Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Kevin Conlon]

Without searching for this maybe some of you may have a device [ scope ]that can see the purity of what the ac looks like that we are plugging into. Thinking a small scope that can fit in small "walk in " bag. Any help would be nice.
                                                       Kevin C.

[Scott Holtzman]

Without searching for this maybe some of you may have a device [ scope ]that can see the purity of what the ac looks like that we are plugging into. Thinking a small scope that can fit in small "walk in " bag. Any help would be nice.
                                                       Kevin C.

Something like this:  I have no knowledge of this model, there are many Fluke Scopemeter clones.  I am sure you can find one from a US vendor too.

Amazing compared to the 3k I spent on the real deal 20 years ago. 

Don't get some headless finicky Bluetooth thing.  Too fiddly, with a built in display it's as easy to use as a DVM.

http://www.ebay.com/itm/122364040354

[TJ (Tom) Cornish]

Without searching for this maybe some of you may have a device [ scope ]that can see the purity of what the ac looks like that we are plugging into. Thinking a small scope that can fit in small "walk in " bag. Any help would be nice.
                                                       Kevin C.

This is one of those things that seems like it would be useful, but really isn't. Even if you see something (a lot of the gunk is very intermittent- motors turning on/off, etc.), how do you quantify it? What do you plan to do about it?

AC power needs to be tested under load to reveal its colors. What you really want is something like the Extech CT-70 that shows you ground impedance, voltage drop under load, and miswired receptacles. If you want to go farther than this, a power quality analyzer is the next step but is very big $$$$ and still doesn't really give you any more actionable information than the CT-70, unless you are prepared to work on the building's HVAC, lighting, and power systems.

One other note - measuring mains AC with an oscilloscope is dangerous, as oscilloscopes are really designed for low voltage signals. Even though many have a range that can display line voltage, most oscilloscopes are ground coupled, so a miswired receptacle can fry your scope. The solution to this is a high voltage differential probe, which costs several hundred dollars itself.

[Kevin Graf]

When working on AC power line problems, the O-scope or meter needs to be battery powered. Connecting line powered test equipment can change or add to the problem.

[Kevin Conlon]

Something like this:  I have no knowledge of this model, there are many Fluke Scopemeter clones.  I am sure you can find one from a US vendor too.

Amazing compared to the 3k I spent on the real deal 20 years ago. 

Don't get some headless finicky Bluetooth thing.  Too fiddly, with a built in display it's as easy to use as a

http://www.ebay.com/itm/122364040354

thanks for that link. Might get one just to mess with.

[Frank Koenig]

When working on AC power line problems, the O-scope or meter needs to be battery powered. Connecting line powered test equipment can change or add to the problem.

Agree, for both safety and accuracy.

An employer once put me on a plane and flew me to Arizona to fix a "noise problem" with a piece of semiconductor manufacturing equipment. The techs in the fab could see the noise on the scope and, of course, as the engineer on the "analog board" it was all my fault. I put the scope on a ground cheater (yes I did) and the noise went away. What a waste of time and money.

Best,

--Frank

[Kevin Conlon]

This is one of those things that seems like it would be useful, but really isn't. Even if you see something (a lot of the gunk is very intermittent- motors turning on/off, etc.), how do you quantify it? What do you plan to do about it?

AC power needs to be tested under load to reveal its colors. What you really want is something like the Extech CT-70 that shows you ground impedance, voltage drop under load, and miswired receptacles. If you want to go farther than this, a power quality analyzer is the next step but is very big $$$$ and still doesn't really give you any more actionable information than the CT-70, unless you are prepared to work on the building's HVAC, lighting, and power systems.

One other note - measuring mains AC with an oscilloscope is dangerous, as oscilloscopes are really designed for low voltage signals. Even though many have a range that can display line voltage, most oscilloscopes are ground coupled, so a miswired receptacle can fry your scope. The solution to this is a high voltage differential probe, which costs several hundred dollars itself.

thanks for the info. I don't want to kill myself. Really more want to see if a genny is proper before renting, or if should use old amps instead of the good stuff. I know i can't change what i see nor would i know how. Peace of mind or worry about things. It would be cool to have in a distro box.

[John Roberts {JR}]

It seems we may have had a similar discussion before... what nature of power problem are you looking for?  A cheap wallwart power supply, with AC output could step down and isolate the mains power to something you could listen to... This may not reveal very HF interference, but problems in the audio range could be picked up.

JR

[Frank Koenig]

A cheap wallwart power supply, with AC output could step down and isolate the mains power to something you could listen to...

You can listen, or you can even run it into Smaart, etc., and look at the power spectrum (RTA). Just a thought. -F

[Tim McCulloch]

This is one of those things that seems like it would be useful, but really isn't. Even if you see something (a lot of the gunk is very intermittent- motors turning on/off, etc.), how do you quantify it? What do you plan to do about it?

The crux of the issue is in boldface.

I suggest Kevin C. taking a look at Guy Holt's profile and clicking on "show posts".  Guy has spent a fair bit of time posting about "dirty" power - what it really is, how it gets that way and what (little) can be done about it if the offending device(s) cannot be powered from a separate source.

The take away I got from Guy's posts is that many of the problems attributed to dirty power are failures or shortcomings in product designs or failures of grounding and bonding practices.

I've never had "dirty power" from a "real generator".  I've had unbonded neutrals, found loose internal connections, poor frequency control, etc.. but genuinely dirty power from an M-Q Whisper-Watt or similar generator?  No.

[ProSoundWeb Community]