A fluke multimeter, also known as a digital multimeter or DMM, is an electrical device used for troubleshooting electrical or electronic equipment. It measures
It also helps in checking
- Continuity of wires & fuses
- Power cables
The best fluke multimeter comes with a higher accuracy and very less probability of error. Some DMMs have a special feature for measuring AC RMS value. Their price ranges above $100. Some also lock the ports with respect to the knob settings, in order to prevent mistake on part of the user.
PART 1: MEASURING VOLTAGE
You can use a DMM for measuring AC and DC voltages. DC voltage is the one provided by the batteries whereas AC voltage is available in the power sockets we have at our homes.
Take the two leads, red and black, and insert them first into the fluke multimeter and attach their other ends to the battery terminals.
- Insert the black probe into the COM port and connect its other end to the battery’s ground or “- ”.
- Insert the red probe into the VΩ port and connect its other end to battery’s power or “+”.
- Turn the dial to the DC voltage setting, for a battery. If your meter doesn’t have an automatic range selection feature, choose a range manually. For a 1.5 V battery, set the meter dial to 2V and likewise. Don’t select too small or big a range as it will lead to error in the value on display.
- Now, if the battery is new, you will get a reading of 1.5V on the multimeter display. Similarly, if you switch the two leads across the battery terminals – red in place of red and red in place of black – you will get a reading of -1.5V on display.
- If you are not getting the required voltage on output, like in place of 12V you are getting a lower or higher voltage, it indicates that there is some fault in the circuit connections.
- If you want to measure the voltage at any point in a circuit, plug the probes in the meter as told before. Connect their other ends to the wires across which you want to know the voltage- red lead to the live wire in the circuit and black lead to the circuit’s ground.
- A conventional method to measure voltage is in parallel to the load. Thus, you also have to connect the multimeter in parallel to the load, whose voltage you want to determine.
PART 2: MEASURING CURRENT
- Current is always measured in series of the circuit element. Therefore, you have to insert a multimeter in series with the load.
- Plug the black/ground probe into the COM socket & the red/positive probe into the mA port (if the current is low) or 10A port (if the current is high). If the current is greater than mA and you have inserted the probe into mA port, the multimeter fuse will blow up.
- Switch the dial on the meter to the correct current range (A for 10A port and mA for mA port). You can always change the range to achieve an accurate reading.
For measuring current and voltages, ensure that the probes are in correct sockets – A socket for current and V socket for voltage. Otherwise, the wrong connections for measuring current or voltage will blow up the meter.
PART 3: MEASURING RESISTANCE
- Make the connections of the DMM leads as shown in the image below. Notice that the connection is same as that for measuring voltage.
- Switch off the power supply to the circuit.
- Disconnect the resistance you want to measure from the circuit.
- Set the dial to the lowest ohm range i.e. 200Ω or the like.
- Place the tip of each lead on each end of the resistance. If you get an “I” on the display, it means that your selected range is lesser than the resistance you are measuring. Turn the dial to a higher value and keep on doing it until you get a numerical value on the display.
PART 4: CHECKING CONTINUITY & FUSES
One more use the DMM offers is to check for continuity or breaks in the circuit.
- Once again, the connecting leads go in the same port as that for voltage measurement.
- Set the dial on the continuity range. In the image of the symbols at the start of this blog, see which symbol represents the continuity range (one which appears as a series of arcs of a circle)
- Now, turn off the power supply to the circuit because you have to test a conductor.
- Place the two leads across each terminal of the conductor or fuse.
- The meter will give a beep or buzz for a resistance of less than 30 Ω. The resistance value also appears on the display. If, however, there is a break in the continuity, the display will show the digit "1", which means overload condition.
- In the same way, you can also detect a good diode from a faulty one.
The RMS value of an AC voltage, also known as the effective value, is Vpeak / √2. The best fluke multimeter measures this RMS value with highest degree of accuracy for all waveform shapes. I hope you found this article useful for troubleshooting your next DIY electronics project. All you have to keep in mind is the correct connection of the leads for measuring a certain electrical quantity; rest of the work is quite simple. Share this blog in you circle and other social networks and don’t forget to leave your comments and queries regarding the fluke multimeter.
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