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Tools & Workshop Comparisons · Reviewed September 26, 2026

Fluke 117 vs Klein MM420 Digital Multimeter

Both are True-RMS, CAT III 600V meters that measure up to 600V and 10A. Fluke adds VoltAlert, AutoVolt and low-impedance mode; Klein adds temperature, duty cycle, a thermocouple and lead-placement alerts.

Best for

Trained users comparing exact electrical meter functions, safety categories and ranges for building maintenance, controlled jobsite or workshop tasks.

Probably not for

Untrained live electrical work, measurements above a meter or lead rating, use with damaged probes or fuses, or choosing solely from the highest voltage number.

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Fluke 117 Electrician's Multimeter

Fluke specifies the 117 as a 6000-count, True-RMS digital multimeter rated CAT III 600V. It measures up to 600V AC/DC and 10A AC/DC, plus resistance to 40 megohms, continuity, frequency, capacitance and Min/Max/Average. VoltAlert provides integrated non-contact voltage detection, AutoVolt selects AC or DC voltage and a selectable low-impedance mode helps reject ghost voltage. A backlight, leads and holster are included.

Pros

  • VoltAlert, AutoVolt and low-impedance mode address common electrician workflows without a second detector.
  • The 6000-count display provides finer nominal count resolution than the MM420 4000-count display.

Cons

  • It does not provide the MM420 temperature, duty-cycle or included thermocouple functions.
  • Its integrated detector is an initial indication, not a substitute for a proper contact test when proving a circuit de-energized.

Who it’s for: Choose it for non-contact voltage detection, AutoVolt and ghost-voltage rejection within CAT III 600V work. Skip it when temperature measurement or a lead-placement alert is more useful.

Check Fluke 117 Electrician's Multimeter on Amazon

Klein Tools MM420

Klein rates the auto-ranging MM420 CAT III 600V and specifies True-RMS measurement. It measures up to 600V AC/DC, 10A AC/DC and 50 megohms, plus capacitance, frequency, duty cycle, diode and continuity. Its included thermocouple covers temperatures from -40 to 1832 degrees Fahrenheit. The 4000-count meter includes Lead Alert illumination for lead placement, a backlight and a 6.6-foot drop rating.

Pros

  • Temperature, duty-cycle and the included thermocouple add measurements the Fluke 117 does not provide.
  • Lead Alert illuminates the appropriate input-jack placement, and the 50-megohm resistance ceiling exceeds Fluke's 40-megohm figure.

Cons

  • It lacks the Fluke 117 integrated non-contact voltage detector, AutoVolt selector and low-impedance mode.
  • Its 4000-count display has a lower nominal count than the Fluke 6000-count display, though accuracy depends on each range specification.

Who it’s for: Choose it for temperature, duty-cycle and lead-placement guidance within CAT III 600V work. Skip it when non-contact detection or low-impedance voltage measurement is central.

Check Klein Tools MM420 on Amazon

The matching CAT III 600V rating keeps the comparison like for like

Fluke and Klein both rate these exact meters CAT III 600V. Measurement category describes the transient-energy environment a meter is designed to withstand at its marked voltage. A matching category still does not make every 600V measurement appropriate or remove the need to understand the circuit and procedure.

The meter, leads, probes, fuses and accessories must all be intact and rated for the location. De-energize when the procedure permits, verify the meter on a known source before and after a test, and use proper personal protective equipment and training. Building service and live-panel work should be left to qualified professionals.

Fluke emphasizes voltage identification and ghost-voltage control

The 117 integrates VoltAlert non-contact voltage detection for an initial go or no-go indication. AutoVolt chooses AC or DC voltage, and the low-impedance setting reduces false readings caused by capacitive coupling. These are workflow features for electricians, but a non-contact indication never replaces a properly performed contact test when proving a circuit de-energized.

Fluke uses a 6000-count display, while Klein lists 4000 counts. Display count affects how finely a range can be divided, yet accuracy is specified separately by function, range and conditions. Do not infer that one count figure makes every reading more accurate. Klein's Lead Alert instead focuses on illuminating the appropriate input-jack placement.

Klein adds temperature and duty cycle

The MM420 includes a thermocouple and publishes a temperature range from -40 to 1832 degrees Fahrenheit, plus duty cycle. Fluke instead emphasizes non-contact detection, automatic voltage-type selection and low-impedance voltage measurement. The better set depends on whether the real work is HVAC-style temperature checks or building-voltage troubleshooting.

Both meters handle up to 600V AC/DC and 10A AC/DC, plus capacitance, frequency, continuity and diode checks. Klein publishes resistance to 50 megohms, while Fluke lists 40 megohms. Measuring current requires moving the lead to the correct fused jack and placing the meter in series. A voltage-style parallel connection while configured for current can create a dangerous short.

Choose the functions that match a documented procedure

Choose Fluke 117 for VoltAlert, AutoVolt and low-impedance troubleshooting within CAT III 600V. Choose MM420 for temperature, duty-cycle, Lead Alert and its included thermocouple within the same category ceiling. Neither product should be selected from brand familiarity alone when the actual job requires another category, range, accessory or specialty instrument.

Confirm the exact 117 or MM420 in the Amazon listing because nearby Fluke and Klein meters have different ranges and functions. Check condition, seller, included accessories, return terms and warranty eligibility. For non-electrical workshop layout, the laser-level and sander comparisons cover lower-risk tools with different selection criteria.

Official sources and further reading

Sources reviewed on September 26, 2026. Prices, availability and terms can change; recheck before buying.

Related reading

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