Electronics > Beginners

Which new Multimeter i should buy

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mvs:

--- Quote from: Irukandji on January 31, 2019, 06:57:34 pm ---How can i know if the CAT certification true or not true on a multimeter. Is there any way to read if it true or not or did no one check the CAT certification like TÜV/DEKRA in germany?

--- End quote ---

You may have a look at youtube channel of Joe Smith. He has tested a lot of DMMs using transient generator, incl. Uni-T UT139C, EEVBlog Brymen BM235, etc.



rstofer:
People get all hung up on CAT ratings without realizing that we got by for many decades before this new 'standard' was invented, probably by Fluke.  Yes, a high end meter from a high end company (Fluke) probably does comply with the standard (is it really a legislated standard?).  Perhaps others do as well - but you pay for the rating and the name.  There was even a time when V-O-Ms didn't even have fuses!

CAT ratings simply aren't necessary for breadboard work and only CAT III 600V is necessary for working at the level of a wall outlet.  I don't trust any Chinese meter rating regardless of who has branded the meter.  Maybe they comply, maybe they don't.  Colored ink is cheap!

Here's the thing:  You only need to worry about CAT when there is some kind of high voltage transient condition - like a lightning strike right outside your house.  How about just make a rule:  No testing of wall outlets during a storm.  Read the Fluke article on CAT ratings:

https://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf

In most cases, you can get by with CAT II.

Check out Dave's review of the Aneng 8008.  You will find that it is superbly accurate and dirt cheap.

https://www.eevblog.com/2017/07/15/eevblog-1007-is-a-25-multimeter-any-good/

I have a few DMMs:  Fluke 189 (expensive), Vichy 97 (decent meter), EEVblog BM235, EEVblog 121GW and the Aneng 8008.  I really like, and use, the 8008.  The two EEvblog meters are on the bench but generally not used, the other two are stored away.  I also have a couple of those really cheap Harbor Freight meters.

The AN8008 is so inexpensive that you can probably get 2 or 3 and this would be ideal.  Three meters is about right for most prototype work.

Why measure outlet voltage?  Is there anything you can do to change it?  If not, who cares what it reads?  Test for presence with a wall wart with LED or a table lamp or whatever.  And don't do it when lightning is in the neighborhood.

rstofer:

--- Quote from: Yolk on January 31, 2019, 06:49:06 pm ---I have the fluke 107 and it's a great meter,it's almost twice your budget but hey,it's fluke brand. You can search for pictures of the insides and see for yourself.. you really get what you pay for.

Caps goes to 1000uF that's my only problem,i wish it would go to 10k like the 87'V but i doubt you'd be testing those often.

--- End quote ---

Use a scope and watch the change in voltage for a series RC circuit.  Vout = Vin * (1-e-t/RC).  10,000 ufd and 1k has a time constant of 10 seconds.  The output voltage will rise to about 63% of the input voltage in 1 time constant.  In fact, this is so slow it might be possible to watch it with a DMM, certainly with a V-O-M.  Put 5V in and expect 3.15V in 10 seconds.  If I did the math right...

rstofer:
Why 3 meters?  Consider a simple common-emitter transistor amplifier.  Maybe you want to characterize the transistor by using 1 meter to measure collector current by a) putting the meter in series with the collector or b) measuring the voltage drop across the collector resistor and computing the value.  Next, you would want to measure Vce and Vbe.  In a perfect world, these three measurements would be taken simultaneously.

Yes it can be done with a lesser number of meters but then it isn't a perfect world.

mvs:

--- Quote from: rstofer on February 01, 2019, 07:21:44 am ---People get all hung up on CAT ratings without realizing that we got by for many decades before this new 'standard' was invented, probably by Fluke.  Yes, a high end meter from a high end company (Fluke) probably does comply with the standard (is it really a legislated standard?).  Perhaps others do as well - but you pay for the rating and the name.
--- End quote ---
Yes it is legislated standard, IEC-1010 was adopted as EN 61010 and UL-3111 in Europe and US.

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