electric circuit in an office or a house. As we mentioned earlier, it is important to always opt for a highly professional model: this is the only way to make sure that you are taking correct measurements and you will be able to work in complete safety.

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