Why CAT ratings are so important AND safe practises

[joeqsmith]

Joe Smith showed it's not THAT hard to make a very good performing front end.
So in a sense it would be possible to make a very good performing multimeter for just 25-30 bucks.

Joe never tests any meter on the current ranges.

From a safety standpoint, nothing I have shown could be considered an improvement.  The changes would need to be put to the test.  That's not free.   If you only sold one meter ever, that would be a lot more than $30 to recover your testing costs.  Start adding zero's behind it.. lol.   

I showed a highly modified UNI-T UT61E where I attempted to lower the  burden voltage and increase the current it could handle.   I did a fair amount of testing with it but not for safety. 

[Lightages]

The is not exactly on topic, but very relevant:

[vk6zgo]

WTF is that rambling stream of conscious rambling. What are you trying to say?

To quote Uncle Martin "You are a very redundant young man, young man!"

Yeah, I goofed up on some wording.  Thank you for being such a word nazi.

Nah! I'm only a "word Neo Con" at worst.
A real word nazi would have pointed out that you wrote "conscious" where you meant " consciousness".

[vk6zgo]

Be aware that quality isn't proportional to price.
I know some audio companies who sell the same boards for OEM and consumers.
Only the consumer prices are 6 timers higher.
The BOM is almost identical.

I have also seen other companies where I know the exact BOM (and therefore the production price).
They sell their stuff for a much much higher rate.
It's worse with companies that almost have a monopoly.

It's got nothing to do with quality (beyond basic product requirements), it's quantity - a market of 10s of thousands versus markets of millions and two manufacturers versus dozens.. An economist would discuss it in terms like 'economies of scale', 'price sensitivity of demand', 'duopoly', 'market entry costs' and 'effective competition'.

Another point is that historically, instrument manufacturers dealt mainly with businesses who bought them for use by employees.
To very large organisations, such as equipment manufacturers, Communications & Broadcasting companies, & the Military, the price of a few fuses, or indeed, a few multimeters would be lost in their other operating costs.

The large scale ownership by individuals of DMMs of a fair degree of sophistication is only a quite recent phenomenon, & the manufacturers are just continuing with their time honoured pricing structure.

[Z80]

One more thing I think worth to be stressed is the sense and alertness as well as attitude of safety. It's more than knowledge and equipment combined.

Yes absolutely, a little knowledge can be a dangerous thing.  The biggest dangers from your home electrics are shock and fire, HRC won't help you with those.  Even in the industrial world, arc flash / blast are fortunately quite rare because only trained professionals with the correct paperwork & permits are given the keys to the big stuff.  I looked at the UK RIDDOR stats (this is an official govt accident report system) and the biggest source of injury or death amongst electricians by a country mile is falling / tripping, arc flash doesn't even get a mention.

[HoracioDos]

In China we have a saying, kills the good fighters, and drowns the good swimmers.

Good to know! Here we say: Confidence kills a man and makes a woman to get pregnant

[madires]

Yes absolutely, a little knowledge can be a dangerous thing.

We call those people "experts with dangerous half-knowledge"

  The biggest dangers from your home electrics are shock and fire, HRC won't help you with those.  Even in the industrial world, arc flash / blast are fortunately quite rare because only trained professionals with the correct paperwork & permits are given the keys to the big stuff.  I looked at the UK RIDDOR stats (this is an official govt accident report system) and the biggest source of injury or death amongst electricians by a country mile is falling / tripping, arc flash doesn't even get a mention.

Over here a DMM with proper HRC fuses should be fine for home electrics because the main fuses are commonly 35A. They are located in a dedicated sealed box and may only be accessed by the electricity supplier or a licensed sparky. Anyway, I would use something like a Duspol for checking mains and a clamp meter for current measurements. In typical cases a DMM is simply the wrong tool for mains. And someone poking around in industrial environments should have a sound education for that kind of work.

[Assafl]

BTW - using a fake rating DMM or a non rated DMM (albeit I think ALL have maximum voltage - even the old ones - no?) is the same as using gadgets "made in china" (crap gadgets - not the good stuff). 

What about laptop bricks that have very little isolation (especially going to a nice metal case laptop)?

Some are worse like the water heater that just uses electrodes of 220v into a cup?

All of these can kill a beginner in much the same way a bad DMM can.

[Fungus]

All of these can kill a beginner in much the same way a bad DMM can.

Two wrongs don't make a right.

[b_force]

BTW - using a fake rating DMM or a non rated DMM (albeit I think ALL have maximum voltage - even the old ones - no?) is the same as using gadgets "made in china" (crap gadgets - not the good stuff). 

What about laptop bricks that have very little isolation (especially going to a nice metal case laptop)?

Some are worse like the water heater that just uses electrodes of 220v into a cup?

All of these can kill a beginner in much the same way a bad DMM can.

Officially older multimeters can be considered as a 'non-rated multimeter'.
Most meters produced before 1997 don't meet the standards.
Like the original Fluke 70-series.
Newer ones are mostly under-rated.

Isolation and proper (earth) grounding is a whole different story.

[Assafl]

All of these can kill a beginner in much the same way a bad DMM can.

Two wrongs don't make a right.

For the obvious snide remark - yes they do. One shock stops the heart, and the defibrillator one gets it pumping again.

Sorry - had to.

That said the laptop is probably worse:
1. It is in your lap. I have yet to stuff my DMM near my crotch once.
2. It is used much more than the DMM - for most. Hence the exposure to the risk is much higher.
3. Hopefully a DMM user can open his DMM and check the layout. In a brick - all you can do is trust china.
4. The percentage of DMM users aware of the risks is higher than the rate of brick users who do.

So bricks are substantially more dangerous. And like crap DMM makers, these also love fake or self certifications.

I say we shame them all.

[Electro Detective]

Blah blah blah... 

Once the plastic screw posts crack in MOST Flukes and other meters, you can kiss the BANG! containment CAT ratings goodbye   

Option 1:
A couple of duct/duck tape layers on the sides of the meter 'MAY' keep it together during a BANG!/POP/POW!
still a lot better than relying on tired flimsy cracked posts and deluded brand loyalty BS 

Option 2:
Rather than rely on 'coin toss' CAT ratings from any meter manufacturer, join some religion that can reserve you a spot in their afterlife program,
in case the hyped meter you are grasping goes nuke when performing a dumbass 'terminal' measurerment

Option 3: (My personal choice)
DO NOT TRUST ANY METER!    
Use what you have wisely, your family and friends have better things to do than visit your sad ass in hospital, rehab,  or crematorium/ditch site   

Option 4: Use FUSED LEADS, face shield, gloves, and dry wood holders for the leads,
especially if the day hasn't gone well or some scumbag stupervisor boss clown barks like a rabid dog    to hurry up and 'Just Do It!' 
(Option 4b: tell him or her to go **** themselves and stick the crappy job up their ***,
or hand them the CAT meter, and DARE them to measure the risky **** themselves  )

Option 5: Stick to Arduino stuff and battery checking

Option 6: Come on...if the 5 options above weren't enough
then don't buy a meter, and consider a hobby change to gardening or cooking instead   

[Fungus]

This thread is now 

(just like every other thread on this subject)

If you want garanteed safety then don't ever go near electricity. Or drive a car. Or go outside the house.

 

[Z80]

This thread is now 

(just like every other thread on this subject)

If you want garanteed safety then don't ever go near electricity. Or drive a car. Or go outside the house.

 

Well if it bores you so much then there are hundreds of other threads to go and troll in.

[Lightages]

Another relevant thread....
https://www.eevblog.com/forum/chat/my-first-dt830d-current-mode-spark/