Multimeter Symbols: MM420, Fluke 107, 115 and 117 Reference

V~ means AC voltage, V⎓ means DC voltage, Ω means resistance, and the sound-wave icon means continuity. For a first meter with temperature and small-current functions, our pick here is the Klein MM420; the Fluke 107 is the pocket choice and the 117 adds AutoVolt and VoltAlert. Find your exact model below before interpreting a shared switch position: the buttons and defaults differ.

Find your model and symbol

These are symbol reference maps, not connection instructions. For low-voltage procedures, use how to use a multimeter alongside your manual. Leave exposed mains and panel work to a licensed electrician.

Read the dial, active LCD function and terminal label together. The dial names the available measurement; the display identifies the selected mode and units; the red-lead terminal must match that function. Fluke's symbol explainer explicitly warns that its composite dial combines several meters' functions.

1. 1

   Dial

   Find the function, including any secondary marking at that position.

2. 2

   Display

   Confirm the active function, AC/DC indicator and unit prefix.

3. 3

   Terminal

   Match the red-lead input to the selected measurement in the exact model's manual.

Common dial symbols, translated

Shapes below are text approximations. Use the linked model manuals to match the printed artwork.

Source: Fluke's symbol key and Klein's LCD and meter legends, printed page 6.

Compare the functions behind the symbols

Sources: MM420 manual, 107 manual, 115/117 model-specific tables and Fluke's 107 specification/Q&A. “Not listed” refers to these models' function lists, not operating-temperature specifications or optional accessories.

Klein MM420: temperature and small-current pick

The MM420's white markings are defaults; orange markings are secondary functions selected with SEL. Its manual, printed pages 8–14, gives this map:

The easy mistake is assuming Ω is active because it shares the beeper position. Check the LCD icon. H means data hold, AC/DC identifies the active electrical mode, and MAX/MIN identifies a stored maximum or minimum. Lead Alert LEDs indicate the appropriate jacks; they do not replace checking the function and terminal labels.

Temperature is a reason to choose this model, but the supplied thermocouple is suitable only below 356°F / 180°C, despite the meter's wider temperature specification. See Klein's temperature instructions.

Check price on Amazon

Fluke 107: pocket pick

The 107 has separate AC and DC voltage positions. Its 106/107 manual, printed pages 12–19, identifies the 107-only functions:

This reverses the MM420's resistance/continuity default: the 107 starts at resistance. HOLD freezes the reading; the LCD's AUTO indicator means automatic ranging. Do not borrow the 115/117 RANGE-button instructions for this control layout. The 107 product page confirms it is not True RMS.

Check price on Amazon

Fluke 115: standard service reference

The 115 is the reference for the shared service functions below; the 117 adds the positions in the next section. Use the 115 product page and shared manual's feature table and illustrations.

LoZ on a 115 does not mean AutoVolt. The manual documents a low-impedance capacitance option, identified by LCAP at startup, for both 115 and 117. Its accuracy and dynamic range are reduced. Auto-V/LoZ voltage selection belongs to the 117 here.

Also check the version: Fluke lists FLUKE-115 and FLUKE-115 CAL; CAL adds a traceable calibration certificate with data. The 115/117 product-page comparison widgets show a temperature row, but their model-specific manual lists no temperature function. We use that function table rather than treating the widget as proof of a temperature mode.

Fluke 117: AutoVolt and VoltAlert pick

The 117 manual adds these functions to the shared map:

Auto Volts and Auto are different: Auto Volts means automatic AC/DC voltage selection; Auto means automatic range selection. The 117 product page identifies its low-impedance voltage mode as a way to prevent ghost-voltage readings.

VoltAlert has sensitivity indications Hi / Lo, not measured voltage values. Fluke warns that voltage can still be present without a detection indication and that shielded wire can defeat detection. The 117/323 combo kit is a package containing the 117 plus a separate clamp meter, rather than another 117 dial layout.

Check price on Amazon

Read unit prefixes before the number

The MM420 LCD legend includes M, k, m, µ and n. Prefixes scale the unit; case matters. Using NIST's SI prefix table:

The prefix changes magnitude, not the measurement type: mV is voltage; mA is current. A unit shown in a shared display drawing does not establish a usable range on every model.

COM and current jacks: the model exception

COM means common/return. The other input labels need the exact manual:

Sources: Klein, printed pages 10–11, 107 terminal table and 115/117 terminal table. A generic diagram showing a separate mA socket would mislead an MM420 owner.

OL, HOLD and other display indicators

Sources: MM420 LCD legend and instructions, 107 display and HOLD warnings, and 115/117 display tables.

How we choose

This is manufacturer-document research, with no physical testing claimed. We compared dial illustrations, button descriptions, terminal tables and model-specific function lists, including the shared-manual exceptions. Source snapshots support the reference; our broader method is at How we choose.

Buying advice: replace a missing function, not an unfamiliar symbol

The 115/117 have amp ranges without dedicated µA/mA positions; the MM420 supplies those functions. The 115 has low-impedance capacitance but lacks the 117's AutoVolt position. Temperature is listed for the MM420, rather than the other reference models.

• Yes: MM420: dedicated µA/mA functions and temperature
• Partly: Fluke 115: LoZ capacitance, without AutoVolt voltage selection
• Yes: Fluke 117: AutoVolt/LoZ voltage and VoltAlert

Choose an upgrade only when its documented function fills your gap. For the broader shortlist, see best multimeters; for operating procedures, return to how to use a multimeter.

Verdict

Start with the exact model map, then read the LCD mode and unit prefix. Choose MM420 for temperature and small-current ranges, 107 for the pocket format, or 117 for AutoVolt and VoltAlert. The 115 is the standard service reference, with its own important LoZ-capacitance exception.