Author Topic: Help! Total beginner- Just recieved my new UNI-T multimeter and I've killed it  (Read 22477 times)

0 Members and 1 Guest are viewing this topic.

Offline Simon

  • Global Moderator
  • *****
  • Posts: 13948
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
time to cool it maybe, if you think the discussion is such a waste of time simply stop replying.

Testing a batteries "amps" cannot be done, because you are shorting it, I think it's often done I did it too on my first meter, if you do it with a big battery yes at least your fuses will blow.

The fence wont deliver much power but that sort of voltage will jump through the air and parts made with sensitive CMOS technology will just be killed off by even a small current
https://www.simonselectronics.co.uk/shop
Varied stock of test instruments and components including EEVblog gear and Wurth Elektronik Books.
Also, if you want to get ripped off: https://www.ebay.co.uk/usr/simons_electronics?_trksid=p2047675.l2559
 

Offline Sorry State

  • Contributor
  • Posts: 10
The fence wont deliver much power
That's exactly what I had figured seeing as touching is 'the recommended use' of the fence.


but that sort of voltage will jump through the air

Now that I don't understand at all. I presumed the fuses would have protected any delicate CMOS technology. i don't understand how the fuses failed to protect the thing.
 

Offline allanw

  • Frequent Contributor
  • **
  • Posts: 343
    • Electronoblog
The fuses are only there to limit the current when measuring amps. There's nothing like an easily replacable fuse to protect the circuitry from high voltages.

The multimeter can probably be fixed if they won't take it for warranty. There's input protection circuitry that might be replacable.
 

Offline Strube09

  • Regular Contributor
  • *
  • Posts: 125
    • Blog
fuses are current limiting devices. We know that the fence will limit the current (As not to cook your cow leaning against it).

The voltage if great enough can arc across a blown fuse. Also they the voltage may have worked itself into a cmos IC that won't hand this kind of voltage.

To protect against voltage most inputs have MOV (metal oxide varistors) or some other voltage protection devices (Tyristors Zeners...). However even those have their limits.

 

Offline Bored@Work

  • Super Contributor
  • ***
  • Posts: 3932
  • Country: 00
It is about taking responsibility for your own actions and cutting your losses, instead of telling bullshit and blaming everyone except your own stupidity.

And I am disgusted by some commenters suggesting the criminal act of defrauding the seller by simply returning the instrument under warranty. No, that isn't clever or cool. It is plain and simple fraud.
I delete PMs unread. If you have something to say, say it in public.
For all else: Profile->[Modify Profile]Buddies/Ignore List->Edit Ignore List
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 13948
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
I forget the figure but a spark or arc will occur if there are "x" amount of volts per cm, the fuses are useless against high voltage and the voltage could jump from PCB track to PCB track until it got into something delicate and blew it. you don't need much current to blow a cmos IC, a few mA at 10'000 vots will certainly send it to IC heaven, but your fuse will not blow at a few mA as it is meant to blow at a little over the max the meter can take
https://www.simonselectronics.co.uk/shop
Varied stock of test instruments and components including EEVblog gear and Wurth Elektronik Books.
Also, if you want to get ripped off: https://www.ebay.co.uk/usr/simons_electronics?_trksid=p2047675.l2559
 

Offline Sorry State

  • Contributor
  • Posts: 10
To protect against voltage most inputs have MOV (metal oxide varistors) or some other voltage protection devices (Tyristors Zeners...).

They don't sound like (amateur) user replaceable parts?
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 13948
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
It is about taking responsibility for your own actions and cutting your losses, instead of telling bullshit and blaming everyone except your own stupidity.

And I am disgusted by some commenters suggesting the criminal act of defrauding the seller by simply returning the instrument under warranty. No, that isn't clever or cool. It is plain and simple fraud.

agreed, the warranty should not cover this as the instrument was used outside of it's specifications, lesson learnt ? good, don't do it again
https://www.simonselectronics.co.uk/shop
Varied stock of test instruments and components including EEVblog gear and Wurth Elektronik Books.
Also, if you want to get ripped off: https://www.ebay.co.uk/usr/simons_electronics?_trksid=p2047675.l2559
 

Offline Sorry State

  • Contributor
  • Posts: 10
It is about taking responsibility for your own actions and cutting your losses, instead of telling bullshit and blaming everyone except your own stupidity.

A couple of posts ago you were claiming my post was all lies, now you believe it? Haven't blamed anyone but myself.

Helpful as always. Cheers.
 

Offline Strube09

  • Regular Contributor
  • *
  • Posts: 125
    • Blog
To protect against voltage most inputs have MOV (metal oxide varistors) or some other voltage protection devices (Tyristors Zeners...).

They don't sound like (amateur) user replaceable parts?

These types of devices (provided they are not bad) are intended to automatically reset once the fault is cleared.  I am not sure the UNI has these on the inputs as they should have reset and your device would have powered back up... sound like it has gotten into the main controller of the unit.

I think you are probably out of luck.... but always keep it for parts you may need to replace the display on a future unit.
 

Offline Time

  • Frequent Contributor
  • **
  • Posts: 725
  • Country: us
Yep, 33,000 V/cm is the breakdown field strength of air at standard temperature and pressure.  So if you put 33,000 volts across a 1 cm gap it will breakdown.  Inside of a multimeter the field strengths between traces needed to breakdown are even less because the arcs can track along the surfaces, known as surface flashover.  Even further complicating the situation and raising the probability of breakdown are the points inside the meter where air, metal, and dielectric meet.  These points are called triple points and provide dense amounts of free electrons under HV excitation which can initiate a surface flashover event, making it even easier to break the device.

Gas discharge processes like surface flashover and volume discharge are somewhat chaotic and slow processes, so under pulsed excitation it takes larger field strengths for them to occur compared to a DC excitation.  This is why he probably doesn't see any visible carbon tracking (burns) from the failure because the pulses from the fence probably just blew up the first solid state device they ran into, internally.
-Time
 

Offline Sorry State

  • Contributor
  • Posts: 10
but always keep it for parts you may need to replace the display on a future unit.


No, I don't think I'm going to get another one. I've gone right off the idea of a multimeter. :(
 

Offline Kiriakos-GR

  • Super Contributor
  • ***
  • Banned!
  • Posts: 3525
  • Country: gr
  • User is banned.
    • Honda AX-1 rebuild
No, I don't think I'm going to get another one. I've gone right off the idea of a multimeter. :(

I think, that this is an good idea for now ...  If you ever get some training in the years to come ,
about becoming electrician or in electronics , at that time you will be more wise to handle such matters..

But I like to thank you , for a good reason .... suddenly you reminded to all of us, where we can find "True high voltage "  ,  because some they get confused with the Mains ( voltage on your wall plug) , and they considered it as master danger , for the multimeter's !!  

Take care ..   ;)  
And stay away of the electricity .. as all wise people do.  

 

« Last Edit: October 20, 2010, 08:19:21 pm by Kiriakos-GR »
 

Offline Strube09

  • Regular Contributor
  • *
  • Posts: 125
    • Blog
I disagree with Kiriakos. I think you should get a new meter and you should get back to experimenting. The only thing I would say is stay away from mains and other high voltage high amperage circuits until you get some better understanding.

I think it is important to never discourage curiosity. Where would this world be today if people just told you that unless you have training then you should just stay away?

I say if you are curious about electronics and electricity pick up a basic electronics book and a new meter and get to experimenting.

No, I don't think I'm going to get another one. I've gone right off the idea of a multimeter. :(

I think, that this is an good idea for now ...  If you ever get some training in the years to come ,
about becoming electrician or in electronics , at that time you will be more wise to handle such matters..

But I like to thank you , for a good reason .... suddenly you reminded to all of us, where we can find "True high voltage "  ,  because some they get confused with the Mains ( voltage on your wall plug) , and they considered it as master danger , for the multimeter's !!  

Take care ..   ;)  
And stay away of the electricity .. as all wise people do.  

 


 

Offline Nermash

  • Frequent Contributor
  • **
  • Posts: 256
My advice would be to get a new meter, stick with 9v battery and nothing above, and try to read up on the basics of voltage, current, and move on from there. And best advice I've read here before in someone's post: always use your best instrument first - your brain!
If you persist, soon you will know what happened to your meter and why it happened :)
Never stop experimenting, just use common sense question before you plug something in "Can it kill me, injure me or just cost me money?"
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 9214
  • Country: my
  • reassessing directives...
looking back at the original post, came to this line...
"Could an electric fence really kill a Cat III 1000v multimeter? I am so p*ssed off right now."

then who you are pissed off at? the uni-t? the fence? or yourself? if you are me, then i will choose pissed off at myself for not learning more before doing stuffs. ;) i believe you are not talking bullshit here, just expressing your experience (just as what i've experienced long ago). Cheers. ;)

so after you "painful scar' cool down, when you are ready to continue the quest of EE, you may get another DMM, and be prepared to study beforehand whats the DMM can do or not, how to measure amperage correctly etc. Dave's $100 shootout video alone will not do any good. It implied a sound knowledge at hand. You are quite luxurious though getting $100 DMM as you first and eventually killed it as most of us here did. Mine was a $3 AMM ;D So next time, maybe you'll get $300 DMM as your serious DMM ;), BUT... there is a big "BUT"... only when the time comes, NOT tommorow ;) (Mine currently is the Uni-T 71A, still in the $100 range, so i'm too a beginner! :D)

ps: it will be a nice experiment though to see how much high V the fence got. you may start getting the life-neutral/earth wires close together (using alligator clips cable perharps?). So if the figure is right, 10KV fence at 33KV/cm air dielectric. you should see an arc jump (spark) across wires through air at about distance 0.3cm (3mm). on the big scale, its the lightning you saw between clouds and earth. and also, probably thats what was happening in your dmm circuitry or even on the broken fuse. i've seen clearly this kind of nasty spark bypassing a resistor in electronics circuit. and i always ask my brothers/friends to earth their body before fiddling with my stuffs, i tell them, they can electrocute the circuit (static), not the other way around people usually understand it. so i think u should earth yourself after doing the fence experiment before doing any other EE related job.

well, mumble jumble here... got nothing to do at work ;)
« Last Edit: October 21, 2010, 12:38:49 am by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

  • Super Contributor
  • ***
  • Banned!
  • Posts: 3525
  • Country: gr
  • User is banned.
    • Honda AX-1 rebuild
I disagree with Kiriakos. I think you should get a new meter and you should get back to experimenting. The only thing I would say is stay away from mains and other high voltage high amperage circuits until you get some better understanding.

I think it is important to never discourage curiosity. Where would this world be today if people just told you that unless you have training then you should just stay away?

I say if you are curious about electronics and electricity pick up a basic electronics book and a new meter and get to experimenting.


No matter if you liked my advice or not ,  some things its a matter of age ..
One green tomato no matter how much red paint some one will use on it, its no good for salad ..

Ask first the age of the person that you give advices to ..

Thanks.
« Last Edit: October 21, 2010, 12:47:46 am by Kiriakos-GR »
 

Offline Sorry State

  • Contributor
  • Posts: 10
For what its worth I found out that the output voltage of the electric fence is 7,500 volts at approximately 2mA.

Anyway I'd like to thank you guys for helping me and providing feedback. While I have some rudimentary understanding of electronics  (I  specifically choose the 9v battery and the electric fence to experiment on as there was no danger whatsoever to me)  I had no idea that an agricultural electric fence had such a high voltage.

Thanks again.
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 9214
  • Country: my
  • reassessing directives...
7.5K x 2m = 15W. is it enuf to make us pain? seems small to me. i think if its like, 1000W (just for a moment) then it will feel something :D how much does it take to stop the heartbeat? or the safe margin for the body to take? just a thought.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 13208
  • Country: gb
  • 0999
The fence will also produce the power in pulses so the power will be much lower, probably 100s of mW.

I'd recommend buying a new meter and using it for low voltage, low energy sources (i.e. a small 9V battery, mains adaptor, not a car battery or the mains) but learn more (especially electrical safety) it before doing anything with it. By the way mains is not high voltage, it's low voltage. High voltage is generally any voltage high enough to cause significant arcing between conductors, typically anything above 600V or 1500VDC depending on which standards you're into, anything below that is low voltage.

Extra low voltage (ELV under 120VDC or 50VAC) is low risk and is unlikely to cause death although it will shock you, anything under 60VDC or 25VAC is generally considered harmless unless you're really wet, in which case no voltage is completely safe, although under 12VAC or 30VDC is unlikely to cause a lethal shock to even wet skin. Generally DC voltages are safer than mains frequency AC because the peak voltage is lower and the body responds differently to DC than AC. Higher frequency AC (above 20kHz or so) is generally safer than both DC and low frequency AC because it doesn't shock, although it can cause deep burns.

In informal use people often talk about low voltage as being on the lower end of ELV, typically below 60VDC or 30VAC and high voltage being anything above that but it's good to know the proper definitions. It's important to know that even really low voltages can be hazardous if the source has a low impedance (i.e. a car battery) because a large current can flow which can cause severe burns and batteries can explode. This is why I prefer the term low voltage, low energy source to denote sources of electricity which pose minimal risk.

I blew my first DVM too by trying to measure the output voltage of a DC fluorescent tube ballast without the tube connected. Fortunately the meter wasn't rendered totally useless and still worked on the DC settings. In the end I gave it to a friend who only wanted to use it to measure the DC voltage on
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 13948
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
7.5K x 2m = 15W. is it enuf to make us pain? seems small to me. i think if its like, 1000W (just for a moment) then it will feel something :D how much does it take to stop the heartbeat? or the safe margin for the body to take? just a thought.

it's not about power (watts) it's about the voltage and amperage. 7'500V will blow most IC's if applied to any pin even at uA it will just cause semiconductor junctions to break down. cmos chips use nA or uA for each transistor in the chip, so 2mA @ 7.5 KV will be plenty to blow the circuitry on any IC pin
https://www.simonselectronics.co.uk/shop
Varied stock of test instruments and components including EEVblog gear and Wurth Elektronik Books.
Also, if you want to get ripped off: https://www.ebay.co.uk/usr/simons_electronics?_trksid=p2047675.l2559
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 9214
  • Country: my
  • reassessing directives...
it's not about power (watts) it's about the voltage and amperage. 7'500V will blow most IC's if applied to any pin even at uA it will just cause semiconductor junctions to break down. cmos chips use nA or uA for each transistor in the chip, so 2mA @ 7.5 KV will be plenty to blow the circuitry on any IC pin
hehe! i was not so clear, sorry... i mean to human or animal, not the chip. for the chip, i know even our own static (high V with insignificant A) may cause it to damage. ;)
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

  • Super Contributor
  • ***
  • Banned!
  • Posts: 3525
  • Country: gr
  • User is banned.
    • Honda AX-1 rebuild
Well this multimeter will do  5KV ,  for 10KV use two multimeter s,  in series ..    :D   :D   :D


 

Offline saturation

  • Super Contributor
  • ***
  • Posts: 4788
  • Country: us
  • Doveryai, no proveryai
    • NIST
Some kV items sold in the consumer market:

piezo electric lighters or igniters for gas ovens

dog collar trainers

Tazer guns

electronic bug killers
Best Wishes,

 Saturation
 

Offline Time

  • Frequent Contributor
  • **
  • Posts: 725
  • Country: us
Inside a conventional microwave oven there is a 2 kV AC transformer.  Part this out, add a diode, add some HV caps, and finally a HV SCR and have fun "blowin' shit up". 

Be careful not to kill yourself.
-Time
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf