Klein mm400 Review 2024 [Auto-Ranging Multimeter ]

Multimeters had changed a lot from when they were first discovered. The first multimeters were hard to read as they were analog. In the past, only experts could use and read the results. Digital multimeters have made reading of the results to be easy and quick.
Since there are lots of multimeter brands to choose from, it is crucial to know which brands offer reliable multimeters and which ones don’t. Klein is one of the most reliable multimeter brands and is well-known for its affordable price. This is an American brand that was established in 1857. It offers some of the most durable, accurate, and safe multimeters on the market. In this Klein mm400 review, we are going to discuss the Klein mm400 multimeter.

Klein Tools mm400 Review (Video):

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Summary of Contents

The mm400 digital multimeter is sturdily built and has auto-ranging. In addition, the device meets the CAT III 600V safety rating. It has a battery level indicator that warns the user when the batteries become low. The multimeter is very easy to use with well-labeled buttons and an easy turn the knob. To use the device, insert 2 x AAA batteries in the easily accessible battery compartment and carry out different tests. It can measure AC voltage, resistance, temperature, capacitance, continuity, test-diodes, duty-cycle, and frequency.

Technical Features Of The Klein mm400 Multimeter


Klein mm400

Display: 3 ¾ digit, 4000 Count LCD backlit display
Storage temperature: 14°F to 140°F (-10°C to 60°C)
Diode test: 1.5 mA max, open circuit voltage 3.0V DC
Continuity Check:Audible signal <50Ω
Frequency Sampling:3 samples per second
Overload: “OL” indicated on display, overload protection 600V True RMS in all settings
Polarity::“-” on display indicates negative polarity
DC volts: Test Ranges: 400.0mV, 4.000V, 40.00V, 400.0V, 600V on DC current
Resolution: 0.1mV, 1mV, 10mV, 100mV, 1V
Accuracy: ±(1.0% + 8 digits), ±(1.2% + 3 digits), ±(1.5% + 3 digits)
Input impedance: 10MΩ
Overload protection: 500mA / 600V and 10A / 600V two Fuses
Frequency Range: 50 to 60Hz
AC volts: Ranges: 4.000V, 40.00V, 400.0V, 600V on AC current
Resolution: 1mV, 10mV, 100mV, 1V
Accuracy: ±(1.2% + 5 digits),
±(1.5% + 5 digits),
±(2.0% + 5 digits),
±(1.0% + 8 digits),
±(1.2% + 3 digits),
±(1.5% + 3 digits)
Input impedance: 10MΩ
Overload protection: 500mA / 600V and 10A / 600V Fuses
Frequency Range: 50 to 60Hz
Price: buy mm400 klein toolCheck Price

Product description of mm400 multimeter

  • Powered by 2 x AAA batteries
  • Durable plastic body
  • Rubber feet for better grip & flip outstand
  • Auto-ranging multimeter
  • Klein mm400 tests a car battery
  • CAT III 600V and CAT IV safety rating
  • Low battery indicator & Sans bar graph
  • Overvoltage protection
  • Measure temperature, volts, ohms, capacitance, frequency, and continuity of sensitive electronics
  • Large bright backlight display
  • Better multimeter safety precaution feature
  • Buttons, dials, and ports

Benefits of using Klein tools mm400

Let’s check the in-depth review of this professional-grade multimeter-

Sturdy construction

The Klein multimeter mm400 is a reliable multimeter and is suitable for construction sites or any tough surroundings. The gadget is made of a sturdy plastic body that can resist an impact of up to 1 meter when dropped accidentally.
klein tools mm400 reviewCheck Price

Whether you are an electrician or DIY enthusiast, this device will serve you for over a long period of time. It can get crushed or fall accident, but it will still deliver accurate readings.

Related article: Fluke vs Klein: which multimeter brand offers a  better price?

Safe to use

One of the additional features that separate Klein multimeters from most multimeters brands is that they are safe to use. The Klein mm400 multimeter is safe to use with its ratings of CAT III 600V and CAT IV. This prevents the device from harming you. Thus, you can use it knowing that it is safe.

Compact design

The multimeter’s wonderful design helps the user have an easy time carrying out different tests and measurements. It fits perfectly in the hand of the user, and it can be easily kept in a backpack. Also, it has molded-in tests, lead holders. With its compact design, you can be certain that it will fit well in tight places. Also, the price is lower than the Klein mm600 auto-Ranging 1000V digital multimeters.

Easy to use

If you have been having a difficult time using advanced DMM, this is not the case with the Klein mm400 multimeter. The auto-ranging multimeter has a simple-to-use interface. The buttons and dials are clearly indicated and very easy to use. Also, the ports have clear signs for the easy insertion of test leads. In addition, it has a large backlight display screen for showing results from tests conducted in a lit place or in a dark area.

Comfortable and easy to handle

Another great attribute about the Klein mm400 multimeter is that it is easy to handle and very comfortable.
Auto Ranging Digital Multimeter mm400Check Price

You don’t need to hold it with two hands as just one is enough. Also, it has a nice design that fits well in the palm of your hands. This makes testing, troubleshooting, and reading to be easy.

Related article: Check the technical specification of Fluke 174 True RMS multimeter

Low-level battery indicator

2 x AAA batteries power the mm400 auto-ranging multimeter. These are included in the purchase. Also, it has a low-level battery indicator that assists the user in checking the battery percentage. This will help you to be ready with spare batteries in case they run out during use.

Great price

Despite having outstanding features and carrying out accurate readings, this multimeter is offered at a great price. So, this is a great bargain for those who want a reliable and durable automotive multimeter for long-term use.

Setbacks of Klein mm400

Klein mm400 vs. mm600

Difference between mm400 and mm600.


Klein mm400

Klein mm600

Batteries: AAA 2 x batteries are required. AAA 2 x batteries are required. (included)
Voltage AC/DC: 600 volts 1000 volts
Ohms(Resistance): 40 MΩ 40 MΩ
Capacitance: 40nF – 200µF 40.00 nF – 4000uF
Frequency: 10Hz – 50kHz 1Hz – 50 KHz
AC/DC Current: 10 A 10 A
Battery Cell Type: Alkaline Alkaline
Batteries Included?: No Yes
Type & volts: DMM, Auto-Ranging, 600V Digital Multimeter, Auto-Ranging, 1000V
Size: Auto Ranging/Temp, Cap, Freq Standard
Item Weight: 10.6 ounces 10.6 ounces
Product Dimensions: 1.8 x 3.1 x 6 inches 10 x 5.6 x 2.7 inches
Review: Detail Reviews link Klein mm600 review
Price: Auto Ranging Klein multimeterCheck Price Check Price

Final Thoughts

The Klein mm400 digital multimeter is a sturdy device that is ideal for engineers, DIYers, and electricians. Like Fluke DMM 101 and Craftsman digital multimeter, this is the perfect digital multimeter for beginners, DIY enthusiasts, and professional electricians. The DMM has the ability to perform a wide range of tests such as voltage, current, resistance, frequency, continuity, test diodes, temperature, capacitance, and duty-cycle. The device can absorb impact up to 1 meter and has a safety rating of CAT III 600V with the protective rubber holster. When the battery becomes low, the battery level indicator will alert you by showing the battery level. This is an amazing DMM for startup engineers. I hope our Klein mm400 reviews will have given a clear idea about this quality multimeter. Comment below if you have any questions about this mm400 multimeter.


  • Where is the Klein mm400 multimeter made?

The multimeter is made in China. However, they are well-made and suitable for use anywhere.

  • Who should buy mm400 from Klein?

The multimeter is ideal for both residential and automobile use. It can also be used for light industrial use.

  • Is a carry case or cover included?

No, you have to buy it separately. It would cost an extra $10.

  • Can you measure LoZ voltage?

No, you can’t measure the low-impedance input of a circuit.

  • Can the Klein mm400 test AGM batteries?

Yes, a fully charged AGM battery should have 12–13 volts.

  • How to test a battery with a Klein mm400 multimeter?

-Charge the battery fully.

-Get a battery load tester.

-Connect the probes to the battery.

-If it drops below 12 volts, the AGM battery gets damaged.

  • Can it test a live capacitor?


  • How to use the Klein mm400 multimeter?

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