Clamp meters and multimeters / Klein Tools
MULTIMETER

Klein Tools MM420 multimeter

Checked 2026-10-18 against Klein Tools' US product page by Rob, licensed electrician

The Klein Tools MM420 is a multimeter, sold on its own. Klein Tools publishes CAT III 600 V safety rating, 600 V DC voltage (max range), 600 V AC voltage (max range), 10 A AC current (max range). In the box: Multimeter, Test Leads with CAT III/CAT IV Safety Caps, Thermocouple, Instructions, 2 x AAA Batteries. Source: Klein Tools' US product page, checked 2026-10-18.

Key specs

Safety rating (IEC 61010 CAT)
CAT III 600 V
DC voltage, max range
600 V
AC voltage, max range
600 V
AC current, max range
10 A
DC current, max range
10 A
Display resolution
4,000 counts
Resistance, max range
50 MΩ
Batteries (cells)
2 x AAA

Not on Klein Tools' US product page for the MM420: True-RMS; Low-impedance (LoZ) mode; Warranty. We do not guess.

What is in the box with the MM420?

  • IncludedMultimeter: Multimeter
  • IncludedTest leads: Test Leads with CAT III/CAT IV Safety Caps
  • IncludedBatteries: 2 x AAA Batteries
  • Not listedCase or holster: not in the maker's box list
  • IncludedAlso in the box: Thermocouple
Find MM420 prices on Amazon Find MM420 prices at Acme Tools Find MM420 prices at eBay New tab, US retailers. Search results open where no exact listing is on file. Check the listing says MM420; marketplace sellers vary.
  • US retailer, ships from the US
  • Free shipping over $199
  • Family owned since 1948
  • Acme Tools, as published on its site, checked 2026-10-17

Klein Tools MM420 specifications

Safety rating (IEC 61010 CAT)
What this means

Under IEC 61010, the category reflects location and transient risk: CAT II for plug-in equipment, CAT III for building wiring and panels, CAT IV for the service entrance and utility supply. The voltage is the working voltage at that category. The lowest-rated part (meter, leads or probe) sets the limit.

CAT III 600 V
DC voltage, max range
What this means

This is the highest DC voltage the meter can display, relevant to batteries, controls, solar arrays and automotive work. Solar strings can run well above residential voltages, so check the range covers your systems. As with AC, the range is separate from the CAT safety rating.

600 V
AC voltage, max range
What this means

This is the highest AC voltage the meter can display. It should comfortably exceed what you test, such as 120/240 V US residential or 277/480 V commercial. The measurement range is not the safety rating; check the CAT rating for where the meter may be used.

600 V
AC current, max range
What this means

This is the highest AC current the meter can read, in amps. Clamp and fork meters measure through the jaws without breaking the circuit; multimeters usually need wiring in series through a fused input with a much lower limit. Choose a range comfortably above the loads you work on.

10 A
DC current, max range
What this means

This is the highest DC current the meter can read. Many clamp meters measure AC only, so a DC figure matters for solar, battery, automotive and DC motor work. On multimeters, DC current is usually measured in series through a fused input. A blank entry may mean no DC current function.

10 A
Display resolution
What this means

Display counts set how many digits the meter can show. A 6,000-count meter reads up to 5999 before changing range, so it shows 240.0 V, while a 2,000-count meter would show 240 V. More counts means finer resolution, not necessarily better accuracy, which is a separate spec.

4,000 counts
Resistance, max range
What this means

This is the highest resistance the meter can read, in ohms, kilohms or megohms, covering continuity, heater elements, motor windings and sensors. Always measure resistance with the circuit de-energized. This range is not an insulation test; that needs a dedicated insulation tester (megohmmeter).

50 MΩ
Batteries (cells)
What this means

This lists the cells the meter or tester runs on, such as AA, AAA or 9 V. Common sizes are easy to find on the job. A low battery can cause inaccurate readings on some meters, so replace cells when the low-battery indicator shows.

2 x AAA
Capacitance, max range400 μF
Frequency, max range50 kHz
Temperature measurement-40° to 1,832°F (-40° to 1,000°C)
Min/Max recordingYes
Drop protection6.6 ft (2 m)
Size6.41 x 3.16 x 1.78 in (L x W x H)
Weight8.2 oz (232 g)
UPC barcode092644693748

Ratings are Klein Tools' published figures from its US product page, listed under Sources. Anything not on that page is left out rather than guessed. Check this against another model.


Find the MM420 at Amazon

Quick answers about the MM420

What is the MM420's safety (CAT) rating?

Klein Tools rates it CAT III 600 V. CAT IV covers the service entrance and utility side, CAT III distribution-level circuits such as panels and feeders; the lower of the meter's and the test leads' ratings is the one that applies. See our CAT ratings guide.

Does the MM420 measure DC current?

Yes: Klein Tools lists a DC current range up to 10 A.

What batteries does the MM420 use?

2 x AAA (dry cells; no tool battery platform).

Does the MM420 come with test leads?

Yes: Test Leads with CAT III/CAT IV Safety Caps.

Owner reviews

Read the owner reviews on KleinTools.com

Videos from Klein Tools

Klein Tools Digital Multimeters (MM325, MM420, MM450, MM720) · Klein Tools official YouTube channel

MM420 manuals and official documents

Sources

  1. Klein Tools US product page MM420, retrieved 2026-10-18

Spotted a wrong number? Report a spec error (opens an email with the model filled in). We re-check against the maker's page and correct the page.

Researched by Rob, licensed electrician (Australia), 18 years on the tools. Found an error? Tell us.

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