# How to Read Voltage with the Help of a Digital Multimeter

Updated on November 3, 2014

## Methods of measuring voltages on a Digital Multimeter.

Measuring voltage is crucial for all realm of people ranging from Civil Engineers to Mechanical Engineers and Electrical Engineers. For example, If you are a student of Chemical Engineering, you might need to measure voltage from chemical cell reaction, and for Electrical Engineers, you may need check voltage from circuit. You will see two types of digital multimeter available in the market. One is manually switched which need to set knob manually, other is auto range that set the ranges automatically. In every Multimeter there are two probes, one is Red and other is Black. These two probes are connected through two PORTS, one is COM which stands for common or ground and other is mAVΩ, generally used for measuring current (A), voltage (V) or resistance(Ω).

Here, we will see how to measure voltage of a AA pencil battery (or AAA, C, D battery) . To begin with, place the red probe with mAVΩ and black probe in COM. For measuring DC voltage, set the multimeter knob at "2V" in DC voltage range. Place the Red probe in the positive(+) terminal of the cell and black (-) probe in the negative terminal of the cell. If other factors are okay, you should get 1.5V on the screen.

Majority of the devices generally have dc voltage source, you rarely need AC voltage source. To check AC voltage source you need to place the knob next to the DC voltage source. Now you might think what happen if you interchange the black probe into red probe. Straight forward answer, you will get negative reading on the multimeter. Since all the readings are based on with respect to ground, you will get 1.5V but negative polarity. Here, we define red probe as common or ground and black probe as negative terminal.

Circuits are very important in the breadboard. How to measure device voltage on breadboard? That gives you a clear idea if you need extra wiring or if there is any fault in your circuit diagram. To do this, place the knob at the range of 20V manually. Thats mean, 600V can measure voltage up to 600V. So if you set the knob at 600V, it will measure all voltages up to 600V. However if you set the range the range incorrectly, You might see "1" in the display. All modern digital mutimeter can able to measure overload current. To avoid it, please carefully set the ranges. This is a common question to all, how can I set knob to different ranges? To measure 15V in the multimeter you must set the knob within 20V, even if for 19.99V you must fix the knob to 20V. If you do not do so the display of your multimeter will probably show "1" as error.

Few important factors about measuring voltage:

• Voltage has polarity- If you place the red probe with negative terminal OR black probe with positive terminal, you will most probably get negative voltage and vice versa. Always consider the negative probe as reference voltage.
• Power up the circuit before reading voltage- If no voltage available in the circuit, you can not measure voltage by digital multimeter. The circuit must be powered up through an external voltage source to work.
• Do not confused AC voltage with DC voltage- Place the knob on the right voltage mode either on the straight line (DC) or on the sin wave line (AC).

Precautions Before using a Digital Multimeter:

Although all multimeters can measure AC current source, but it can be dangerous. It will not funny to test a electric ovens voltage through a multimeter. I recommend you to check DC or AC voltage through a AC tester before using your machine.

## Manual Digital Multimeter Vs Auto ranging Digital Multimeter

Manual Digital Multimeter
Auto Ranging Digital Multimeter
Need to set preset ranges before measuring values
No need to set Preset values
For measuring resistor, you need to know color codes for setting ohm ranges
No need to know color codes of resistors.
Cheap in Price
Expensive comparative to manual
Difference between Manual Digital Multimeter and Auto ranging Digital Multimeter

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## Popular

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• AUTHOR

4 years ago from Dhaka

Good. I wish if I transform multimeter into a car too..Thanks

• Besarien

4 years ago

No-no-no! I would expect the multimeter to transform into some sort of vehicle- at least a moped or something- if I spent 1500 dollars for it. I do like a good gadget but don't like spending money.

• AUTHOR