Understanding the Multimeter Controls

  • Dial: Selects the measurement function and range (or AUTO for auto-ranging models)
  • COM jack: Black probe always goes here (common/negative/ground)
  • VmAΩ jack: Red probe here for voltage, resistance and small current
  • 10A jack: Red probe here only when measuring high current (10+ amps)
  • Display: Shows the measured value and unit

The Most Useful Tests

1. Continuity Test (Check if a Circuit is Complete)

  1. 1

    Set to the continuity symbol

    The continuity symbol looks like a soundwave or diode symbol, often combined with a beeper icon. Set the dial here. The multimeter beeps when the probes touch each other — confirming the continuity function is active.

  2. 2

    Touch probes to each end of the component or wire

    Power off the circuit first. Touch one probe to each end of what you are testing (a fuse, a wire, a switch). If the circuit is complete (conducts electricity), the multimeter beeps. No beep = open circuit (broken wire, blown fuse, open switch). Excellent for testing fuses, extension cords, switches and detecting broken wires.

2. DC Voltage Test (Check Battery or 12V Circuit)

  1. 3

    Set to DC Voltage (V with straight lines)

    For batteries and car electrical: set dial to DC Voltage (V— or VDC). Choose a range above the expected voltage (20V for a 12V car battery). Touch red probe to positive (+) and black probe to negative (-). A fully charged 12V car battery reads 12.6V at rest.

3. AC Voltage Test (Check Mains Power — Use Carefully)

Set to AC Voltage (V~ or VAC). Range above 250V for Australian mains (240V). Insert probes into an outlet (or use a plug adaptor — never insert bare probes directly into a power point). Reads approximately 240V if power is present. Be extremely careful with mains voltage — only do this if you are confident and the multimeter is rated for the voltage.

4. Resistance Test (Ω)

Set to Ω (ohms). Power off the component. Touch probes to the component. Reads resistance in ohms, kΩ (kilohms) or MΩ (megohms). An open circuit reads OL (overload/infinity). Useful for testing resistors, checking if a heating element is functional, or measuring coil resistance.

Safety rulesNever exceed the multimeter’s rated voltage. Always check probe condition — cracked or exposed wire in probes is dangerous. When testing mains voltage, work with one hand where possible (reduces risk if accidental contact occurs). Keep the multimeter set to the correct function before connecting — a resistance test connected to a live circuit destroys most multimeters.

Frequently Asked Questions

For home DIY use, a mid-range auto-ranging digital multimeter from a reputable brand is ideal. Recommendations: Fluke 101 (~$80, very accurate, durable, trusted brand), UNI-T UT61E+ (~$50, excellent value for money), or a Klein Tools MM400 (~$60). Avoid very cheap ($5–15) multimeters — they can have inaccurate readings and substandard safety ratings. The Fluke 101 is arguably the best entry-level choice for reliability and longevity.
OL stands for Overload or Out of Limit — the reading exceeds the selected range, or the measurement is infinity (open circuit). In continuity mode: OL means no connection (open circuit). In resistance mode: OL means infinite resistance (no conduction). In voltage mode: OL means the voltage exceeds the selected range — switch to a higher range. OL is not an error message; it is a valid reading indicating an out-of-range or open circuit condition.