Klein Tools MM400 Digital Multimeter Review

Multimeters from Klein are one of the best affordable brands any electrician would like to have. The American brand was established in 1857 and manufactured some of the most accurate, reliable, and durable devices. It can measure temperature, frequency, and capacitance.

Since it’s an auto ranging multimeter, it will give the user an easy time working on different electrical connections. But what are the features and specifications of the Klein tools mm400?

Here’s an in-depth review of this product.

Klein Tools Mm400 Digital Multimeter Review in Detail

Product Summary

Klein mm400 is an inexpensive multimeter manufactured for electricians. It uses AAA batteries which are cheaper than the 9v. Mm400 can test for voltage of up to 600AC/DC, current of 10A AC/DC, and a resistance of 40m.
It has a backlit screen with a 4000 count, and it’s a Sans bar graph that lights up in darker areas. If there’s wrong connectivity on the continuity, it will produce beeping sounds as a warning.

Also, it has a low battery indicator, making it an effective device as one gets to change them on time. Replacing the batteries is also not a big challenge as it’s got a different compartment that’s easy to access.

The Klein mm400 meter comprises a plastic body that can withstand wear and tear. The strong body can also resist an impact of about 1 meter when it accidentally falls, making it last longer. This safe to use device has a safety rating of CATIII and CATIV, ensuring you’re safe while at work.

The compact design of this device makes it a portable device that won’t give the user challenges carrying or storing. The auto-ranging capabilities of Klein tools mm400 make it an easy-to-use device, while the clearly labeled dials and dials enable the user to have an easy time using them.

Build Quality

Klein brands are known for high-quality testers, which ensures they last longer. The mm400 has a rugged rubber holster that can withstand a 1-meter fall.

The strong flip-out stands and rubber feet also increase its durability, preventing the device from unnecessary falls and mishandling. Related Article: Best multimeter for the money

The bigger rubbery buttons and dials enable it to be operated with one hand. The Klein mm400 has a different battery compartment that the user can access with ease.

However, this device doesn’t have a high-resolution screen; it’s backlit for operation in darker areas. Its frequency changes three times every second.

Function and Performance

Although these multimeter experiences lag with capacitance and continuity, this is common with multimeters under 100. Klein mm400 has min/max buttons that help manage the high and low values. It also has a hold function to store the results for future reference instead of writing them.

The range button helps change the device to manual ranging. It’s capable of shutting off automatically, which makes it a battery saver. It takes 15 minutes before going off.

Safety and Protection

Klein mm400 has two fuses; one is for the high 10A current circuit, and the other is for the 500mA on the main terminal. What makes it a high safety device is the ceramic HRC type fuses. It also has a CATIII @600 safety rating which gives over-voltage protection to 6Kv.


  • Its high quality and durable
  • It’s got a thermocouple
  • It’s easy to use
  • It allows for auto-ranging capabilities and microamps
  • It’s has a compact design and affordable


  • It doesn’t have a protection case
  • It doesn’t have a true RMS technology

What’s Included in The Package?

Who’s This Multimeter For?

The Klein mm400 is the best device for engineers, electricians, and DIYers working on standard electrical connections and a tight budget.

What makes it stand out is that it can work on an HVAC system as it’s got a thermocouple. Beginners will also love this device as it’s easy to use. All the user needs to do is follow the instructions in the manual and work with fewer challenges.

What Makes This Multimeter Stand Out?

Although this is a China-made product, it’s of high quality according to Klein’s standards. The production location is only to reduce manufacturing costs.

It also has a thermocouple which enables the user to test for temperature making it a multifunctional device.

Users Reviews

If you look at the reviews section about this product, you’ll realize it has more positive reviews on amazon than negative ones.

For example, Mr. D from the USA says,

“I like the auto-ranging function on this multimeter. I Will only be seeing occasional use, so I read some reviews and weighed up the options on deciding what multimeter to buy. So far very pleased with this unit”

Another user says,

“Nice meter for the price. At first, I didn’t think the backlight was working, but you have to hold the button for a second, and it comes on”

These and many more positive reviews on this product should give you a reason to buy the multimeter and enjoy using it.

Final Thoughts

Getting a high-quality multimeter under 50 is never easy. However, Klein tools mm400 does have the most outstanding features, which makes it deliver. It’s best for an engineer or DIYer on a tight budget.

It can test for resistance, capacitance, temperature diode, and voltage. But it doesn’t have true RMS technology and is not the best for use while working on sensitive electronics.

Scroll to Top