A Fluke digital multimeter, or DMM, is used to take different types of electrical measurements, including voltage, amperage and ohms. It displays the readings digitally, giving greater accuracy than an analogue meter that displays measurements using a gauge and needle. Most types of digital multimeters have an array of advanced features, including displaying changes over time and monitoring setpoints in real time. While there are many different models of Fluke digital multimeters, they all share certain common functions.
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Things you need
- Safety glasses
- DMM test leads
Install the batteries according to the DMM instruction manual. Familiarise yourself with the symbols used on the rotary switch.
Familiarise yourself with the input terminals, usually located near the bottom of the meter. The terminals are colour-coded in red and black to match the test leads that came with your meter. To measure electrical current, use the amps or milliamps terminals for the red test lead. All other measurements use the volts terminal for the red test lead. The black terminal, or "COM," is the return terminal for all measurements.
Set the meter to measure resistance, continuity and conductance. The proper rotary switch setting is indicated by the "ohms" and "nS" symbols.
Insert the red test lead into the volts terminal on the meter. Place the red probe tip against the metal part of the milliamps terminal and then for the amps terminal. If the message "Leads Connected Incorrectly" appears, pull the probe tip out slightly until the meter displays either "OL" or a resistance reading. If the meter reads "OL" for either measurement, replace the appropriate fuse.
Set the meter to volts of alternating current, or AC, voltage using the "V" with the "~" setting on the rotary dial. Place the black lead in the "COM" terminal and the red lead in the volts terminal. Touch the red and black probe tips to the circuit you are measuring to read the AC voltage.
Set the meter to measure DC voltage using the "V" with the "---" symbol over it. Leave the leads in the terminals from the previous step. Touch the red probe tip to the positive or "+" terminal of a battery and the black probe tip to the negative or "-" terminal to read the battery's current voltage. You can also use this to check voltage at any particular point in a circuit.
Set the meter to measure resistance, continuity and conductance with the leads still in the same terminals. Touch the probe tips together, listen for a continuous beep. This beep indicates continuity. Use this mode to test for a good electrical connection between any two points in a circuit.
Tips and warnings
- Most Fluke digital multimeters will go into sleep mode to preserve battery power. The DMM will wake up when you press a button, turn the rotary switch or remove or insert a test lead.
- To test current, break the circuit and put the meter in series with the circuit. To test voltage, leave the circuit intact and place the leads in parallel with the circuit.
- Always check the fuses before beginning your measurements.
- Always wear safety glasses when working with electricity. De-energise the circuit whenever possible before taking any measurements.
- To avoid blowing a fuse when measuring current, take special note of any fuse ratings listed near the pairs of jacks, such as "10 A Max Fused" and "400 ma Fused" pairs. Make sure to switch the red test lead to a jack with a higher fuse rating than the circuit you are testing.
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