Multimeter Symbols
Every dial marking, button, display icon and jack, explained.
Compiled by DIY Repair Guide · reviewed 2026-09-14 ·how we research these
V~ is AC volts, V⎓ is DC volts, Ω is resistance in ohms, and the sound-wave icon is audible continuity. The display code OL indicates an open circuit or an input that exceeds the selected measurement range.
For step-by-step instructions on measuring wall outlets or batteries, see how to use a multimeter.
The Multimeter Symbol Chart
Find the symbol on your dial in the left column, then put the red lead in the jack listed beside it.
The black test lead always connects to the common (COM) jack. The red test lead connects to specific sockets according to the parameter you select on the dial.
| Symbol | What it measures | Red lead jack (typical) | Household example |
|---|---|---|---|
| V~ | Alternating current (AC) voltage (volts) | V/Ω jack. Black lead in COM | Wall outlet |
| V⎓ | Direct current (DC) voltage (volts) | V/Ω jack. Black lead in COM | AA or 9 V battery |
| mV | AC or DC millivolts | V/Ω jack. Black lead in COM | Low-voltage control circuit |
| Ω | Resistance in ohms | V/Ω jack. Black lead in COM | Electric heating element |
| Audible continuity icon | Continuity (sound wave or speaker icon) | V/Ω jack. Black lead in COM | Testing if a switch or cord conductor is intact |
| →| | Diode test | V/Ω jack. Black lead in COM | Testing a diode |
| F | Capacitance in farads | V/Ω jack. Black lead in COM | Heating, ventilation and air conditioning (HVAC) run capacitor (how to test one) |
| Hz | Frequency in hertz and duty cycle (%) | V/Ω jack. Black lead in COM | Generator output frequency |
| A~ / A⎓ | AC or DC current in amps | 10 A jack. Black lead in COM | Appliance operating current up to 10 A |
| mA and µA | Current in milliamps and microamps | mA/µA jack or VΩ jack depending on meter. Black lead in COM | Low-current electronics circuit |
| ° / °F / °C | Temperature in degrees | V/Ω jack. Black lead in COM | Thermocouple temperature reading |
| LoZ | Low input impedance (auto-voltage) | V/Ω jack. Black lead in COM | Preventing false readings from ghost voltage |
Alternating Current and Direct Current Symbols
A wavy line (∿ or ~) indicates alternating current (AC), while a solid horizontal bar resting over three dashed segments (⎓) indicates direct current (DC). Digital multimeters display these glyphs directly beside voltage and current markings on the selector dial.
On many meters, alternating and direct voltage share a single dial position. Pressing the select button toggles between the two modes, and the liquid crystal display (LCD) shows an AC or DC icon to confirm the active state. Fluke notes that AC millivolts appears as ∿ mV and DC millivolts as ⎓ mV on meter dials.
Direct current measurements also monitor circuit polarity. According to the Klein Tools MM400 instruction manual, if a minus sign (-) appears on the LCD, the test leads are being applied to the circuit in reverse polarity.
Resistance and Continuity Symbols
The Greek letter omega (Ω) represents electrical resistance in ohms. On many digital multimeters, resistance and audible continuity share a single position on the rotary selector dial.
Audible continuity uses a symbol that depicts radiating sound waves or a small speaker horn. When set to this position, the meter tests whether an electrical path is complete and sounds a beeper when the measured resistance drops below a predetermined limit.
Continuity beep thresholds vary by meter model. The Klein Tools MM400 sounds an audible signal below 50 Ω, while the manual-ranging Klein Tools MM300 requires resistance below 100 Ω. A technical guide from Fluke explains that the level of resistance needed to trigger the beeper varies by meter, but most indicate continuity with a measurement between 0 and 50 ohms.
Never measure resistance or continuity on a live circuit, as stated in the Klein Tools MM400 manual. For the exact testing sequence, consult our guide on how to check continuity with a multimeter.
What Overload and Open Circuit Indicate on the Display
The display code OL stands for overload or over limit, and it indicates that the measured value exceeds the input range of the multimeter. In resistance mode, OL appears when the leads are not touching anything or the resistor under test has failed.
According to Fluke, when test leads are separated in resistance mode, the display should show OL Ω because the meter starts measuring resistance before the leads touch anything. When the probe tips touch each other directly, the display ideally reads 0 Ω.
In continuity mode, the display shows OL when the circuit is open, such as a broken wire or a switch turned off. During a diode test, the Klein Tools MM400 manual notes that OL indicates reverse bias on a functioning diode, while an open diode displays OL in both test directions.
Multimeter Buttons and Display Indicators
Each button changes what the display shows, and each icon tells you which mode or warning is active.
Replace the batteries as soon as the low battery icon appears, because the Klein Tools MM400 manual warns that low batteries can cause false readings that lead to electrical shock.
| Marking | Type | Function and operating behavior |
|---|---|---|
| HOLD / H | Button & icon | Captures and holds a stable measurement on the screen. Press again to release |
| AutoHOLD | Button & icon | Captures a measurement, beeps, and locks the measurement on the display |
| MIN MAX | Button & icon | Stores input values. Beeps when a value is breached. First press shows max, second shows min |
| RANGE | Button & icon | Switches to manual mode and cycles ranges. Holding over one to two seconds restores auto-ranging |
| REL / Δ | Button & icon | Relative mode: stores existing reading as a delta offset and resets display to zero |
| SEL / Yellow button | Button | Toggles secondary functions marked in yellow or orange, such as AC/DC or °F/°C |
| Audible signal button | Button | Activates the audible continuity beeper when paired with resistance mode |
| Low battery icon | Display icon | Signals low battery power. Replace batteries to prevent false readings and shock hazards |
| Auto power off icon | Display icon | Shows that auto power off is active |
| M, k, m, μ, n | Display prefix | Metric multipliers: mega (×10⁶), kilo (×10³), milli (×10⁻³), micro (×10⁻⁶), nano (×10⁻⁹) |
Multimeter Jack Markings
The common (COM) jack takes the black test lead for all measurements. Fluke's rule is that the jack you choose for the red lead must match the setting on the dial.
A Fluke digital multimeter has four jacks: COM, V/Ω (voltage, resistance, capacitance, temperature, diode), A (up to 10 A), and mA/μA (0 μA to 400 mA). In contrast, the auto-ranging Klein Tools MM400 has only three jacks: COM, 10A, and VΩ. On that meter, currents below 400 mA share the VΩ jack, while currents over 400 mA up to 10 A use the 10A jack. Current jacks differ per meter, so follow your meter manual to select the correct terminal.
The measurement category (CAT) marking appears near the input jacks. The Klein Tools MM400 carries a CAT III 600V rating, indicating suitability for test circuits connected to the distribution part of a building's low-voltage mains installation. Fluke lists the four measurement categories:
Never use a meter on a circuit with voltages that exceed its category rating, and connect only with CAT III or CAT IV rated test leads. Use caution above 25 V AC root mean square (RMS) or 60 V DC, as those voltages present an electrical shock hazard.
- CAT I: Protected electronic equipment.
- CAT II: Single-phase receptacle-connected loads such as appliances and portable tools.
- CAT III: 3-phase distribution including single-phase commercial lighting and equipment in fixed locations such as switchgear and polyphase motors.
- CAT IV: 3-phase at the utility connection, outdoor conductors, electricity meters, and service entrances.
On the Klein Tools MM400, both jacks that measure current are fused. The Klein Tools MM400 prints fuse ratings below the fuse symbol, specifying a 500mA/600V fast-blow fuse on the VΩ jack and a 10A/600V fast-blow fuse on the 10A jack. Exceeding 500 mA on the VΩ jack or 10 A on the 10A jack can blow the fuse. The manual-ranging Klein Tools MM300 uses a 200mA/600V fuse on its VΩ jack. To check a meter's own fuse, see our walkthrough on how to test a fuse with a multimeter.
Common questions
Which is AC and DC on a multimeter?
The wavy line (V~ or ∿) represents alternating current, which powers household wall outlets. The solid line over a dashed line (V⎓) represents direct current, which powers battery-operated electronics.
Which symbol on a multimeter represents resistance?
The Greek letter omega (Ω) represents resistance measured in ohms. It shares a dial position with audible continuity on many digital multimeters.
How do I read my multimeter?
Identify the dial setting to confirm the measurement type, place the red lead in the matching jack, and insert the black lead into COM. Read the numerical value on the screen along with any metric prefix such as k for kilo or m for milli. If the screen displays OL, the measurement is either an open circuit or exceeds the active range.
How does a beginner use a multimeter?
Connect the black lead to COM and the red lead to the V/Ω terminal for basic tests. Select either DC voltage for batteries or AC voltage for receptacles before placing the probe tips on the circuit. Step-by-step instructions for basic measurements are detailed in our guide on how to use a multimeter.
What is the continuity symbol on a multimeter?
The continuity symbol looks like radiating sound waves or a small speaker. On many meters it shares the resistance (Ω) dial position, and a select or audible signal button turns the beeper on.
What does OL mean on a multimeter?
OL indicates overload or over limit on a digital multimeter. When checking resistance or continuity, OL means the path between the probes is open, such as a broken wire.