Klein ET270 vs MM420: My Real Test Results

I tested the Klein ET270 and MM420 side by side. I used them on real jobs to see which one works best. Here is what I found after weeks of use.

Klein Tools ET270 Review

I started with the ET270. It is a unique tool. It is not just a standard meter. It feels like it was made just for home wiring.

I noticed the test leads first. It has a special cord with a plug on the end. This is different from most meters.

I took it to a job to check outlets. I had to check twenty of them. This tool made it fast. I did not use standard probes. I just plugged the cord in. The screen lit up fast. It showed me the voltage. It also checked the wiring. It said “Correct” right on the screen.

One outlet had a fault. The screen turned red. It warned me about an open ground. This saved me time. I did not have to guess. The tool told me the answer.

I liked the size too. It fits in my hand well. The dial is simple. It does not have too many settings. This is good for quick work.

I also tested the battery setting. Most meters just read voltage. That can be wrong. A bad battery can look good until you use it.

The ET270 puts a load on the battery. I tested a box of old AA batteries. I found one I thought was good. The meter showed it was “Poor.” This is a great feature. It tells you the truth.

But I did have a problem. I tried to fix a heater. I needed to check the current. The ET270 cannot do this. It has no setting for amps. It is only for voltage. It could not help me with the heater motor.

Klein Tools MM420 Review

Next, I used the MM420. This feels like a real multimeter. It is thick and tough. It has rubber all around it. It feels like it can take a drop.

I saw the extra jacks at the bottom. This meter can measure current. That is a big plus.

I used it on an HVAC unit. The fan was not working right. I needed to check the capacitor. This part helps the motor start. The MM420 has a setting for this.

I put the probes on the part. The meter thought for a second. Then it showed me a number. The part was good. The other meter could not do this test.

I also tested the current. I moved the red probe. I put the meter in line with a fan. It showed me the amps. The number did not jump around. It was steady. This helps when you look for problems.

I also used the temp probe. I checked an air vent. I plugged the wire in. The reading went up fast. It was nice to have this. I did not need another tool.

But checking outlets was slower. I had to use two hands. I had to hold both probes. I had to look at the number. It did not just say “Good” or “Bad.” You have to know what the number means.

Details Comparison for Klein ET270 vs MM420

Here is how they compare. I looked at how they work on real jobs.

Core Capability Comparison

The main difference is what they can do. One is a full meter. The other is a tester.

If you work on motors or fans, you need the MM420. It measures Amps. The ET270 cannot see current. But for wiring, the ET270 is faster. The MM420 does more. It checks heat and capacitors. It is a better value for a pro. The ET270 is just for checking live wires.

Outlet Testing Workflow

I checked how easy it is to test plugs. This is a job I do a lot.

The ET270 was very fast. I just plugged it in. I looked at the screen. It told me the answer. I did a whole room in minutes.

The MM420 was slower. I had to hold two probes. I had to make sure they touched the metal. Then I had to read the volts. It took more work. The ET270 is much better for this.

Accuracy and True RMS

I tested them on a dimmer switch. This changes the power flow.

The MM420 is a “True RMS” meter. This means it is smart. It reads weird power waves well. My reading was steady. It matched my best tool.

The ET270 is basic. On normal power, it was great. But on the dimmer, it was off a bit. For home wiring, this is fine. For electronics, the MM420 is better.

Display and Interface

The screen matters a lot. You need to see it in the dark.

The ET270 has a black screen. The numbers light up. I could see it in a dark basement. It uses words like “Open Ground.” That is easy to understand.

The MM420 has a grey screen. It is clear. But in the dark, I had to use the light button. The screen is busy. It has lots of symbols. The ET270 is simpler.

Battery Testing Reliability

I hate guessing if a battery is dead. I tested some AA batteries.

The ET270 puts a load on them. It makes the battery work. I tested a weak one. The screen showed it was bad. It gave me the truth.

The MM420 just checks volts. That same weak battery looked good on it. It showed 1.4 volts. But it died in a flashlight. The ET270 is better for this.

Read More: Klein CL800 vs Fluke 325

Conclusion

If you check outlets and batteries at home, buy the Klein ET270. It is fast and easy. If you fix appliances or fans, buy the Klein MM420. You need it to measure Amps. The other one cannot do that job.