Digital multimeters have come a long way since their analogue counterparts. Needle indication meters, which are analogue, typically have only two functions--reading voltage and resistance. Today's meters can read a host of various electronic components. These functions are also built into the digital meters and can be accessed by a single selector switch. Accuracy is another advantage of a digital meter. Checking electronic circuits for its resistance can now show slight variations in a circuit. The resolution of the modern multimeter is typically +/- 0.01 ohm. Combining precision electronics with a high-resolution screen also accounts for high accuracy. Older analogue meters depend on needle placement and the vision of the operator.
- Skill level:
- Moderately Challenging
Things you need
- Digital multimeter (see resources)
- Specifications of electronic equipment
Turn the multimeter to the "ohms" position on the selector. Insert the leads into the proper connectors. Place the red lead into the "ohms" opening, and the black lead into the "common" opening.
Touch the two leads together. Record the resistance of the leads to the meter with pencil and paper. In this particular instance, the meter may read 1.3 ohms. This is called calibrating the meter reading. The calibrated reading may change due to different environmental conditions such as temperature and moisture.
Check the circuit you want to verify for a particular piece of electronic equipment. For example, it may be a magnetic coil with a resistance of 18.6 ohms as indicated in the specifications. Remove all electrical power from the device.
Use a screwdriver and remove any wires from the terminals that supply power to the coil. Wires that are still connected can lead to a false reading. Touch both leads to the separate terminals of the coil. In other words, the red lead to one screw terminal and the black lead to the other screw terminal. You need to form a closed electrical circuit with the meter.
Read the meter. The digital indicator displays 19.9 ohms. Subtract the calibrated resistance reading of 1.3 ohms from the display of 19.9 ohms. The final resistance of the coil is the specified 18.6 ohms.
Tips and warnings
- Other non-critical resistance readings may not require a calibrated reading.
- Some meters will have the calibrated function built into the operation of the digital meter.
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