Checking for "dirty" a.c. power with an o-scope - Page 3 - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 1st January 2013, 01:25 PM   #21
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: South Florida
The Newegg scope should be fine for isolated line testing and general audio work in low voltage amps.Do not plud the probe directly into the wall outlet. The 400 volt maximum input rating is too low for poking around inside tube amps without a 10:1 voltage divider scope probe.

Quote:
Where would that wave-form on that display be coming from??
That is an ideal sine wave. Your power line SHOULD look like this.....it won't. That trace is from a signal generator, or Photoshop.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 1st January 2013, 04:12 PM   #22
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
In another forum, Occam wrote:

Powervar acquired OneAC in 2011. I'm not positive, but the PowerVar line viewer appears to be the same as my unit, a OneAC line viewer, model 103. A 103 just sold on EBay for $90 -
OneAC Line Viewer 103 | eBay
The unit outputs common and normal mode noise on 2 different BNCs, as well as the ac waveform on another bnc, hence, the (ideal) requirement for a 2 channel scope for viewing. The input is a standard 15amp IEC inlet.

Powervar PP115 manual -
http://pdf.textfiles.com/manuals/STA...er%20Probe.pdf
it matches my OneAC 103 manual, no longer online.

FWIW,
Paul

You can skip the first posts in the thread:

6 Moons reviews - Blue Horizon Mains Noise Analyzer
__________________
Kevin
  Reply With Quote
Old 2nd January 2013, 01:33 PM   #23
Huck50 is offline Huck50  Canada
diyAudio Member
 
Join Date: Jul 2008
Thanks! Huck50
  Reply With Quote
Old 4th January 2013, 02:12 PM   #24
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
I think I said it earlier, but the issue with using a transformer to look at the AC waveform is that it will likely scrub all the higher frequency artifacts that are out of the bandwidth of the xfmr... like RFI and anything in the higher ultrasonic range.

I guess that is ok, but a bunch depends on what sort of distortion you want to see.
So, definitely it is ok to start with the output transformer and see what is there, it's somewhat safer since you have a stepdown ratio and lower voltage at the output side.
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 6th January 2013, 02:56 AM   #25
paba is offline paba  Canada
diyAudio Member
 
Join Date: Sep 2004
Location: Montreal
What about this little jig and then connected to the scope at the right side after the diodes?
Attached Images
File Type: jpg scope jig.jpg (20.6 KB, 145 views)
  Reply With Quote
Old 6th January 2013, 05:06 AM   #26
benb is offline benb  United States
diyAudio Member
 
Join Date: Apr 2010
First thing with that jig is to heed the 110 percent thing mentioned earlier. The second thing is those diodes will only convert the line signal into a square wave. Replace the diodes with a 100 ohm resistor and you have a voltage divider as discussed earlier. A quick calculation says the 10k is dissipating 1.4 watts - scale the resistor power rating accordingly.

If it's important to detect DC offset on the line (this would be useful to know - even a little DC can cause transformer saturation and overheating), you should have a direct connection instead of the capacitor.

Last edited by benb; 6th January 2013 at 05:09 AM.
  Reply With Quote
Old 7th January 2013, 12:36 AM   #27
benb is offline benb  United States
diyAudio Member
 
Join Date: Apr 2010
I tossed together this circuit in LTSpice - it should have the bandwidth of whatever opamp you use. The output is the same whether you ground either side of V1 or leave it floating. All that chances it the currents through R1 and R4. It does pull about 1mA from the line which would presumably go through the ground pin of the oscilloscope or computer's ground connection to the power line, which should be low enough not to trip a GFI.

Of course, remove the .txt extension to load it into LTSpice.
linemonitor.JPG
linemonitor.asc.txt

Last edited by benb; 7th January 2013 at 12:40 AM.
  Reply With Quote
Old 7th January 2013, 06:38 AM   #28
marce is offline marce  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Location: Blackburn, Lancs
It is also benefititial to record the mains over a period of time to record brown outs, voltage fluctuations due to loads on your mains etc, and if you are lucky someone near you will be using power line communications, it just adds more noise.
  Reply With Quote
Old 7th January 2013, 05:35 PM   #29
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
You can use an inductive pickup coil near the cord to pick up signals on that cord. -RNM
  Reply With Quote
Old 7th January 2013, 07:37 PM   #30
diyAudio Member
 
Join Date: Nov 2008
Location: Victoria,TX
Blog Entries: 1
Another suggestion is to use a current sensor. It will give you a milivolts output signal.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
"WTB" "The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral enantra Swap Meet 3 23rd December 2012 06:36 PM
"Quick and dirty" sealed subwoofer - HELP! Lenin21 Subwoofers 19 4th October 2011 09:29 PM
So now I have to worry about "dirty electricity"?? amt Everything Else 47 11th March 2011 06:57 PM
Fender Frontman 212R-Clean channel sounds "dirty" EronSilva Instruments and Amps 5 24th January 2011 05:50 PM
Early Punk Fans: "Talk Dirty" Lyrics? kelticwizard Music 0 30th October 2004 05:49 AM


New To Site? Need Help?

All times are GMT. The time now is 11:43 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2