How to use Digital Multimeter for measuring current, voltage and resistance?
Multimeter is a basic device but a lot of student don’t know how to operate correctly. This article will cover all basic function and use of a digital multimeter. A multimeter can use to diagnose electronic circuit, checking electronic component and to check battery health etc. So it is very important to know about basic operation of multimeter.
Actually in market there are two type of multimeter available Analog & digital multimeter. As in photo you can easily identified both multimeter. Now a day’s Analog multimeter is out dated and it is replaced by Digital Multimeter. So here we will cover basic function of a digital multimeter.
During work on electronic circuit the most basic thing is current and voltage measurement. By the help of these two elements (current and voltage) you can easily do your troubleshooting. Apart from current and voltage the third most important element is resistance. It also plays an important role in troubleshooting. So in this article we will discuss about measuring current, voltage and resistance. Also here we will cover “continuity test”.
Basically a multimeter is has three parts:
- Multimeter Display
- Its Selection Knob
- Its Ports and Probe wires
Digital Multimeter display has four digits and it also able to display negative values. Some multimeters have illuminated displays and back light option.
Its selection knob allows user to set the multimeter to measure different parameter such as milliamps (mA), DC or AC voltage (V) and resistance (Ω).
It’s Port and Probes are important part of a digital multimeter. Normally you will get three ports on a digital multimeter. These are COM, mAVΩ & 10A. Here COM stands for common or ground and is always connected with Ground or ‘-’ of a circuit. Normally in COM Port we use BLACK PROBE but both probes are similar and can use in any port. Its color is only for identification. 10A Port is a special port and it is used for large currents (greater than 200mA). mAVΩ Port is a very general port and used in 90% applications because in general we required multimeter for measuring only voltage & continuity in most of application and troubleshooting.
Continuity testing with multimeter
Basically continuity testing is used to identify correct wiring connection. Actually continuity testing is a resistance testing between two points of circuit. In a digital multimeter there is a speaker which gives a beep tone when we connect/short both led wire.
For continuity testing put one probe (Black) in COM port & other (Red) in mAVΩ Port. After it select multimeter Knob to continuity mode. Here you will find a speaker & Diode symbol. Connect these probes on circuit where you want to test continuity. If the resistance between these two points is less than few Ohm you will get a Beep tone.
Note: Before testing continuity ensure that there is no voltage on terminal. Try to check continuity when circuit is in power off condition.
Measuring Resistance with multimeter
Normally for electronic project a through hole resistor is used and in through hole resistor you will get its value by its “resister color code” or color band. But if you don’t know about its coding you can use multimeter for measuring resistor value.
For measuring resistor you have to use two port of multimeter (COM & mAVΩ). Put black cord on COM port & Red cord in mAVΩ port. After it select Ω segment by multimeter knob. Here you will find different ranges of resistance so select the correct range of multimeter. Don’t worry if you don’t know about resistance select higher range and then connect your resistance in probe. Now in multimeter Display either you will value 1 or actual resistance value. In cae you are getting 1 it means your multimeter is over load (may be in display you can get a OL symbol). So changer your multimeter knob one step higher probably you will get your resistance value.
There is one more possibility you may also get 0.00 values on display. It means for selected range it is approximate zero so for better accuracy select range towards lower side.
In many digital multimeters there is an auto selection mode so you should not worry about range selection.
Digital multimeters are very accurate so if your resistor value doesn’t match don’t worry, here your multimeter is correct. And also remember, many resistors have tolerance limit from 5% to 10%.
Measuring Voltage with multimeter
Voltage measurement with a digital multimeter is very easy. Only you have to remember few points so that you can operate it correctly. For measuring voltage put Black probe in COM port and Red probe in mAVΩ port. Now select multimeter knob in to voltage mode. You can also select AC or DC mode as per your requirement. And if in multimeter different ranges are available select as per your application. Now remember multimeter will always show a voltage difference from black probe to red probe. So keep black probe on circuit ground so that an exact voltage level can be display on multimeter.
Note: during measuring AC voltage keep your body away from live terminal. Even don’t touch metal part of multimeter probes.
Measuring Current with multimeter
Current measurement in any electronic circuit is very conceptual. Because current can measure if multimeter probes are connected in series in branch of circuit.
For measuring current with multimeter put Black probe in COM port & Red probe in mAVΩ port. But if you want to measure higher (more than 200mA) current, than put Red probe in 10A Port. Now remember connect these probe in a series connection. May be you have to disconnect one wire from circuit & put your multimeter probes in series. Select your multimeter knob in Current mode.
Hope that after reading this article you will be able to use your multimeter correctly.
So Enjoy Learning…..