Klein MM420 vs MM720

Keep or buy the Klein MM420 for everyday home and hobby checks; choose the MM720 when your work specifically needs LoZ, its higher category/voltage ratings, or a larger capacitance range. Both are auto-ranging True RMS meters with temperature and microamp functions, so those features alone do not justify replacing an MM420. The useful upgrade is a measurement task your existing meter cannot cover, rather than the larger model number.

Quick picks: what would the upgrade enable?

Compare specifications and all conditions

Working MM420; routine voltage, continuity, temperature and µA checks

Pick

Keep MM420

Reason

These functions are already present

Need low-impedance ghost-voltage troubleshooting

Pick

MM720

Reason

Adds an AC/DC LoZ setting, limited to 600V

Need capacitance above 400 µF

Pick

MM720

Reason

Extends the specified ceiling to 6000 µF

Want a tighter basic DC-voltage specification

Pick

Keep comparing

Reason

Their lower DC-voltage ranges share ±(0.5% + 5 digits)

Buying primarily for frequency above 50 kHz

Pick

Resolve the documentation first

Reason

Klein's MM720 frequency specifications conflict

Full comparison table ↔

Swipe to compare. Row labels stay visible.

Your situation	Pick	Reason
Working MM420; routine voltage, continuity, temperature and µA checks	Keep MM420	These functions are already present
Need low-impedance ghost-voltage troubleshooting	MM720	Adds an AC/DC LoZ setting, limited to 600V
Need capacitance above 400 µF	MM720	Extends the specified ceiling to 6000 µF
Want a tighter basic DC-voltage specification	Keep comparing	Their lower DC-voltage ranges share ±(0.5% + 5 digits)
Buying primarily for frequency above 50 kHz	Resolve the documentation first	Klein's MM720 frequency specifications conflict

Your situation	Pick	Reason
Working MM420; routine voltage, continuity, temperature and µA checks	Keep MM420	These functions are already present
Need low-impedance ghost-voltage troubleshooting	MM720	Adds an AC/DC LoZ setting, limited to 600V
Need capacitance above 400 µF	MM720	Extends the specified ceiling to 6000 µF
Want a tighter basic DC-voltage specification	Keep comparing	Their lower DC-voltage ranges share ±(0.5% + 5 digits)
Buying primarily for frequency above 50 kHz	Resolve the documentation first	Klein's MM720 frequency specifications conflict

The MM420 manual and currently linked MM720 manual support the function and range comparisons below. The frequency conflict is detailed later.

MM420 vs MM720: the comparison table

Sources: the manuals above and Klein's MM420 product specifications, MM720 product specifications and current selection guide. These are manufacturer specifications, not readings obtained by thisMETER.

The displays have 4000 counts on MM420 and 6000 on MM720. That changes where ranges switch; it does not, by itself, establish measurement accuracy.

• 4000 countsMM420 display, per Klein
• 6000 countsMM720 display, per Klein

Best to keep for everyday checks: Klein MM420

The MM420 is our default when you want a good multimeter for basic checks and already know its ranges cover the job. Its combination of True RMS, temperature, capacitance, continuity and dedicated µA/mA ranges means the MM720 is not necessary simply to add those functions. The illuminated input jacks are also a useful buying distinction: MM720 substitutes a screen reminder.

Keep it for electronics or lead-based HVAC microamp work when its range and accuracy meet the service requirement. Its limitations here are the absence of a listed LoZ mode, the CAT III 600V rating and the smaller capacitance ceiling. A different thermocouple may solve a probe limitation without replacing the meter.

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Upgrade for LoZ and wider ranges: Klein MM720

The MM720 earns its place for low-impedance voltage troubleshooting and work requiring its CAT IV 600V / CAT III 1000V ratings. Its reverse-contrast display has optical backlight control, and its REL function displays a change relative to a reference measurement. Those are practical differences from the MM420's listed controls.

For capacitor checks, moving from 400 µF to 6000 µF is a documented range upgrade. For fine current checks, the gain is more subtle: the lowest range extends further and the DC accuracy's digits term improves, while the smallest display step stays the same. Neither is a reason to promise better results on every function.

Check the exact MM720 package with Klein

Resolution and stated accuracy: compare the actual range

Klein expresses accuracy as ±(% of reading + least-significant digits). The percentage term and the value of each display digit both matter. The tables state accuracy at 18–28°C, with temperature corrections outside that interval.

For ordinary car-battery voltage checks, both use 10mV steps on their respective 40.00V and 60.00V DC ranges, with the same stated accuracy formula. That is a concrete reason to keep an MM420 rather than assuming more counts improve every reading.

There is a resolution advantage near a range boundary: MM720 retains 1mV steps on its 6.000V range, while MM420's next range above 4.000V is 40.00V, resolving 10mV. Buy that difference when your circuit needs it.

For DC microamps, both resolve 0.1 µA. MM720's smaller digits term improves the stated allowance on that range, but the tables do not state burden voltage. Ask Klein about that specification if meter loading could affect the circuit. These distinctions follow the manual rows, not a bench comparison.

AC qualification: MM720's voltage table labels its accuracy 50–60 Hz, while the same section lists a 50–400 Hz frequency range. Do not extend the stated AC accuracy across that entire band without clarification from Klein. MM420's voltage table lists 50–400 Hz.

LoZ, input ratings and current limits

MM720's LoZ setting is intended to identify ghost or stray voltages. Its manual specifies input impedance greater than 3 kΩ, versus 10 MΩ for normal voltage measurement; do not rewrite that as an exact 3 kΩ specification. Crucially, LoZ is limited to 600V, even though normal voltage measurement reaches 1000V. The manual also lists 600V maximum input for its resistance, capacitance and frequency functions.

Category matters alongside voltage. Klein defines CAT III as the distribution part of a building's low-voltage mains installation and CAT IV as its source. MM420's CAT III 600V rating does not become CAT IV because its included leads have CAT III/CAT IV caps.

Both meters specify 10A, and both manuals recommend measurements above 6A last 30 seconds, followed by 10 minutes of recovery. MM720's 600mA measurement limit and 800mA/1000V protection fuse are different specifications; the fuse rating does not create a larger measurement range. MM420 likewise separates a 400mA limit from its 500mA/600V fuse.

Temperature, capacitors and the frequency conflict

Temperature alone is not an upgrade reason. Both meter inputs cover −40 to 1000°C, with 1°C resolution, but both supplied K-type thermocouples are suitable only below 180°C. For hotter work, budget for an appropriately rated probe; the meter's headline range does not describe the included probe.

Capacitance is a real range gain. MM420 starts at 40.00nF and ends at 400.0 µF; MM720 starts at 60.00nF and ends at 6000 µF. Both lowest ranges resolve 10pF. Choose MM720 for the larger ceiling, rather than assuming finer small-capacitor detail.

Frequency remains unresolved. The MM720 manual reaches 500.0kHz, and its product page says 1 Hz–500 kHz. However, the selection guide currently linked from that page lists 10Hz–50kHz for MM720. MM420's page similarly starts at 1 Hz, while that guide starts at 10Hz. Confirm the required frequency and signal conditions with Klein before buying for that task; we do not choose one conflicting claim as the guaranteed limit.

Standard packages, bundles and optional accessories

A carrying pouch is included with MM720; Klein lists a separate hard case as an accessory. Its magnetic hanger is also optional, as the family brochure makes explicit. Alligator clips are absent from the MM720 standard included-items list: confirm them separately in any advertised bundle.

Do not assume a neighbouring model is an accessory variant. The same brochure distinguishes MM450, which has a reverse-contrast display but lacks LoZ, from MM720. Check the model on the instrument and its supplied manual before comparing packages.

1. 1

   Identify the task

   Write down the function, required range and category/voltage rating before choosing a model.

2. 2

   Identify the package

   Match the meter model, capped leads, thermocouple, batteries and any promised case or clips.

3. 3

   Identify the extras

   Confirm the probe rating and whether a hanger or hard case is a separate purchase.

Klein's US buying-options page names MM720 and provides retailer routes. Check the exact package and availability before ordering.

How we choose

We compared Klein's US product pages, the manuals linked from them, package lists and selection documents. Recommendations reflect specified functions and limits; no physical testing informed this comparison. We preserve conflicts instead of merging incompatible specifications. See our selection method and the broader best multimeters guide.

Verdict

Keep MM420 when its existing functions cover your work. Choose MM720 for LoZ, the higher marked ratings or the larger capacitance range, after matching the exact task and accessories. If you need current through a jaw, compare tool types in clamp meter vs multimeter; use our beginner multimeter guide for the function basics.