Thursday, 12 September 2019

Which is the best digital multimeter?

I hope this blog will help you to quickly find the meter you are looking for without wasting hours on YouTube or Google as I have just been doing!

The EEVBlog BM235


Of course, your choice will depend on what you are looking for - CAT rating, safety and reliability, true RMS, accuracy, capacitance, frequency measure (and output), diode measurement, short-test beeper, temperature measurement, etc.

BTW: If you use my Amazon links below to buy then I will earn a small commission ;-).

Safety

Many meters are CAT rated (e.g. CAT III), but unfortunately it seems we must take these ratings with a large pinch of salt. If you have a cheap meter and leave it on the resistance range but then use it on a live mains-powered system, it probably won't survive. If you have it on the current or low voltage range and then connect it across the 110V/230V mains supply, this can also end in tears (and will also wake you up a bit too!).

I suggest that you look at the Joe Smith YouTube videos to get an idea of how to blow-up test these meters (see here for the final test video which includes dropping them from a great height onto concrete)!

In many cases, as well as blowing the fuse, an over-voltage or current 'spike' will permanently damage the components inside the DMM and also the rotary switch PCB tracks thus making repair impossible.

Joe Smiths safety tested 'passed' finalists were:
  • Fluke 101 $40  Fluke 107 $90
  • Amprobe AM-530 $65 or Amprobe AM-510 $70 (Fluke own Amprobe and should be tested to same standards as Fluke)
  • Brymen BM869S (v. nice meter but expensive - Joe Smiths favourite)

Note: The test video is 3 years old, so newer models may be a better choice now...

Features

I found this really useful webpage - you can sort the table by clicking on the column heading, you can hover over the thumbnail icons to see a larger picture of each DMM and hover over the link to see an instant table of all of the actual test results or just click on the link to see a full report - magic! His whole site at lygte-info.dk is also quite interesting too.

The lygte-info.de DMM table also contains actual safety ratings rather than the manufacturers 'guesstimate'.

MT108T Cheap as chips but versatile too!
Use the links at the top of the table to reduce the list by price or just click on 'good' and then sort by price.

My requirements included being able to measure capacitance accurately (and preferably in-circuit - which means the meter output measuring voltage waveform should be below 600mV if possible to get below diode junction voltage thresholds).

For a useful and cheap DMM, the Mustool MT108T $30 seems to have a nice range of features, however it may be pot-luck as to whether you get a 'good' one that will last years or not because according to some YouTube comments the quality can vary. The MT66 is even cheaper at $20.

Aneng meters (AN882B+ $20, V7 $35, V8 $40) are also good (cheap) options.

Many people on YouTube recommend the UNI-T UT191T $130, UT139S $90 or the cheaper UT139C $50 which have tested well for safety (check the table for other models, as not all UNI-T models passed the safety testing).

The Eevblog designed DMM (by Dave Jones) Brymen BM235 $130 - blue sleeve is the Eevblog version which has high quality leads and a temperature sensor - aka 121GW) and is, of course, worthy of serious consideration too. Get it from Dave if you are in Ozland here for AU$290. This is reviewed on lygte-info.dk here.

So the choice is yours - a $30 MT108T or a $130 BM235 or something in-between?

I have gone for the AM-510 because it is a good make and is difficult to blow up, but be aware that it only measures capacitors up to 100uF. However, I intend to purchase a separate capacitance+ESR meter because I continue to be amazed at the number of relatively new appliances that have bad caps! Oh, and I also need to repair my beautiful Tektronix 2465B 400MHZ oscilloscope (1989) which went BANG! last week and sent up smoke signals!

My old Tek 2465B in pieces!
If you can personally recommend a decent mid-priced modern DMM of good quality (preferably below $100 and available in the UK) then please let me know - although I am very tempted to just fork out for a BM235...)

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