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#21
I'll take this in to concideration. And thanks for all the tips, too bad I don't have a boat!
I'll take this in to concideration. And thanks for all the tips, too bad I don't have a boat!
Ocek,
Your half way there!
You have a boat anchor.
Mellon Head, I'd like to point out, what you just described is a "double conversion" type UPS, as in it converts AC to DC, feed the DC to battery and then DC to AC inverter, thus: double conversion. This type is used by high end UPS, priced $400 and up. Efficiency numbers are around 80+%, very safe in terms of voltage supply to devices (double conversion design advantage). The electrical current characteristics will depend heavily on the inverter stage, if it uses a high quality clock generator, the sine wave output will be so good that it closely match what the power grid supplies.
On the other hand, an el cheapo ($50 - $200) UPS doesn't use this kind of circuitry, usually they rely on inverter/rectifier to charge battery and to supply electricity on the outputs when in battery mode, and a relay that switches between AC and Battery. The relay will switch to battery in few mili seconds in case of power failure. As for this type of UPS, it doesn't do any filtering by default. Unless the manufacturer includes an automatic voltage regulator module in the AC input stage, it doesn't have any filtering at all... In situations where the AC input stage got zapped by lightning, most of the time the surge will pass through to the output stage and hit whatever devices connected to the UPS.
As for multimeter use to check PC components, unless you know what you're doing - DO NOT USE IT. The risk is VERY HIGH for a novice user. Electric shock is very dangerous, if the shock didn't kill you, the after effect might...
zzz2496
What electric shock? If anything inside a computer creates a hazard, then nine volt transistor batteries are routinely killing people. Car batteries instantly cause death when touched.
Nothing inside the computer is dangerous when touched by a human. When using a meter, its probes are electrically insulated. When using the meter, then the very few here with electrical knowledge can reply.
I am appalled to the point of insult that so many people have so little electrical knowledge. zz2496 is completely correct. Those UPS claims about filtering, etc were bogus again due to no electrical knowledge.
The meter is the safest solution posted here. And results in a complete answer immediately. After so many posts, where has anyone posted what exists? No one.
Seriously more dangerous is swapping a power supply. Dangerous to the human. Dangerous to other computer hardware. Even that is tiny danger. Using a multimeter is even safer. And actually tells something useful. Swapping power supplies typically only reports 'maybes'. And does not report on any of the other power 'system' components. Yes, a supply is only one part of a power supply system.
What has happened? The OP will run scared. Entertain the emotions that hype fear of a meter. The majority do not represent reality. And demonstrate why the Silicon Valley cannot find enough electrically literate American. The meter is always the first tool used by an informed (first year) tech. Never disconnect even one wire because that can only increase danger to human and hardware. Knowledge in only one minute from a meter says what has or has not failed. Even 13 year olds to this - because meters are that dangerous.
Far more dangerous than measuring voltages inside a computer: connecting any appliance to an AC wall receptacle. Fear based in lies and myths easily keeps anyone from learning. OP has a perfect opportunity to learn so much – or to remain as electrically uninformed as so many others demonstrate. The least dangerous solution is a meter touching anything in the powered computer.
westom, in case where the electrical outlet's ground not providing good "ground", there are high possibility of getting an electric shock. In my country, where ground installations aren't mandatory, the computer case is conducting ~90 Volts (we use 220v system), that is quite high, enough to give you electric shock... I don't know the leak voltage in 110v system, but I don't want to risk anything. As for the probes it self, they are electrically insulated, that is correct, but at the hands of a novice, combined with bad ground and leak voltage, when his unprotected hands touched the case, it will induce quite a shock. If he went unconscious after the shock, the drop is the next risk... if he bump his head at the table's sharp corner, and bleed... Oh my... I don't want to talk about that....
I still stand by my opinion, open computer + AVO meter + novice = HUGE NO NO, the risk is TOO HIGH.
zzz2496
That is not what a power strip protector does. When typically grossly undersized (read joules in the specs), then its MOVs must disconnect as fast as possible from the surge. That leaves the appliance connected to AC mains and the surge.
Disconnect as fast as possible so that these scary pictures do not result:
http://www.hanford.gov/rl/?page=556&parent=554
http://www.ddxg.net/old/surge_protectors.htm
http://www.zerosurge.com/HTML/movs.html
http://tinyurl.com/3x73ol
entitled "Surge Protector Fires"
http://www3.cw56.com/news/articles/local/BO63312/
http://www.nmsu.edu/~safety/news/lesson-learned/surgeprotectorfire.htm
http://www.pennsburgfireco.com/fullstory.php?58339
A fire marshal even describes why the fire happens. Sometimes it does not disconnect from a surge fast enough.
No effective protector works by disconnecting. Disconnecting only promotes myths and sales. MOVs disconnect (ie thermal fuse) to avoid what every MOV manufacturer describes as completely unacceptable - see those scary pictures.
Effective MOV protectors remain functional and connected after every surge. Even after a direct lightning strike. Effective protectors even provide numbers because the only honest answer also has numbers. A direct lightning strike is 20,000 amps. So an effective 'whole house' protector is 50,000 amps or larger.
MOVs do not make energy disappear - another urban myth. Either an MOV makes a short (ie 'less than 10 foot') connection to earth. Or it must somehow absorb hundreds of thousands of joules. No MOV is protection. Effective MOVs connect hundreds of thousands of joules harmlessly to earth - or do nothing. Which is why power strip protectors sometimes earth a surge destructively via nearby appliances. Or create those scary pictures as seen by most every fire department.
Protection even from direct lightning strikes is routine - no matter how many time he replies with overt insults.
So if an MOV protects by disconnecting, then how does that millimeter disconnect stop what three miles of sky could not? Protection by disconnecting (or a UPS stopping a surge) is classic junk science reasoning.
Meanwhile, Ocek has a massive opportunity to learn how many myths and lies have been posted by others - if he obtains and uses a multimeter.
In which case, never use anything electric since touching its case will kill you. How often have you touched the refrigerator and been killed?
That danger only exists on the outside. No such danger exists inside. 1.8, 3.3, and 5 volts do not threaten anyone. What has much higher and more dangerous voltages? Telephone wire - 48 volts.
That danger from a missing ground only exists outside the chassis. Does not exist anywhere inside. Nothing exposed in an open computer chassis can cause a shock. Nothing. The most dangerous voltages are outside. Worse, you should know this.
Meter probes also are insulated. Even a screw driver creates a greater risk of electrical death - using your reasoning. So never use a screw driver? Amazing how many entertain fears. Anyone using a meter would learn how many posted myths without learning even the simplest concepts. You have just described why refrigerators are routinely killing people.
Even a telephone wire exposes five and eight times higher voltages. Even higher voltages on telephone wires are not dangerous. Please learn how electricity works before posting fears. If safety ground is defective, then touching your refrigerator killed you how many times? These fears are so ridiculous as to be insulting.
westom,
You are missing my point, it's not "using a screw driver will kill you", it's "opening a computer case without enough electrical knowledge might shock you". And there are deaths reports related to touching an ungrounded appliance here in my country, that is including but not limited to: CRT TVs, PCs, CRT PC Monitors, Refrigerators, and many others.
There's even this one stupid but true story, because the one that experience it is my friend, and I watched the whole thing right in front of my eyes. He lifts his PC up, he want to move it to another desk, he wants to clean it (the innards is filled with dust + nicotine residue + dog hairs + god knows what). When he started the lift, he wear his work shoe, rubber base. Once he moved, he feels that the shoe is not comfy, he just tossed the shoe aside, and his naked feet touched the granite floor. Instantly he got electric shock from the contacts of his bare hands to the unpainted parts of the computer case, as I look around, he didn't unplug the power cable, thus the shock... He tossed the computer to the floor, nearly destroying it... I had similar experience back in 386 days, I was around 12 years old back then, didn't realize that there's a "rogue" current running all over the case, touched an unpainted part of the case and got shocked...
Note: the computer is "OFF", it's just the power cable is plugged, power supply at "ON".
These days I have ground connection for all of my appliances, so the surprise shock is no more. Yet the memory is intact and I don't suggest novices to crack open a computer and start pointing AVO meter probes in the innards with the computer still plugged in and power supply at ON position. Just me and my experience.
zzz2496
I understood your point completely. But your electrical knowledge is too limited to understand that I get it.
For example, - erica647 - with simplest electrical knowledge, then you know the current through a body is determined by its voltage. E=IR. Why do car batteries, that output hundreds of thousands of milliamps, not electrocute anyone? You said current is deadly. Why do hundreds of thousands of milliamps not kill when only one milliamp can kill? Why do car batteries not electrocute anyone as you claim? Because voltage is so low. You never understood even that simplest concept? Voltage - as posted - is completely relevant.
Tens of times more deadly is using any appliance in a building with a defective safety ground. Where is a safest place to put your hand even if safety ground is defective? Inside a powered on computer.
Far more dangerous is that screw driver or by touching a refrigerator when safety grounds are unknown. Neither is very dangerous. And both are far more dangerous that using a multimeter or holding powered parts inside a computer.
Not knowing this defines zero electrical knowledge. Says eyes glaze over every time I post a number. What has five or ten times higher voltage? What (Attn: erica647) therefore can push five or tens times more current through the human body? Telephone wires. According to zzz2496 logic, never touch a telephone RJ-11 connector. According to his reasoning, that easily kills because a powered computer is so dangerous. According to zzz2496's every post, telephone wires must routinely electrocute home dwellers. Obvious once we apply numbers to his accusations.
A multimeter looks complex. Therefore it must be dangerous? Demonstrates why Silicon Valley companies complain so bitterly about technically illiterate young Americans. The so called computer literate kid is too often a complete technological lightweight. Not an exaggeration. Every junior high science student should have used a multimeter. Did you? Oscilloscopes were routinely used in high school science even 50 years ago. Obviously, you never did. Would not even know how to begin. Technical ignorance begets fear and myths.
Anyone who fears measuring voltages inside a computer is the technical illiteracy example cited by Silicon Valley companies. Perfect example of why 60% of new employees in the Silicon Valley are Indian and Chinese immigrants. Yes it is that scary. Any 12 years old kid can measure voltages anywhere in a computer. Even swapping a power supply is decades more dangerous. Hardly dangerous. But that many times more dangerous than using a multimeter. Please learn how electricity works before posting. Please stop scaring me about the future of mankind. Nobody should be that technically illiterate.