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How Do I Connect Mains To Oscilloscope Input?

12/17/2007 2:04 AM

Hello everyone.

I would like to hook my household mains up to my oscilloscope so that I can observe "the quality of my power" and see what happens when I turn on different devices. Devices like my air-conditioner and compact-florescent-bulbs (which seem to cause feedback on their phase), and possibly the output side of my UPS.

Obviously, I want to do this in such a way that I don't kill myself, damage my scope, start a fire, etc.

So I'm looking for suggestions on how to build a cable for this that can be disconnected and reconnected as desired. I'm particularly interested in correct cable wire gauge, fuses, connectors, whatever should be used.

I live in the United States, so this will be connected to 120 VAC @ 60 Hz on a 10 to 20 Amp circuit.

My oscilloscope is a GOS-622G (all analog). The 2 inputs are BNC connectors labeled "CAT. II 400Vpk MAX" (Volts Peak) with the outsides marked ground and a separate ground lug and 100Vpk EXT for selectable trigger.

I should be able to connect my little probes directly to the mains, right?

It's been about 10 years since my electronics class, but as I recall there should be near infinite resistance across the signal/ground , so I'm thinking about taking a lamp or extension cord, figuring out the polarity, connecting/soldering neutral to the outside of a salvaged BNC connector and the "hot" to the inside. and wrapping the whole thing in a heat-shrink insulator. No fuse or switch. Initial tests will be using a GFI outlet.

Does this sound OK, or do you have any better ideas?

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#1

Re: How do I connect mains to oscilloscope input?

12/17/2007 2:33 AM

Ok, you can connect your probe to mains line directly, only pay attation to attanuate the knob on panel (response to the probe input) to maximum. and coarse adjustor to maximum.(1/3) , so that you can get 1/150 or 1/180 attanuation. and time base at 2ms or 1ms to keep waveshape stability.

the operation is very easy. only take careful. do touch bare wire by your hand directly.

good luck.

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#2
In reply to #1

Re: How do I connect mains to oscilloscope input?

12/17/2007 2:41 AM

at AC step.

neednt take account of polarity.

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#11
In reply to #1

Re: How do I connect mains to oscilloscope input?

12/18/2007 2:35 AM

cnpower,

sorry, but your reply is both negligent and dangerous, hardly befitting of a 'guru'.

cheers

RF_guy

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#23
In reply to #11

Re: How do I connect mains to oscilloscope input?

12/18/2007 7:45 AM

RF guy, if you are going to flame somebody I would expect some reasons for why the information is wrong and what the correct information is. Anything less is just an insult and not part of the purpose of this board.

Personally I don't see anything wrong with the approach of simply probing the AC outlet. Electricians do it all the time with a DVM or test light. What, pray tell, are you banging on about?

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#24
In reply to #23

Re: How do I connect mains to oscilloscope input?

12/18/2007 8:02 AM

What I'm banging on about, ca1ico (great handle, btw!), is that 'just probe the outlet' is a dangerous thing to tell someone, when it's clear that they're not really sure what they're about.

A good way to torch the scope and possibly the user (see e.g. post #20, even if he has trouble with English syntax, put it quite rightly, "ya turn the probe into a very bright/hot fuse"

Simply plugging in & turning on a 'scope then plugging the probe directly into the mains without knowing what voltage differences/current flows are present could be very dangerous for both equipment & persons. For more info read my post. I rest my case.

RF_G

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#27
In reply to #24

Re: How do I connect mains to oscilloscope input?

12/18/2007 8:21 AM

Dead right!!

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#40
In reply to #24

Re: How do I connect mains to oscilloscope input?

12/18/2007 10:55 PM

First of all, you seem not to read the first thread, he said the power rate is about 120v USA mainline electric power.

If you know this point, you will understand why we could suggest the poster to do in that way.

None here will suggest a man to test a unknown power with an instrument.

Its good for anyone to do test prudently, but test needs science data.

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#51
In reply to #40

Re: How do I connect mains to oscilloscope input?

12/20/2007 11:25 PM

Set Cab. at half positon and input attenuator at x20, so that you get about 1.5x20 = 30 attenuation. you can view the waveform of 4 grid scale. very clear.

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#26
In reply to #23

Re: How do I connect mains to oscilloscope input?

12/18/2007 8:20 AM

He won't find out much with the approach he is planning and others have mentioned using a transformer, which will tend to cut down on the size of the spikes that he may be getting......also not a good idea except that is safer....

End result is, he should not waste his time in the manner he is planning to do as it will probably bring him nothing but woe.....sorry!!

Happy Christmas.

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#29
In reply to #26

Re: How do I connect mains to oscilloscope input?

12/18/2007 9:40 AM

which will tend to cut down on the size of the spikes that he may be getting..

Not from my experience....spikes go through just about anything... It's hells own job to supress the buggers....

Del

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#33
In reply to #29

Re: How do I connect mains to oscilloscope input?

12/18/2007 2:07 PM

It depends on the speed of the pulse really....of course huge pulses always get through....anything!

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#38
In reply to #11

Re: How do I connect mains to oscilloscope input?

12/18/2007 10:38 PM

It might not be a good idea for those who need often to test the mainpower, but occationally can be used to do a test wave shape.

My workers is used to do it when they find the power quality is bad, becasue our neiboor institution often run their mid frequency oven for melting alloy experience. when the oven works, the main power will has seriously interference and you can saw the spikes produced from SCR control angle. the oven is high power.

When they do it, I told them dont touch any part of the oscillascope and insulate from eath very well. no problem.

The main here is 220V or 310vpp, the probe insulation is up to 600v and input of the set will be at least 600 or up to 1o00v. If you comprehend the rate. why do you object?

Hve you ever seen super high voltage working with power?

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#3

Re: How do I connect mains to oscilloscope input?

12/17/2007 2:57 AM

I'd strongly suggest you connect the probe via an isolating transformer.

It only needs to be a titchy one, costing a couple of $, but it could save your nerves, your 'scope, and maybe your life.

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#93
In reply to #3

Re: How do I connect mains to oscilloscope input?

12/23/2007 11:21 AM

Floating Oscilloscope Measurements ... And Operator Protection

Safety Engineering Principles

Safety - A Shared Responsibility

Table 1. Methods of Making "Floating" Measurements Using Tektronix Instrumentation

Safety Engineering Principles

Tektronix has adopted many safety principles in the design of their products. Of particular concern to making electrical and electronic measurements are these principles:

When the instrument is used properly, accessible parts shall not become hazardously live, even in the event of the single worst-case fault.

Electronic devices (those devices employing conduction in a vacuum, gas, or semiconductor) shall not be relied upon for providing operator protection from electric shock.

Products should not develop insidious hazards during proper operation (an insidious hazard is a hazard which can develop in a way as to be well established before becoming apparent).

The operator shall not need to defeat a protective system to make the measurement.

Safety - A Shared Responsibility

The operator and employer share in the responsibility of meeting these principles - through proper operation and measurement techniques.

WARNING

Never attempt to defeat the protective grounding system of your oscilloscope by using an isolation transformer (top) or disconnecting the ground connector on the power plug (bottom). Failure to follow safety warnings can result in serious injury or loss of life.

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#94
In reply to #93

Re: How do I connect mains to oscilloscope input?

12/23/2007 12:10 PM

1) The guy does not have a Tektronix 'scope, it's an Instek.

2) Why are you having a go at me? I've bitten my tongue here since my post #49 12/21/2007 1:04 AM - and, by the way, I still don't know who you were upset about, or why.

3) From your post #80, I assume you've got a pretty big axe to grind. Please go and grind it somewhere else.

4) Please ignore my signature.

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#96
In reply to #94

Re: How do I connect mains to oscilloscope input?

12/23/2007 1:03 PM

It's not a go or otherwise; This is from a website; they are not my words!

Sir, I am not snapping at you or anyone; It is only an addendum to your advice. Besides, when is a reply not a reply?

Damned, I thought I had a short fuse! What's with all the Bias and Prejudice? Am I not a member of this "forum"?

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#97
In reply to #96

Re: How do I connect mains to oscilloscope input?

12/23/2007 3:21 PM

Ok, pax vobiscum.

If I've misinterpreted your words or intentions, I am sorry.

Please be careful, though, when including verbatim from other websites without stating what you are doing. e.g. your post #80 looked very much like a plug for your own products ("Although part of our regular tutorial series,..." "... we have had ..." and so on). Be careful that you don't tar yourself with someone else's brush.

Also, within your extract (post #93) was a statement re. isolation transformers which seemed to be a direct refutation of my suggestion.

Wishing you a Happy Christmas and a Healthy and Prosperous New Year,

John

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#98
In reply to #97

Re: How do I connect mains to oscilloscope input?

12/23/2007 4:12 PM

OK and "pax vobiscum" to you too!

Will do!

MERRY CHRISTMAS and a Happy New Year to you and your loved ones...

PS. www.bioteknica.com was my only plug; the rest are from websites in Google.

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#95
In reply to #93

Re: How do I connect mains to oscilloscope input?

12/23/2007 12:32 PM

On re-reading:

If this

"Never attempt to defeat the protective grounding system of your oscilloscope by using an isolation transformer"

is your problem with my post #3, note that I said

"...connect the probe via an isolating transformer...".

Please explain how that could present a hazard.

On second thoughts, don't bother.

Still ignore my signature.

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#4

Re: How do I connect mains to oscilloscope input?

12/17/2007 3:13 AM

It might be more prudent for you to connect probe hook to only one fire wire of main line. the wave shape can also display on the screen.

Most people and textbook suggest to use a isolate transformer, but in fact, the power inuput of oscilloscope ususally has a insolate ppwer transformer. this tme you dont touch any part of the set and keep the set from earth.

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#5

Re: How do I connect mains to oscilloscope input?

12/17/2007 5:07 AM

<...so that I can observe "the quality of my power" and see what happens when I turn on different devices...>

The oscilloscope will only indicate the shape of the AC voltage waveform at the point of measurement. It will not give information about power factor with just one input.

Fusing the voltage input to the lowest practical minimum (20mA?) might prove attractive so as not to be unpopular with various insurance companies.

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#6

Re: How do I connect mains to oscilloscope input?

12/17/2007 8:32 AM

As the others have already said, you can often just hook the probe to the live (check scope spec' first)...but this does have some risks.

The question is really what sre you looking for?

Voltage fluctuations (relatively slow)?

Spikes? (relatively fast)

A small step down transformer (just check primary and secondary are isolated...) Will show most transients perfectly well at a nice safe voltage. It will also show the slower fluctuations, but obviously scaled down... e.g a 240-24v transformer would give a nice convenient 10:1 ....

A DVM is probably best for actual AC volts values.

You could also simply AC couple for viwing spikes...

Triggering and observing the transients is the hardest bit unless you have a storage scope.

Del

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#8
In reply to #6

Re: How do I connect mains to oscilloscope input?

12/17/2007 10:00 PM

Mainly I want to see the waveform, see if it's really pure, and see how it's affected by various devices in my home: motors, florescent lights, plasma globe, heating elements... So MOSTLY I guess what I'm interested in are the spikes.

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#14
In reply to #8

Re: How do I connect mains to oscilloscope input?

12/18/2007 4:22 AM

<Mainly I want to see the waveform, see if it's really pure>

Why?

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#15
In reply to #14

Re: How do I connect mains to oscilloscope input?

12/18/2007 4:39 AM

Slack,

pardon me, but are you serious? (sometimes your answers are tongue-in-cheek but it's not always clear, it leads to misunderstandings..)

While he may not be able to discern PF influence looking at only one source, distortion of the AC waveform by the lights or the UPS will certainly indicate there is a problem..

RF_g

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#19
In reply to #14

Re: How do I connect mains to oscilloscope input?

12/18/2007 6:27 AM

Because he's interested, he said. However, as the saying goes 'curiousity killed the cat'.

Del was perfectly right in every details.

Just do what he said!

Down scale the voltage so you won't have danger lurking at you and if you do not have a CRO probe with attenuator switch on most likely the wave form goes beyond the size of your gaticule.

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#7

Re: How Do I Connect Mains To Oscilloscope Input?

12/17/2007 12:59 PM

You ought to be able to go down to Radio Shack and get the proper probes with BNC outputs to do this.

Do you really want to look at the mains? You can hook to each cirucuit and check them individually.

Why do you think you are getting feed back on their phase from the AC?

I did a thermal survey of my electrical system once and found that one of the leads to the meter box had come loose and was slowly frying the connection. This was causing all sorts of funky power glitches in the house. Seem that even if your house is copper wired, it is not unusual for the electrical service from your transformer to your meter to be aluminum, so the connection in the meter box needs checking occasionally to make sure it has not loosened up.

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#9
In reply to #7

Re: How Do I Connect Mains To Oscilloscope Input?

12/17/2007 11:36 PM

:: You can hook to each circuit and check them individually.

That's what I plan on doing. I may try to get 1 channel on each phase so I can display them both at the same time and see the offset. (Is it pi?)

:: Why do you think you are getting feed back on their phase from the AC?

Not from the AC.

I have a bathroom vanity with 4 compact fluorescent bulbs in it. On several occasions, the lights have been on for a while and then flickered and went out. Flipping the light switch for a minute brought them back on.

I have determined that when they go out, other circuits that use that phase of my breaker box stop working. Electrical outlets stopped supplying power (voltage drops), and the stove and window air-conditioners (which use both phases for 240V (120+120)) stopped working.

I read at one point that electric companies are having problems because the CFLs are causing feedback.

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#39
In reply to #9

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 10:41 PM

Cutter,

As the type of scope you will be using wasn't stated, I would recommend that you be careful as most older, non-isolated oscilliscopes share the reference/shield between the two channel probes, the case, and the AC power supply lead/cord ground conductor.

If you should error and touch or attach the probes incorrectly, you will effectively short-circuit the two power conductors being probed for sampling and the result could be fatal. If your scope is of the older type do not use the reference/shield leads and instead use capacitive-coupling lead(s) or an isolation transformer as previously suggested.

Also be aware that harmonics and high frequency disturbances occur at different frequencies than the AC power and it will be necessary to change the timebase and trigger settings in order to capture some of the dynamics happening in your system.

A Dranitz meter would be a better way to look for system disturbances and/or you could use a high-speed power recorder specifically designed for this use. Both can be rented for a reasonable fee.

Good luck and stay safe.

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#41
In reply to #9

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 11:24 PM

You must be making a mistake.

at the first, the term of cfl caused feedback is not correct. as a saving energy lamp, cfl has a high effeciency than incandicent lamp. it has ressamble constuction as compact fluorescent bulbs. when they are flickering, it must be has something wrong with their inner circuits.

the circuit is a hf power supply. when they go wrong the lamp will flicher. you have to check out at first when you buy, to see if its suit to 120v or 220v main power. if not, change them to suit to your power.

These circuit has large range fo voltage chang , no problem for _+20% ripple.

Second check your all appliance power , to see if they are over your rate in room. theis will cause trouble.

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#42
In reply to #41

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 11:32 PM

Beside, I even wonder why you install so much compact fluorescent bulbs in your bathroom?

How much size si it? very large enough 40M^2?

if they cannt get a good touch, there will be also problem. becuase of vapor from pool

ah, so many people take care of it.

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#10

Re: How Do I Connect Mains To Oscilloscope Input?

12/17/2007 11:57 PM

Forgive me if this too basic but I would like to point out some safety factors if you intend to work on live circuits.

One is, stand on a piece of wood and don't touch anything that could be grounded.

Two, never stick anything conductive between live 240 volt legs. It can, and sometimes does, arc over. This arc can burn you horribly.

Three, never bond the neutral and ground anywhere than at the service entrance. It can burn your house down.

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#75
In reply to #10

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 5:04 AM

Ref Post 10 Mr.Skelley

Three, never bond the neutral and ground anywhere than at the service entrance. It can burn your house down.

The above is a quote from your posting.

If neutral and ground are are connected together at the service entrance, why can't one do it elsewhere? I know that it should not be done. I never do it. But I am not able to correctly explain the consequences. Can you help me with an explanation?

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#76
In reply to #75

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 7:26 AM

Do you know anything about electricity? Alternating current? Grounding?

Seriously: What is meant by phase ('hot'), 'neutral' and 'ground'...?

If you think about it, Mr. Skelley's answer is obvious.

Merry Christmas and a happy, healthy New Year

Regards

RF_G

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#79
In reply to #75

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 9:20 AM

Try the following links, they explain the problem better than I can:-

http://www.smartpowersystems.com/New/PDF/Articles/mw%20ng%20article.pdf

Neutral-to-GroundConnections

In the second link, well down the page, it states the following:-

What are the dangers associated with improper neutral-to-case connections [250.6]?

Improper neutral-to-case connections can create a fire hazard, electric shock and electrocution, improper operation of protection devices, and power quality issues for sensitive electronic equipment. Particularly when the neutral is open or it has a high impedance path.

I hope that this answers your question fully......

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#12

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 3:52 AM

Oscilloscopes which are powered from the mains have their metal case connected to the ground . One of the two wires of the probe(earth or common wire) also is connected to the earth through the case of the oscilloscope. In such a system, there is a possibility that during the measurements you may make a direct inadvertent contact with the common point or or through a low impedance path. To avoid all these problems one can use an isolation transformer to power the oscilloscope. But in this case case one cannot use to advantage the parasite filtering circuit of the oscilloscope which is connected to the earth point. Why not consult with TEKTRONIX ?

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#28
In reply to #12

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 9:01 AM

It's not a Tek scope

http://www.tequipment.net/InstekGOS622G.html

cheers

RF_Guy

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#13

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 3:58 AM

Greetings, Cutter-sedder, everyone,

it sounds like you're more or less aware of what you're doing, but some of the posts leave a lot unsaid. It's always difficult to ascertain what can be assumed as understood...

BTW, to focus minds, the lamp-cord pigtail you're talking about making is known as a 'widow-maker', at least in New England ;-)
I would recommend not using it, see below for why.

I disagree strongly with cnpower's post, esp. beginning with "Ok, you can connect your probe to mains line directly" NO!! or at least, not until you've checked some things!

As is mentioned or alluded to in some of the posts, we don't know what's lurking in your house wiring. These unknowns can be deadly for Scope and Operator.

Based on your description of your scope, you can probably connect it, but before you proceed, first perform a couple of simple measurements with a multimeter (these may also help in diagnosing your problem!):

1. I assume you have grounded outlets? Measure the voltage between phase and neutral (i.e. the 2 'power' pins/slots) and between each of those and the ground. You should see e.g. 120V mains voltage between the power pins, and only a volt or a couple of volts between the neutral side and ground. Larger voltages between neutral and ground should be regarded with suspicion and extreme caution. Do this for several outlets in several rooms / on several floors...just to see if any of them are swapped (?!) If you're really suspicious, pop a couple of cover plates to see if there IS a ground connection...I've seen plenty that weren't even hooked up...

2. next, plug in the scope and turn it on. Using the DVM, *CAREFULLY* measure the voltage between the scope chassis, the outside SLEEVE of the BNC inputs (i.e. not the center pin, at least not yet), and the GROUND and NEUTRAL of the outlets you wish to measure. This will establish whether you have mains voltage across places you don't expect it/want it. Next, set the multimeter to the highest current rating (usually 10 Amperes) and measure between the neutral and ground on the outlet to the scope chassis and BNC sleeve...hopefully you'll see '000'. Gradually decrease the current setting on the meter until you're at the lowest level...hopefully you should arrive at a point where there are only micro- or at the most a milliamp or two flowing.
If there are large currents or voltages found during these measurements, there is probably something seriously wrong with either the house wiring or the way the (older?) scope handles power supply & isolation. Then I'd stop and get that sorted (maybe get some more experienced help on site) But if everything is cool at this point, proceed.

3. Going back to your set-up (plug/lamp cord/BNC connector/shrink-tubing) - I've made lots of set-ups, all the way up to kilovolts (100's), but I don't like this one because of the implied ground of the BNC outer sleeve combined with the ambiguity of plug/outlet ground (i.e. if there's a swap somewhere the BNC connector is hot on the outside!). So what to do? The point is, we want to avoid you grounding either phase or a mis-wired neutral with your scope (or you!).

The bottom line is: check the connection between scope and outlet FIRST with the meter, to make sure there aren't mains voltages or currents flowing between things which you would assume to be at or near ground.

Regarding a set-up, if you want to make up a mega-safe set-up, take your plug and solder three resistors to it, in series, between the sides of the plug:

O---100k---TP---1 Meg---TP---100k---O

'O' = plug sides (outlet)

You measure across the 1 Megohm resistor, connecting the scope to the 'TP's (test points).

The 100k resistors prevent you from drawing more than a milliamp or two of current off the mains, but you'll have about 100V across the 1 Megohm. (make sure your scope can take that! - if it can't, adjust the 1 Megohm downward to result in a lower voltage, say to 250-500k)

One last, old-timer tip: when poking about mains voltages (or e.g. if you decide to pop the cover off your main fuse panel to see if the neutral is indeed tied to ground), an OLD electrician once told me: keep one hand behind you, gripping your belt.

Prevents you getting your hands across voltage - a current flowing from one hand to the other = a current flowing across the heart, which is one of the typical ways people get electrocuted. Note that I say he was an OLD electrician :-)) Also, as one poster said, avoid the obvious stuff, don't be doing this standing in bare feet in a puddle of water with the cord from the hair-dryer and the toaster lying in the same puddle etc. And of course it helps to have a buddy with you (without his or her hands on the same circuit!)..

Good luck, and post again if you find anything strange or need more help, there is plenty of good advice on this site.

Regards,

RF_Guy

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#43
In reply to #13

Re: How Do I Connect Mains To Oscilloscope Input?

12/19/2007 12:01 AM

You neednt to write " strongly object"

your words are so long, only electrician can understand some terms in it. Do you iknow its also dangerous when you test mainline with a multimeter?

Why dont you point out, you hve to pay attation to test voltage witha multimete when you touch line wire. be sure to set it step at AC voltage! if you set to other step like resistor or current strp, your meter will be burned! and if you set to DC step to measure AC, it will give a wrogn reading!

Do you know 500V insulation at least for low voltage appliance? Hve you ever read 120V in the first thread?

Pardon me. I guess you must be a school teacher or from some institution, and hvent ever visited factory or worked on suit.

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#50
In reply to #43

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 11:10 PM

correct:

why dont you point out, you should pay attention to do the test when you connect mains wire with multimeter. and be sure to set the multimeter at max AC step! keep resistor or current step from it. otherwise, it will either be burned your meter or be risk to your body.

if you set to DC step, it will cause a wrong reading.

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#58
In reply to #50

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 1:57 AM

...as usual, being silly again with respect to safety........!!!!

Sarcasm does not become you, good specific points on safety will

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#16

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 4:56 AM

not a good idea, also you would only see "instant" readings of spikes.

You can rent or buy a small piece of equipment (Voltage monitor) that stays connected for several days (if you wish) to your mains supply via a standard plug and it will log the voltage in your house and the numbers of spikes of varying sizes with a date and a time.....continuously.

You can usually download the statistics to a PC for study later with the modern versions.....older ones use a paper tape.....

This is the only way to know if your mains is good or not and a lot less dangerous than what you are proposing......

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#18
In reply to #16

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 5:49 AM

Hey Andy,

agreed...but Poster asked how to do a measurement.

Might give him enough info to go on with a power-line monitor.

I wonder whether he will see spikes (you mean, from the 'saver flourescnets?) or a gawd-awful 'not-sine-wave' caused by the UPS hogging current..?

Grüss

RF_G

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#25
In reply to #18

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 8:16 AM

I do not think that he really knows what he is doing here and it is not the best way to analyse whats going on with the house electrics. If he has problems, then he needs to do it right.....as the old saying goes "If I was to drive to London, I wouldn't want to start from here.....!

I used to have to do this work when preparing for large computer installs at customers with heavy electrical equipment!!!

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#17

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 5:30 AM

For safety sake I suggest you use a current probe.

Check out Fluke.

Scoba1

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#20

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 6:27 AM

depending on ya skill level with AC, the first thing is where do ya connect the O-Scope probe return line to. Reason why, most scopes AC pwr line source has a return(ac grd) which if ya connect the probe wrong to the AC test point ya turn the probe into a very bright/hot fuse. maybe ya should use an Isolation Xtramsf in-line with the scope ac pwr source or ya could just remove the scope ac grd with a special adaptor attached. tho ya still have to understand how to attached the probe to the AC test side, for while ya probing and if ya connect with hot side to probe return and ya touch the metal side of the o-scope with one hand and come in contact with a AC grd/return with any parts of ya body, it could be somewhat harmful for ya.

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#22
In reply to #20

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 6:45 AM

lurn 2 rit rit

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#34
In reply to #22

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 5:08 PM

LOL, I forgot to sign in the first time, tho have seen what a tech did with a probe once trying to measure ac, it did turn into a fuse.

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#21

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 6:33 AM

An excellent piece of equipment is The Fluke VR101S a lot safer and more detail. I use them in various places through out our factory.

Set up, plug in, download, and analyze

Homes, offices, hospitals, and factories depend on electronic devices. And electronic devices depend on good power quality. The Fluke VR101S is the perfect system for catching sags, swells, transients, outages and frequency variations on line voltage at receptacles, where the most sensitive loads are connected.

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#30

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 9:48 AM

AS your oscilloscope is grid powered, the best way to stay out of trouble when measuring grid AC is to permanently power your oscilloscope through an insulating transformer (110V to 110V) which provides galvanic separation.

The second way is what Del suggested: do your measurements through a step-down transformer which again, will provide galvanic separation.

Thirdly, do some reading on what you actually can do with your oscilloscope in terms of bandwidth, time base, probes calibration, etc. For that, you can follow the links on:

http://www.educypedia.be/electronics/measurementosc.htm

Oscilloscope measurements are very tricky and can lead to erroneous conclusions if you don't know exactly how to trim your probes and what are the limitations of your instrument.

If you are particularly interested in AC power measurements, for $250-300 you can buy an AC datalogger that can record and lately download graphs on your computer showing all transients, harmonics, spikes, power factor, etc. when connecting/disconnecting various loads. Let me know if you need a link for that.

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#31
In reply to #30

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 9:52 AM

Sorry, I forgot to login when sending post 30.

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#32

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 11:30 AM

As has been elaborated on you can possibly connect your oscilloscope to the mains even if it is a bit dangerous and time consuming to be relatively safe at doing so. However, the problem you are describing sounds a lot like what is called a brown out around here. There ain't a darn thing you can do about it if it is. And, unless you are planning on spending a lot of time staring at your scope, I fail to see any benefit of attaching it to your mains unless you are just awfully lucky at being there when the voltage dips. Have you thought about a commercial grade UPS for your electronics?

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#44
In reply to #32

Re: How Do I Connect Mains To Oscilloscope Input?

12/19/2007 12:21 AM

I have a UPS for my computer and have never had any problems.

The CFL thing is really weird. It's not a brown out. As soon as I flipped the light switch, everything started working again. It's happened that way more than once.

Mainly, I just want to SEE the waveform. Everybody says it's a sine wave, but I want to see it for myself, just for the sake of seeing it... I know that sounds a bit silly, but part of science is exploring things for yourself.

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#45
In reply to #44

Re: How Do I Connect Mains To Oscilloscope Input?

12/19/2007 8:46 AM

Then my advice would be go 4 it! I have observed the main voltage on a scope before and indeed it was a sine wave with some high frequency noise. Not terribly remarkable but I guess it is worth a look see. I would suggest replacing your ballast on your flourescent to see if the problem goes away. You may have a potential fire hazard there. It may also be a combination of things. I would probably be doing a lot of continuity checks, paying particular attention to resistances that seem abnormal. Poor connections can be a bear to trace down sometimes.

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#46
In reply to #45

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 2:10 AM

Poor connections when loaded get hot and are a constant cause of house fires.

Today, you can buy for relatively small money "Temperature Sniffers" which show differences of temperature of less than a degree. Some use a Multicolor LED and some of the expensive ones use a color LCD screen to display the results.

Using these instruments, a lot of electrical connections can be quickly scanned for heat problems very quickly - a house fire costs more than the $100 for the cheaper ones and they can also be used to find "cold Bridges" in house walls or badly fitting windows, showing a quick amortization for heating costs alone......

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#35

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 5:24 PM

There are cheap all plastic lcd screen 'scopes,just as safe as a multimeter and similarly constructed.Make sure to use an all insulated bnc connector,and an insulated croc clip at the probe end.

I use one for up to 400v with suitable dividing probes,although commercial 400v probes are expensive,120v should be ok with an ordinary divide by ten probe.

I really advise against using a metal case 'scope on mains,you never know what the probe 'earth' is going to encounter and unless the 'scope earth is really well connected the whole case could become 'live'.

Dont forget that earth and neutral are not the same,especially as you seem to have a disfunctional supply, so connecting the 'earth' alligator clip of the probe to the neutral could cause a few amps to flow,blasting the usually fragile probe leads.My early attempts with an old tele 'scope resulted in a melted earth clip and a few good belts as a warning.

I have in desperation operated a scope on a UPS unconnected to the mains,but only to test dodgy low voltage power supplies with weird connections to earth,but never to check mains voltages deliberately,as I am afraid I would have an absent minded twiddle at the sync and fry.

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#36

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 7:46 PM

There are several ways to do this; you can tap directly, which I don't recommend; you can use a Donut or an isolation Xformer. Follow the advice of the other contributors on safety and attenuation because I haven't done this type of work in a long while.

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#37

Re: How Do I Connect Mains To Oscilloscope Input?

12/18/2007 8:02 PM

I forgot to mention that a Good variable Xformer works well also! And on the subject of downplaying or insulting the other person because of Race, Color, Origin or level of education; we should project professionalism and etiquette in every answer and response that we give and with respect to this forum; this is not your neighborhood bar!

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#47
In reply to #37

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 5:30 PM

You mention variable transformers alongside isolation transformers and I suspect you may have forgotten that usually variable transformers 'Variacs' etc are autotransformers, and have no isolation between input and output,although their use to feed a double wound transformer would give isolation and variable input voltage to the 'scope.

Please warn our less informed correspondents not to use a variable transformer as a means of isolation.

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#48
In reply to #47

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 5:51 PM

In case you have been mislead; this is an engineers forum. For Sesame Street, Disney and all others, please get permission from your mommy and daddy fisrt and then log-on! This is an Engineers Forum, all information is for trained and experienced personnel!

If in doubt...READ THE WEBSITE TITLE!!!!!!!!!!!!!!

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#57
In reply to #48

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 1:54 AM

That might be a "let out" for you, but NOT for the majority of CR4 posters.....

There are a lot of what I would term "Incomplete Professionals" and "downright beginners", therefore safety must always always be paramount when we answer or give suggestions.

Most CR4 people do it as a matter of course and I am not going to argue the point with you but remember you may feel a little bit "miffed" if I or another "Real" CR4 professional adds some important safety points to anything that you write.......it then looks as though you did not fully understand the important points - and that WILL happen.....I am sure that would not be seen as particularly helpful by yourself. but I personally feel that when I forget something like that and another adds it, that is teamwork! But many do not, they take it as critic of their knowledge, then I say they are being childish!!

But it is always meant in a helpful and safe way. no matter how it is taken.....

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#56
In reply to #47

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 1:45 AM

Really well put!

Many, even "so called" professionals forget this important and possibly "deadly" point.

I got slagged by another Blogger recently when i told him this and that he forgot to mention it, in a different CR4 blog......!!!

Safety is (or should be!) paramount here as we never know the knowledge level of the "reader"......

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#49
In reply to #37

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 8:04 PM

Would you please either reply to a post, or state in your post to whom you are directing your comments. As far as I can determine, you are firing off at oldeng, but I'm not sure if, or why.

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#52
In reply to #49

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 11:25 PM

Would you please either reply to a post, or state in your post to whom you are directing your comments. As far as I can determine, you are firing off at ronald, but I'm not sure if, or why.

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#53
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Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 11:28 PM

Would you please either reply to a post, or state in your post to whom you are directing your comments. As far as I can determine, you are firing off at Guest, but I'm not sure if, or why.

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#59
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Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 1:57 AM

What are you talking about? so many repeat? Im curious.

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#61
In reply to #59

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:03 AM

If you follow the Blog carefully, it will become completely clear. If you still do not follow it, let me know and I will document it for from Post # to Post #.

It could have been a bit clearer I do agree with you on that point!!

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#66
In reply to #61

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:51 AM

Thank you at the same. I have neither time nor skill to read the blog you metioned.

forget it.

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#68
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Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:02 AM

I was just trying to be of service.

Its already forgotten!!!

I must go now, I will reply later to anything further.....have a great day.

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#72
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Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:43 AM

see u next week.

I can come back next week.

warmly welcome to point out my mistake. I shall thank u.

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#54
In reply to #49

Re: How Do I Connect Mains To Oscilloscope Input?

12/20/2007 11:32 PM

You see what you have started?

Please refrain from this type of explosive outburst, it does not contribute anything positive to this forum!

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#60
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Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:00 AM

It will if you try and set some good examples with regard to both reply and safety!

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#55
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Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 1:28 AM

Right on..

RF_Guy

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#62

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:19 AM

anyone out there has ever found any dangerous that connect the probe directly to mains wire by input attenuation at 30--60 step ?

is it danger than operating a multimeter on it?

how about if you make a mistake to set at current step or resistor step without careful.

Ronald's autotransformer cannt insolate set from mains, he may make a mistake at word of transformer. is it needing to make a such fuss on him?

back to a step, even if he connect the autotransformer to mains, can it definitly hurt body if you use the oscillascope probe connect to it?

can you analysis completely?

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#63
In reply to #62

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:35 AM

Thank You so much cnpower. We need more people like you!

You have my utmost respect and admiration for your wisdom! Well said...

Good Job!

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#64
In reply to #62

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:39 AM

Your English is better than my Chinese, but not by much.......by the way, my Chinese is almost non existant. Your posts are sometimes too clipped and not easily readable....I am sure that your spoken English (I have worked in the far east many times) is far better. That is quite normal....

One should never criticize safety, it is a very damning failure to do so.....if the situation deserves safety comments according to anyone here on CR4, we will put safety comments in. You are going against a well meant rule followed by many, but not all......i could name at least a dozen more that do not agree.....but does that make it right? No and we do not want accidents.......at least most of us do not!!

If you are not able to realise that it is "Teamwork", but to feel criticised, then you have to also learn to grow up!! Or leave, you have a choice always.....

I hope that you receive this friendly advice in the same friendly fashion that it is sent to you.....

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#69
In reply to #64

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:17 AM

you are wrong, as matter fact, I cannt speak even one Englsih word.

its just unreadable, I hope you point out and then I can correct it as other done. sorry for it will waste your time.

I wonder what is teamwork here? anyone can offer his suggestion, others can object it. its normal. I hope to see the normal reason to rebut. not only" dont agree " etc.

I dont know why select leave? Do I offend you all? Is my words of direct connection to set heavy wrong?

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#77
In reply to #69

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 9:07 AM

We don't really mind the quaint English, but most (not all) of us want to see that recommendations have any points of danger, contact to the mains for instance, to be remarked on.....a good pupil will not object!

We DO want that nobody is injured in any way......its as simple as that!

I would like to point out that you hear from me EXACTLY what I feel you should hear.

Several people have emailed me (I do not blame them, they shall not be named by me) who do not approve of NOT including safety infos by you and several other people, but they are a little bit afraid of telling you or the others directly, but they support me, the safety Guy!!.....so I am not alone......

CNPOWER, we need you here with your knowledge and ideas, so do not be upset, there really is no need for that. We will always add the safety infos if you leave them off..... teamwork!! Or if anyone else does!! Everyone forgets something......I forget the spell checker FAR too often !!!!

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#65

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:44 AM

The first thread only hope to know if he can commenct his probe to mains and simply to know the waveform. isolation transformer is a good idea to everyone. but what quality one he will select? if the transformer is not good enough, it can also make harm to him. so he much choice it carefully.

if you want to see a spike, but if the transformer is very narrow band, he would see nothing.

what is safety? if you dont keep careful any time. no safety anywhere.

only below 36voltage is safety voltage.

if you take not careful, even a telephone line can harm you. dont belive?

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#67
In reply to #65

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:00 AM

May I recommend that you learn the difference between the Sublime and the Ridiculous....

Although if you strongly feel that ALL safety points, no matter how ridiculous should be entered, I will stop complaining as that is a far better area of failure than omitting them completely.....

I wish you a long and prosperous life and good luck for the Chinese New year 4706 which begins I believe on Feb. 7, 2008. The year of the Rat.

I was born in the year of the Dog, many years ago!!!

My Mother lived fully up to her years type until her recent death in 2005, she was born the year of the Dragon!!! Chinese years are very interesting and surprisingly accurate in character types!!!! Mine included!!

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#71
In reply to #67

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:39 AM

I wish every electronic engineer could deal every thing with science state.

Which can do , which not, should be analysised by theory. However, we are not simple labours. Safety is Very very dear dear for life. none make fun of it.

if one would convince other, he wuld take out facts. dont fear, but make carefully.

I will learn from everyone out there anytime anywhere.

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#73
In reply to #67

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:56 AM

Haha, you know some chinese culture. very good.

your west has 12 constellations, and our chinese has 12 animal signs (symbols).

next time I can post all of them.

In fact, I dont know what date is our next spring festival, I hve to read our " Huangli" (chinese words) and then tell you all.

its very interesting like your christmas.

chinese belongs to far east, you may work in Japan. so you know spring festival, cause they have also this festival.

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#70

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:36 AM

OK, OK, enough already! In my haste to answer I chose the wrong wording. I should not have said what I said. Like cnpower tried to explain. I have used them to test ac to dc power supplies. My Bad to recommend, it should be done by trained persons only.

I was under the impression that "most" of our guests were!

Then I got a little annoyed when whom ever it was said that I should...so on and so forth...I've already forgotten!

Please lay off the other guy! He only tried to defend little old me. No beef with the rest of you!

Stop Now, OK! Enough.

Let's Move On.

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#74
In reply to #70

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 4:43 AM

Dear ronald,Only for ronald,

Get your variable transformer,connect it to the mains,preferably 230v,turn it to 36v 'safe' output.

Wet your finger and touch the '36v' output.Let us know how it feels. Experienced engineers may not want to try this. Dont do this at home,really,dont.

If you survive you will have learnt an important lesson

If you dont you will no longer be a danger to others.

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#78
In reply to #74

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 9:09 AM

OOOUUUCCCCHHHH!!!!!

It will only hurt for a very short time.......an ELCB will probably save your life, but I know from experience with them, that it still hurts!!!

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#80
In reply to #74

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 11:26 AM

http://www.variac.com/staco_3PN10_20.htm

DVM and XDVM Models Include Digital Voltmeters, DAM and XDAM Models Include Digital Ammeters.

DVAM and XDVAM Models Include Digital Volt and Amp Meters.

Variable Transformers

Staco Energy Products' full range of variable transformers offer the exceptional versatility and reliability required for so many of today's voltage control applications in both industrial and laboratory environments.

Unlike a standard fixed ratio transformer, a Staco variable transformer is designed to provide variable output voltage that can be adjusted from 0 to 117% of the unit's input voltage.

Staco Energy Products Co. offers a wide range of standard models including the following:

· Panel mount, single phase (fixed and adjustable shaft)

· Enclosed cord and plug

· Metered

· Fully enclosed

· Ganged

· Isolated

· Isolated portable cord and plug models

· "Quick-Step" motorized

· Motor driven

· Cased

A basic Staco variable transformer consists of a copper winding on a toroidal core of laminated, grain-oriented, silicon steel. A carbon brush, connected to an output terminal, is rotated over the length of a precision-ground, precious metal-plated, commutator track to tap off voltage at any turn from zero volts to the maximum output voltage of the winding.

http://www.variabletransformers.co.uk/vtweb2.html#reg

http://www.variabletransformers.co.uk/vtweb2.html#test

http://www.elect-spec.com/variac_tutorial.htm

Special Variable Transformer Tutorial Page

Although part of our regular tutorial series, this page is offered as a Stand Alone Variable Transformer / Variac Tutorial to accommodate the many request we have had for basic information on the subject.

You are invited to subscribe to our Free Tutorial ($400 Value) series. Sign up HERE for over 20 insightful, practical segments designed to help you get maximum service from your Hi-Tech equipment

Learn more about Variable Transformer products we offer -
Click here for Variacs
Click here for Variable Voltage Isolation Transformers and Voltage Regulators
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Click here for Stepper Motor Voltage Regulators
And here for Packaged Stepper Motor Voltage Regulators

Also, our FAQ pages discuss a wide range of practical problems and solutions based upon countless hours I have spent beating spikes, transients, surges and interference into submission. Check 'em out!

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http://www.google.com/search?sourceid=navclient&amp;amp;ie=UTF-8&rlz=1T4SUNA_enUS241US241&amp;amp;q=Variable+transformers

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#81
In reply to #80

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:12 PM

and on which page/link is the safety information?

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#82
In reply to #81

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 2:48 PM

I saved the best for last! Cuz I knew you would ask!

Nowhere on any page was there a warning or caution!

Assumption is that you should know this; the warnings come in a brochure inside the box and stamped on the device. Recommend you think as a pro "out of the box". I rest my case, and proved my point!

Buyer beware! Concerned? You look it-up, I'm not doing all the work for you!

Errr? Be a "Pro", you can do it, I'll be there pullin' for you! Or, do we need to hire Homer Simpson? Hmmm, dunno, maybe he can't; he's not an "E-n-g-i-n-e-e-e-e-e-errrrrrrrrrrrrrrrrr"! If you have any doubts...Please refer to the Warning at bottom of page!!!!!!!!!!!!!!!!!!!!

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#85
In reply to #81

Re: How Do I Connect Mains To Oscilloscope Input?

12/21/2007 3:36 PM

Cant find any isolation types in the first two links,but on the Variac site they have a vt in a box with an isolation transformer.

The accompanying blurb says 'isolates the engineer from hazards associated with working on live equipment',but doesn't mention the limitations of protection,you still have 120/240 v potentially on the item connected,even if you cant get a belt from touching the live alone.If you have a neutral-earth leak or fault on the connected equipment you are back to the original shock hazard if you touch the live.

Im a bit paranoid about 'scopes as the traditional metal cased ones are at the mercy of what you connect the croc clip to.And sometimes what the probe is connected to.

Testing power line equipment at 1200kV I had a massive trolley mounted 'scope to record wave fronts.The 'probe' was connected to a capacitor divider 5 metres high,the bottom capacitor was a solid mica plate device with the 'scope input connected to the live end the other end being earthed.

On initiating the test voltage a massive spark jumped from the 'scope case to the doorframe 0.5 metres away.There was a smell like Lucifer had paid a visit.

After changing my underwear investigations revealed that the mica capacitor had disintegrated,giving most of the 1200kV to the 'scope.We fitted a huge vdr to the stack bottom,a spark gap,and a thick earth braid to the new 'scope. Being a bit of a wimp any future examination of live waveshape I did with binoculars,or just let the camera do the work. Paranoi excused?

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#101
In reply to #85

Re: How Do I Connect Mains To Oscilloscope Input?

12/24/2007 1:46 AM

1200KV? wonderful test!

what Ive ever tested the highest voltage is below 300Kv. I can ony see this boltage at picture or tv program.

your capacitor divider of 5M high is must in open air.

how much frequency is it? 50/60?

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#103
In reply to #101

Re: How Do I Connect Mains To Oscilloscope Input?

12/24/2007 10:57 AM

Hi cnpower, Do I detect disbelief? Tests were on power line insulator strings.Laboratory now defunct,as too small for tests needed on 625kV lines.(arced to walls,ceiling etc)

See enclosed photos,actual test at 50Hz,flashover at about 1500Kv,power from two 265kv transformers in cascade,about 250mA. Read with telescope on secondary transformer meter.

Impulse generator,not the one I worked,but very similar. I had stack of capacitors in fours,note capacitor divider at the front.Charge capacitors in parallel to if I remember 150kV,discharge in series .Voltage calibrated by 2M sphere gap.Not in open air,in huge shed.

Oscilloscope problem was on impulse test,therefore DC,with rise time set by resistors,oscillogram photographed for validation.

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#104
In reply to #103

Re: How Do I Connect Mains To Oscilloscope Input?

12/24/2007 11:35 AM

Hey!

I saw a rig like that at Harvey Hubbell when I did some QC there about 5 years ago! It made a very loud BANG!

I think they were testing Lightning Arrestors!?

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#106
In reply to #103

Re: How Do I Connect Mains To Oscilloscope Input?

12/25/2007 11:49 PM

Hi, Oldeng (LaoDeng?)

It seems you work in a super hv field. its still open air lab.

I wonder your words, two 265kv transformer cascade together can be connected to a 530kv mains, what means is 625kv? how much is a 265kv transformer beared?

read by a telescope? why dont you lead the meter to outside for read conviniently?

you said 2M gap? is it 5-10cm gap for 150kv discharge?

why dont use a digital oscilloscope for impulse tst?

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#108
In reply to #106

Re: How Do I Connect Mains To Oscilloscope Input?

12/26/2007 10:44 AM

Hi cnpower, If you are going into pinyin you should address me as 'lao gong cheng shi/hui ling'.

I dont think we should hijack this discussion while I tell you how to set up a high voltage laboratory. Ask a suitable question,start your own thread,we will get far more experienced answers than mine.

However since in the West its Christmas I expect the members to indulge me and I'll answer your latest,please bear in mind that it is 50 years ago so some of the 'facts' may be wrong!

Lab was to test power line insulators up to 625kV line voltage.Insulators had to test not to flashover at about 1500kV.DC tests with test waveform specified by CEGB, AC tests at 50Hz,wet simulated rain with deion water and dry tests.

Transformers were in CASCADE not series,i.e.first transformer physically on the ground,the secondary fed the primary of the second transformer which was on a massive paxolin tube,see photo in last post.Have a picture of two transformers,but cant find it.

As the tank of the second transformer was at potentially 265kV to ground the attached voltmeter leads would also be at 265kV,I dont think you want to be close to that to read it,hence the telescope.

The 2M sphere gap refers to the diameter of the spheres. The gap could be up to 10M to measure 2million volts,although the spark went sometimes to the wall or roof instead as the lab was too small.

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#110
In reply to #108

Re: How Do I Connect Mains To Oscilloscope Input?

12/28/2007 1:24 AM

Oh, I see, you are very familiar with Chinese. You are senior engineer.

The transformer is eventually a voltage mutual inductor. The first connected to 625kv line then its secondary turned into 265kv, and then connected with the primary turns of the second voltage mutual inductor, which shown in the photo. Does my comprehensive right?

If right, the meter will connect into its secondary turns to give a read.

I like to post new thread on the topic, but Im afraid none is interested in it. I remember I posted a thread about Tesla coil several month ago, but none responded. Lets talk here, and this may has some relation to the top thread.

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#111
In reply to #110

Re: How Do I Connect Mains To Oscilloscope Input?

01/03/2008 12:28 AM

its pity , havnt yet get your reply on the question.

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#99
In reply to #74

Re: How Do I Connect Mains To Oscilloscope Input?

12/24/2007 12:11 AM

Haha, so hot discuss continue. you all seem to make Ronald as a target, but you are going so far extrem off the top thread. I like challenge and continue this topic. Im strange at your these words. I think if you have ever learnned some college electric course, and still dont forget some of them, you will know what is the potential? what is differnece between potential and voltage, and then you will not post such answer. 36v from autotransformer? what does it mean? What important spot do you forget?

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#100
In reply to #99

Re: How Do I Connect Mains To Oscilloscope Input?

12/24/2007 12:28 AM

none but a foolishman will touch a chassis with a wet hand. any trained electrocian will know to test running machine temperature by back of hand touching surface of equipment like motor etc. you are must making a kidding.

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#102
In reply to #99

Re: How Do I Connect Mains To Oscilloscope Input?

12/24/2007 10:50 AM

Hey cn_power! Want real action and adventure?

See the one about the LCD TV screensaver...

It's still playing, though I doubt you'll get it on DVD.

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#105
In reply to #102

Re: How Do I Connect Mains To Oscilloscope Input?

12/25/2007 10:55 PM

Hi, are you from Puerto Rico or from USA?

I hve thought thats a small country in south america

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