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[Ike Zimbel]

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.

FWIW, I have a couple of Agilent/Keysight U1604A for sale. One of them works, the other one "works" but has an intermittent issue with the screen that I delved into briefly and narrowed down, but didn't pursue further. Available as a pair only, make offer. https://www.microlease.com/us/products/keysight-agilent-technologies/oscilloscopes/u1604a?basemodelid=4602&id=6&gclid=EAIaIQobChMImPiz1K3P1AIVnbXACh271wzQEAAYASAAEgJvEfD_BwE

[Kevin Conlon]

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

I was really thinking of seing  a nice smooth sine wave without jagged edges or flat peaks. I know i don't know much about the other factors that make up clean power. Most power suplies filter out a majority of ac power defects, at least thats my understanding. Thanks for the input, i have a lot to learn.

[Mike Sokol]

I was really thinking of seing  a nice smooth sine wave without jagged edges or flat peaks. I know i don't know much about the other factors that make up clean power. Most power suplies filter out a majority of ac power defects, at least thats my understanding. Thanks for the input, i have a lot to learn.

That's the "stepped" sine wave you get from a cheap inverter. A real AC generator with spinning coils and such simply can't make that stepped waveform. The physics and geometry guarantees a pure sine wave. However, a cheap inverter generator (DC generator with an inverter output) from China could make that kind of noise from a stepped sine ouput. I should note that modern Honda and Yamaha Inverter generators make really excellent sine wave power (or as close to perfect as it practical) and have never caused me any noise issues. 

[Stephen Swaffer]

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.

Most noise and distortion in power circuits caused by the load-so I would expect a "real generator" in an unloaded situation to show much cleaner power than your wall receptacle.  The most likely problems would be voltage or frequency out of tolerance-if those are good I would expect the sine wave to be correct.

From my experience, power quality analysis is beyond the reach of most casual users.  Even if you have the tools to make the measurements, there is quite a bit of interpretation to it-then again what are you going to do about it?  I just got test results back yesterday from a test we had done-what "I can do about it" is add line reactors on VFDs and a capacitor bank on the incoming power-beyond anything most are going to do at a gig.

[Tim McCulloch]

Most noise and distortion in power circuits caused by the load-so I would expect a "real generator" in an unloaded situation to show much cleaner power than your wall receptacle.  The most likely problems would be voltage or frequency out of tolerance-if those are good I would expect the sine wave to be correct.

From my experience, power quality analysis is beyond the reach of most casual users.  Even if you have the tools to make the measurements, there is quite a bit of interpretation to it-then again what are you going to do about it?  I just got test results back yesterday from a test we had done-what "I can do about it" is add line reactors on VFDs and a capacitor bank on the incoming power-beyond anything most are going to do at a gig.

Exactly, and that's why I think Kevin C needs to read Guy Holt's posts.

I appreciate your clearer explanation - that it's almost always a LOAD that creates the dirt.  Very little waveform distortion occurs on the utility side or with "real" spinning coils generators.

[TJ (Tom) Cornish]

I was really thinking of seing  a nice smooth sine wave without jagged edges or flat peaks. I know i don't know much about the other factors that make up clean power. Most power suplies filter out a majority of ac power defects, at least thats my understanding. Thanks for the input, i have a lot to learn.

Seeing a nice-looking waveform is academically interesting, but again it doesn't tell you much, and adds zero options for you, other than a probably fear-based reason to not do the show.  If your scope does measurement rather than just a waveform picture that helps a little bit, but scopes are pretty low-resolution, and many of them just measure from the on-screen waveform, meaning the numbers are pretty low-confidence.

Even the nicest oscilloscopes will not show most show-critical issues by themselves - they need test jigs and multiple measurements to do the job, and even so, the result will be lower in resolution than a good meter.

Seriously - take a look at the Extech CT-70.  This will reveal all show-affecting issues except RPBG.

Here is a procedure I wrote up for evaluating power that may be helpful for you:
http://tjcornish.com/articles/power-and-electricity-artic/receptacle-testing.html

[George Friedman-Jimenez]

Nice simple explanations in your article Tom, thanks. Can we do pretty much the same as the CT70 with a heater load on a receptacle in parallel with the receptacle being tested, a multimeter and a small 3 light receptacle tester like the ET10, which most of us already have?

[Frank DeWitt]

BTW A "real generator" is one that produces good usable AC power.  I have a 1947 Kohler.  Lots of iron, lots of Copper, runs at 1200 RPM, powered by a 4 cyl water cooled engine, running nice and quiet. It's output is on a couple of threaded terminals.  Like a Honda Inverter generator, it is a "Real Generator"

[TJ (Tom) Cornish]

Nice simple explanations in your article Tom, thanks. Can we do pretty much the same as the CT70 with a heater load on a receptacle in parallel with the receptacle being tested, a multimeter and a small 3 light receptacle tester like the ET10, which most of us already have?

Yes.  A multimeter and a load are all that is required to test a receptacle pretty thoroughly.  The CT-70 is just an automated convenience.

The 3-light tester is indicative of some basic wiring faults, but it doesn't do anything that a multimeter won't do, and it isn't a complete test, so you can skip that one.

[George Friedman-Jimenez]

The CT70 saves having to carry around a heater in the summertime, and the little noncontact tester can help identify a RPBG that the multimeter and CT70 would both miss, so the CT70 OR multimeter plus a noncontact tester would be a complete set except for missing major deviations from sine waveform. I liked the 3 light tester plus noncontact tester as a quick screen, but you make a good argument that without a parallel load, those won't find excessive voltage sag under load. What do people think is the value added of looking at the waveform under load? Worth doing?

[ProSoundWeb Community]