Megger Insulation Tester - Review

Table of contents

RoadTest: Megger Insulation Tester

Author: nontheist

Creation date:

Evaluation Type: Test Equipment

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: To a certain extent, standard multi-meters are also comparable to his product as most of the functionality is duplicated.

What were the biggest problems encountered?: I didn't have any problems.

Detailed Review:



There were no real surprises here.  The carrying case is enclosed in a small cardboard sleeve with a feature comparison chart versus other MIT 400 series models.  It's listed as an insulation and continuity tester but carries a number of other features I'm not used to seeing on an insulation tester (more on this later!).  To see the specs, see here:


Included in the package:

  • a very sturdy carrying case with two clasps
  • The Megger
  • Two standard leads
  • One lead with integrated 'test' button - more on that later
  • A disk with user guide and the e-book 'A Stitch in Time' - an excellent resource
  • A certification/calibration sheet (good for ~1 year)




Using the MIT420/2

The test lead ports are at the top of this unit.  It comes with a red lead and a black lead, exactly like you would expect.  There are interchangeable test lead tips for alligator clips or a pointed tip.  Included is also a 2nd red lead that includes an integrated 'test' push button.  The normal method for using this megger is to attach your leads and then push the yellow test button.  To lock in the test you'd press the yellow test followed by the red lock button.  You can also use the pre-programmed polarization index test or dielectric absorption ratio.  If you need a 'quick' test in a tight area the included red lead with 'test' push button would be very useful for you.  This lead allows you to perform a test without having to push the yellow button on the main unit.


This unit has what is called 'Stabilised insulation test voltage', so you can be sure that your tests are as accurate as possible (2% voltage vs. 10-20% for other insulation testers).  During my use the voltage approached the test voltage and didn't have any overshoot. My use case doesn't require that much accuracy but it is a feature worth mentioning.


The main unit has a very rugged feel.  The grey body has a very slight rubberized feel and is very easy to keep your grip.  During my first week of use, I was tasked with testing a very oil leak prone air compressor.  It was impossible to keep from having to set this Megger in some oil.  This unit handled the oil like a champ.  Most of the other types of testers I have end up discolored due to the abuse that we inflict on them but this tester cleaned right up.  It has an IP54 weatherproof rating as well. I didn't have any rain during my testing and I'd rather not have to try to megger a motor in the rain but if I had to, this would be the unit I'd bring along.


The screen has optional backlighting which is surprisingly bright.  The text is large and clear and the light is a white/blue when backlit.  Too many of our industrial areas suffer from poor lighting.  I have a 'yellow' brand tester that doesn't include a backlight.  It's one of those features that you didn't realize you wanted until you needed it. 


Test results can be stored on internal memory on a per-register basis.  (i.e. first test goes in register 1.  next test is in register 2).  Navigation is very straight forward using the up/down/left/right arrows that are just below the display. 


The MIT420 is capable of insulation resistance testing, voltage measurement, continuity/resistance, and capacitance testing.  None of the other units that I have are as capable as this one device.  I almost want to take my yellow multimeter meter out of my bag and just take this with me all the time now.  I've too often thought about grabbing an insulation tester after I'm already in the field.  This tester has everything I want in a neat little package.


Retrieving saved results

A megger isn't worth anything if you don't save your results for later comparison.  Saved tests are stored sequentially.image


The type of test is displayed, in this case a DAR:image


Using the up/down buttons you can see the T1 value, T1 voltage, T2 value, and T2 voltage.  Test times are adjustable in the setup menu.imageimage





One real world test with pics

Because all of the motors I tested at work had results that were 'too good' I had to find something that didn't peg out >100Gohm.  I had a failure of my A/C compressor wiring.  I didn't have the Megger when this picture was taken.  I hastily cut out the bad section of wire and spliced everything back together to get through the heat of summer.



Time to replace the damaged wiring.  The new wiring was quite a bit longer than the original and was heavier gauge wire.  You can see the black tape around the splice on the original wiring


This is a test of the compressor and wiring after replacement of the motor cables.  I realize now I should have pulled the screen protector to get a clearer image.  This is 34 seconds into a DAR at 250V.  Ended up with a DAR of 1.6 which is quite good.




Final Thoughts

I was able to use this Megger during a maintenance outage at my job.  I had tested multiple motors during the outage and it was really great to have a Megger that was this small and portable. Motor failures are inevitably going to occur and this is the right tool to have when you need to test for it.