Use a Digital Multimeter: Some products of technology can be overwhelming to get at first but once it’s working and usage is understood, it becomes a great asset in the hands of the user.
A digital multimeter is a similar electronic device seemingly complex but of great usage! It is a handheld device used to measure 2 or more electrical values-primarily voltage, current, and resistance;
And is widely used by technicians in the electrical and electronic industries. However, it can be useful to have one at home too and know some of the basics of the device.
Some Basics of the Digital Multimeter:
• A digital multimeter comes with 2 thick red and black wires which are called the positive and negative probes respectively.
• The red probe is always connected to the positive end and the black probe to the negative end.
• Below the display screen on the multimeter itself is a dial that rotates around and is encircled by different segments of features.
• Various segments in the digital multimeter are used for measuring DC voltage, resistance, continuity, the current gain of the transistor, ampere current, AC voltage, etc.
• Other than this, there are 3 consecutive ports in the digital multimeter marked as COM, v(ohm)mA, and 10A.
• The black probe is always inserted into the COM port while the red probe is inserted into the port marked as v(ohm)mA unless measuring current for less than or equal to 10A.
• It should be noted that the multimeter is always kept in the off position when not in use.
How to Use a Digital Multimeter in Purposes:
Here are the details of where to use and how to Use a Digital Multimeter:
- It is usually the upper left corner of a digital multimeter (marked V, followed by a symbol of a straight horizontal line, and a segmented horizontal line under it) that is used to measure a DC voltage.
- The dial has to be set on the nearest maximum value (for example if we connect a 1.5 V cell, then we set the voltage to 20 V, i.e. the nearest maximum value is given in the digital multimeter).
- After connecting the probes to the ends of a battery or a cell, the reading gets displayed on the multimeter screen.
(It is interesting here to note that if the positive of the multimeter i.e. red is connected to the negative side of the battery/cell or the negative of the multimeter.
I.e. black is connected to the positive side of the battery/cell, then the reading will be a negative value)
Moving in the anti-clockwise direction, the segment measuring resistance, marked with an ohm symbol usually follows the DC voltage segment.
This is the most common Use a Digital Multimeter.
- A resistor of unknown resistance is taken and the dial pointer is set on the lowest marked value i.e. 200 ohms.
- Both the ends of the resistor are touched with the black and red probes.
- The resistance of the resistor is displayed on the multimeter screen.
- However, if the screen displays no reading, it means that the resistance must be of more than 200 ohms.
- In such a case, the dial has to be set on the next maximum value i.e. 2000 ohms for the reading to be displayed (the same process of increasing the maximum resistance value has to be repeated if there is still no reading).
It is important to note that the resistor should not be held in hands and should be kept on a stable platform to avoid any fluctuating values.
Next in the same anti-clockwork direction comes the segment for continuity test which is also used for checking a diode or an LED. It’s another important purpose to Use a Digital Multimeter.
- For testing a diode, attach the probes of the multimeter to the positive and the negative ends of the diode to be checked.
- After the reading is displayed, reverse the position of the probes on the diode ends.
- If this arrangement gives no reading that means that the diode is working perfectly, but if both the arrangements show readings, It is indicative of the diode not working properly.
(This comes from the fact that a diode lets current pass through only one of its side).
- In a continuity test, wires are tested for any breakage or damage in quite a similar way.
- After attaching the multimeter probes to both the ends of the wire, if reading is displayed along with a continuous beep sound then the wire is fine and if not, then the wire is damaged.
- Very similar to this, an LED can be checked. if it glows after attaching the positive and negative probes to its positive and negative ends then the LED is working!
The next function in line is the pulse generator. This is a very important purpose of Use a Digital Multimeter.
Frequency/Pulse/Square Wave Generator:
- This function is not very commonly used at hand.
- It generates frequency/ square wave/ pulse, from which signal output is also given and this can be tested with the help of an oscilloscope.
The HFE segment follows the pulse generator segment.
- HFE measures the current gain of the transistor.
- After moving the dial to this HFE segment, any transistor can be taken (NPN or PNP) and inserted into its respective slot which is separately given and marked on the multimeter.
- If a reading (which is the HFE) is displayed on the screen, it is indicative of the transistor being in the proper working state.
This function doesn’t work very effectively so if the reading is not displayed at once or if it is fluctuating.
The transistor should be moved a bit or reinserted by switching the side it initially faced, before concluding it to be damaged. Only can measure by Use a Digital Multimeter.
- The next segment marked as10 A in red is only a part of the further next segment mark as A and the whole of it is actually a single segment used to check how much ampere current is flowing through a circuit.
- The red,10 A function is only used to measure current whose nearest maximum is 10 A, and for this, the dial has to be pointing towards this function while the insertion point of the red probe in the multimeter has to be changed to the port marked as 10 A.
( If the current in this situation is measured with the red probe still being in the previous insertion port, then the multimeter will get damaged.
Even with the red probe in the changed new port, the current should not be measured for more than 10 seconds to avoid any damages to the multimeter)
- Now, with the dial pointer on 10 A, a circuit is taken.
- For measuring the voltage in the circuit the probes can be attached to the circuit in a parallel combination and this will immediately give the reading of the voltage.
- However, to check the current in the circuit, the probes of the multimeter have to be connected in series with the circuit and the reading is displayed!
- If the current is less, then the dial has to be moved from 10 A to the next shorter maximum value given i.e. 200 mA for a more accurate reading. It’s a great purpose to Use a Digital Multimeter.
The next and the last segment is that of an AC voltage measurement.
- This segment is marked by a ‘V’ followed by a horizontal-S symbol to denote AC voltage.
- An extension board connected to a current supply is taken and the dial pointer is set on 750 V as the voltage to be measured can be greater than 200V (the next value to 750V marked on the multimeter).
- The probes are inserted into the extension point and the reading of the voltage is displayed!
It should be kept in mind that a digital multimeter can never be 100% accurate and actual values can slightly deviate from the displayed readings.
And no matter how complex it seems, a proper understanding of all the functions of a digital multimeter, makes it easier to be used!