22/02/2025
MULTI METER (Ohm Meter)
An ohmmeter is a useful tool for checking electronic components by measuring their resistance. Here’s how you can use it for different components:
1. Resistors
• Set the ohmmeter to the appropriate resistance range.
• Connect the probes to both ends of the resistor.
• Compare the measured value with the resistor’s labeled value (color code or printed).
• A significant difference may indicate a damaged resistor.
2. Capacitors (Basic Check Only)
• Discharge the capacitor completely before testing.
• Set the ohmmeter to a high resistance range.
• Connect the probes to the capacitor terminals.
• A good capacitor will show an initial low resistance that increases as it charges. A constant low reading may indicate a shorted capacitor, while an infinite reading may indicate an open capacitor.
3. Diodes
• Set the ohmmeter to the diode or low-resistance setting.
• Connect the positive probe to the anode and the negative to the cathode.
• A good diode will show low resistance in one direction and high (or infinite) resistance in the reverse. If it conducts in both directions, it is faulty.
4. Transistors (Basic Check Using Diode Test Mode)
• Identify the base, collector, and emitter pins.
• Measure resistance between base-emitter and base-collector like you would with a diode.
• A good NPN transistor should conduct (low resistance) from base to emitter/collector but not in reverse.
• A PNP transistor should conduct from emitter/collector to base.
• If both directions conduct or show infinite resistance, the transistor is faulty.
5. Coils and Inductors
• Set the ohmmeter to a low resistance range.
• Measure across the coil terminals; a low resistance indicates a good coil, while an open circuit means it is damaged.
6. Switches and Fuses
• Set the ohmmeter to a low resistance range.
• For a fuse, a good one should show near zero resistance. An open circuit means it is blown.
• A switch should show zero resistance when “on” and infinite resistance when “off.”
Safety Tips
• Always power off and discharge components before testing.
• Avoid measuring resistance in-circuit as other components may affect readings.
• Use the correct range setting to avoid inaccurate results.
