How to use an ohmmeter

Example:

Suppose we want to test a 100 ohm resistor with an ohmmeter. We choose a measurement scale from 0-200 ohms and connect the two terminals of the ohmmeter to the two terminals of the resistor. The ohmmeter will apply a known voltage to the resistor and measure the current flowing through the component. Using Ohm's law, the ohmmeter will then calculate the resistance of the component.

If the ohmmeter shows a reading of 100 ohms, it means that the resistance is in good condition and can be used in the circuit. If instead, the ohmmeter shows no reading or a very high reading, it means that the resistance is damaged and needs to be replaced.

In general, an ohmmeter is a very useful tool for testing electronic components before using them in a circuit. This helps to avoid future problems in the circuit and save time and money in troubleshooting.

How to use an ohmmeter

An ohmmeter is a tool used to measure the electrical resistance of an element. Its reading is expressed in ohms (Ω). This tool is very useful for checking whether an electronic component is working correctly or needs to be replaced.

Step 1: Preparation

Before using the ohmmeter, make sure it is turned off. Connect the tester cables to the appropriate sockets, usually identified as "COM" and "VΩmA". Also, check that the tester is set to measure resistance mode (symbolized by Ω).

Step 2: Measuring resistance

Now you are ready to start measuring the resistance. To do this, you need to connect the tester cables to the terminals of the element being tested. If you are testing a resistor, connect one cable to each terminal of the resistor. If you are testing another type of electronic component, read the manual to know which terminals to use.

Once the cables are connected to the component, turn on the ohmmeter and observe the reading on the display. If the reading is zero or close to zero, it means that the component has low resistance or is short-circuited. If instead, the reading is infinite or very high, it means that the component has high resistance or is interrupted.

Step 3: Interpretation of results

To correctly interpret the measurement results, you need to know the nominal value of the electronic component. For example, if you are testing a 100 ohm resistor and the ohmmeter indicates a reading of 95 ohms, it means that the resistor works well but has a slight variation from its nominal value. If instead, the reading was very different from its nominal value, for example 50 ohms, it means that the resistor does not work correctly and needs to be replaced.

Step 4: Turning off the ohmmeter

After finishing using the ohmmeter, make sure to turn it off to avoid draining batteries. Also remove cables from sockets to avoid accidental short circuits.

• In summary:

• Connect the tester cables to the appropriate sockets;
• Set the ohmmeter to resistance measurement mode (symbolized by the symbol Ω);
• Connect the tester cables to the terminals of the element being tested;
• Turn on the ohmmeter and observe the reading on the display;
• Interpret the results based on the nominal value of the electronic component;
• Turn off the ohmmeter and remove the cables from the sockets.

Common Mistakes to Avoid

Using an ohmmeter may seem simple, but there are some common mistakes that can compromise measurement accuracy. Here are some of the most common:

• Failing to calibrate the ohmmeter before use. Calibration is essential to ensure measurement accuracy. Before using an ohmmeter, make sure it has been properly calibrated.
• Selecting the wrong scale. The ohmmeter has different measurement scales, and choosing the wrong one can lead to inaccurate results. Make sure you select the right scale based on the resistance you need to measure.
• Failing to disconnect the circuit from its power source. If you're trying to measure the resistance of a component within a circuit that's still live, you'll get an incorrect reading. Always make sure you disconnect the circuit from its power source before taking measurements with an ohmmeter.
• Failing to check the ohmmeter probes. Ohmmeter probes can deteriorate or break over time, compromising measurement accuracy. Check them regularly to make sure they're in good condition, and replace them if necessary.
• Failing to read the display correctly. The ohmmeter display can show different types of readings, such as resistance in ohms or the selected scale value. Make sure you read the display correctly to avoid misinterpreting measurements.

Avoiding these common mistakes will help you get more accurate and reliable measurements with an ohmmeter.

Conclusion

The ohmmeter is an essential tool for anyone working with electronic circuits. Understanding the basics of using an ohmmeter will allow you to take accurate measurements and diagnose any problems in the circuit. Always remember to calibrate the ohmmeter before use, select the right scale, disconnect the circuit from its power source, check the probes regularly, and read the display correctly. By following these simple rules, you can use an ohmmeter effectively and get precise results.