Check how the voltage, current, resistance can be measured, check if the transistors work, check the continuity and all!
What is a Digital Multimeter and What Does it Measure?
A digital multimeter is an essential tool for testing, diagnosing and troubleshooting electrical circuits, components and devices. The first digital multimeter was introduced in the late 1970s and has proven to be much more accurate and reliable than older needle-based analog meters.
It is primarily used to measure voltage (volts), current (amps) and resistance (ohms). But this is just the beginning of what this amazingly effective tool can do. Below are the common uses of your digital multimeter.
Note that the instructions are given here apply to most multimeters. However, the accurate method and how the screen can be read may vary slightly depending on the features and functions of your particular device.
A Digital Multimeter is a test tool used to measure two or more electrical values—principally voltage (volts), current (amps) and resistance (ohms). It is a standard diagnostic tool for technicians in the electrical/electronic industries.
Before jumping into how To Use a Digital Multimeter, read Fluke’s promotional articles on multimeters as well. They will give you strong feedback on what a multimeter is and what it can do as well and keep reading to get some tips from our favourite electricians.
How To Use a Digital Multimeter
How to Measure Voltage with Digital Multimeter
There are usually two separate voltages that can be measured by a multimeter. One is DC voltage and the other is AC voltage.
All electronics devices operate at DC voltage (conventional AC will be converted to DC) and hence DC voltage is the most measurable parameter. The multimeter can measure both AC and DC voltages. Let’s start with DC voltage.
How to Measure DC Voltage with Digital Multimeter
Two things need to be tested on a multimeter before proceeding with any measurement. These are the position of the test lead (a.k.a test probe) and the mode/range selection.
By default, the black test lead position should be in the COM slot and the red test lead should be in the V slot. This position will only change if we measure the current.
So, the black test lead should be in the COM slot and the red lead in the V slot to measure a voltage. Oh, the black test lead should be in the COM slot and the red lead in the V slot to measure a voltage.
Now we need to select the mode using a knot-like controller in the centre of the multimeter. We should look for the DC voltage symbol and select a range below it.
By default, the range will be like 200MV, 2V, 20V, 200V and 600V. You can select the range based on the voltage level you are planning to measure. And don’t worry if you choose a lower range you can always hit and try but it doesn’t explode.
For example, if you measure 35V and if you keep it in the 20V range, you can read the meter 1, which means you should choose a higher voltage range for 200V in this case.
I have placed the meter on reading the DC voltage within the 20V range. After setting the meter, we can only place the probes on the terminal on which we have to measure the voltage.
. Place the red lead on the positive terminal and Black lead to the negative terminal and you will get the value of voltage. If you get the value opposite the pole of the cable, it will be accompanied by a negative sign, always use searches on the correct pole to avoid errors.
When debugging applications, you can measure any battery, DC adapter, phone charger and even voltage across each component of a circuit.
How to Measure AC Voltage with Digital Multimeter
AC voltage is rarely measured using a digital multimeter but it is still important where AC mains are involved. Place the red lead in the V slot and the black lead in the COM slot to measure the AC voltage.
Now set the mode using the knock, we need to put it in the AC voltage symbol. Normally we will have two ranges for AC voltage, and they are 200V and 600V.
For measuring AC voltage in India which is 220V, we have to put it in 600V mode. The measurement process is similar to measuring DC voltage, but we don’t have any variations here because of working with AC.
How to Check Continuity with Digital Multimeter
Another important and useful feature of a multimeter is to test the continuity. This is a lifesaver tool that helps debug electronics, whether it’s your new PCB or a simple breadboard connection you can use the continuity tool to check if there is any connection between the two terminals.
It can also be used to detect broken wires. Check for continuity of any wire or circuit, place the black probe in COM slot and red probe in V slot, then remove knot as continuity symbol. To test the continuity between Terminal A and Terminal B, place one probe (any probe) in Terminal A and the other in Terminal B.
If there is a connection between Terminal A and Terminal B, the meter will read zero and you will get a “beep” sound. You will not receive a beep without a connection.
How to Measure Resistance with Digital Multimeter
The most commonly used and essential component of electronics is resistors. There are different types of registers available based on their power rating and resistance value; colour codes will specify the value of each resistor.
It is important to learn how to read the value of a resistor using colour code but there can be some problems that are very difficult to read the colour. In this case, we can easily use a multimeter to read the resistance value of the resistor.
To measure resistance with a multimeter, make sure that the black probe is in the COM slot and the red probe is in the V slot. Now, turn the knob to the resistance symbol.
Again we have a range of 200Ω to 2MΩ, choose whatever you want, putting it at 20k quality. You can always try different ranges to get the right range suitable for your resistor.
A new battery will produce slightly more than its rated voltage (for this battery, 1.5 volts). Note that this meter has two different settings: Use the voltage mode of your meter to test the battery output, starting with the simplest, most basic test for one volt, the alternating current, and the other for the direct current of the volt.
First, plug the black probe of the meter into the marked jack – COM (common). Insert the red probe labelled Volt or + V into the jack (next to the V, you’ll also see a symbol that looks like an inverted horse, we’ll get to it in a minute).
Most modern meters color-coding the jacks make this setup all but silly. The black general investigation goes into Black Jack; The red probe goes to Red Jack.
Now switch (dial) the volt DC; Because batteries supply direct current (DC), not current alternatives (AC). Hold the red probe tip against the battery’s positive (+) external-shaped terminal and hold the black probe against the ward negative (-) inner-shaped terminal.
The battery voltage will fall on the meter display screen. For example, a fully charged AA battery must read at least 1.5 volts. And you can use your digital multimeter to test virtually any battery, from AAAS to car batteries.
Note that the technique described above only tests the voltage, not the ability of the battery to supply current under load. The test gives you a rough idea of whether the battery is good, shot, or needs to be charged.
Testing Electrical Outlets
Here’s how to determine if your home wall outlets are supplying the right voltage, which is 120 volts in most modern homes. Plug the black probe into the meter’s black COM jack and the red probe into the red volts jack.
Then turn on the rotary switch on the volt AC (VAC), which is also indicated by a wavy wave line on the dial. Press the tip of the red probe into the short (hot) of the two vertical slots of the outlet.
Place the black probe in the long slot (neutral). Check the readout on the meter screen. A properly functioning outlet should produce 110 to 120 volts.
Next, remove the black probe from the outlet – leaving the red probe – insert the black probe into the small, round hole (ground) at the bottom of the two slots. The reading must remain the same. If this is not the case, the outlet is incorrectly wired or the ground is probably missing; An electronic call.
Testing a Wall Switch
Got a faulty ceiling light? Here’s how to determine if a problem has a switch. First, turn off the power to the switch, remove the cover plate and unscrew the switch from the wire. Before disconnecting the wires, label them or take a photo with your phone so you can connect them properly.
Loosen the switch terminal screws, unhook the wires from the wires and remove the switch. Rotate the meter dial in ohm setting. Set the resistance limit at X1. If your meter has auto-range, you can tell the auto-ranging meter when you turn on the dial in the Vault AC (VAC) setting, the word “auto” appears on the screen) skip this step.
Plug the black inquiry into the COM jack and the red probe into the red V jack. To test a single-pole switch (the simplest type; it has two brass screws and a green screw). Flip the switch to the off position.
Now touch the probe of the meter with the brass screw terminal next to the switch – it does not matter which screw will touch which screw.
As soon as the switch is turned off it would be best if you got a text of the OL (you can also get other readings, such as 99999 or a symbol like this or also: L). It means overload or over-limit; The resistance is so high that it cannot be measured.
At first, this may not seem understandable (you think the meter will read zero ohms), but the meter tells you that when no internal contacts touch the inside of the switch, the resistance across the open contacts is so large that the meter cannot read it. Now flip the switch on and the meter should read less than one ohm.
If this is not the case, the switch should be defective and replaced. Another simple test is to rotate the meter dial in the position for continuity. It means uninterrupted electrical path.
The symbol for continuity on the face of the meter is an altar shape that indicates that the sound extends from point to point. Attach the meter across the switch connections and flip the switch up and down.
The switch is good if the meter beeps with the switch with the on position. If the meter turns the switch on, the switch is bad without beeping the meter.
Testing Extension Cords
Sometimes it’s smart to use your meter to check old extension cords because damaged cords can push you or start a fire. Start by plugging the extension cord from the wall and turning the meter dial into an ohm setting.
To examine the ground of the cord, press the red probe into the small hole in the female end of the cord. Then touch the longest round (ground) probe extending from the male edge. The resistance of an uninterrupted circuit measured from these two ends will be 8 ohms or less.
Now touch the red probe at each flat prompt on the male end to make sure the OL read. In this fashion the cord must have an open circuit when analyzed; There should be no contact between the ground pin and the connecting wire to any of the other two wires inside the cord.
Next, insert the red probe into the short (hot) slot on the female end of the cord. Touch the black probe from the narrow flat edge to the male end. The electrical continuity through the cord will have a resistance of .8 ohms or less.
Then touch the black probe until the wide plane vibrates and then the round fork, the meter should show no continuity and an O.L. show to read these two terms.
Finally, take the red probe and press it into the longer (neutral) slot on the female end of the cord. Look at the black probe and touch the pendant of the spacious flat. Continuity will have a resistance of .8 ohms or less.
Touch the short prong and then the round prong black probe for an O.L. Continue reading. After making sure that the cord has no shorts, run a voltage test.
Plug the cord into the electrical outlet and turn the meter dial on the volt AC. Insert the black probe into the round hole on the female end of the cord and press the red probe into the narrow slot. You should have a reading around 120 volts.
Now move the red probe to the long (neutral) slot to make sure you read about. 1 millivolt (there is a negligible voltage between the ground and neutral of the outlet and the ground and neutral of the cord).
Leave the red probe in the long slot and move the black probe in the short slot to read a voltage of about 120 volts, ensuring that the extension cord is in good condition.
In addition to all its wonderful electro-testing capabilities, most modern digital multimeters can also take temperature readings. In temperature, mode rotates the meter dial, then press the select button to toggle between Fahrenheit and Celsius.
Plug the thermocouple into the meter to read the air temperature, or insert the temperature probe to take temperature readings of liquids, gels or to track the surface temperature of the gas dryer. You can observe the temperature cycle of the device without touching it with your hands.
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