120VAC line to line-level for AC line analysis. Has anyone done it ?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Silvas

Well-known member
Joined
Aug 15, 2006
Messages
727
Location
Chia, Colombia
Hello !

I had this idea where somehow  i can connect the AC from the wall to an AD for signal analysis, visualizing harmonic contents, THD and so as a way to characterize AC power coming out from the wall as well as inverters, online UPS systems and so. Has anyone here done something similar ? I guess it would be some sort of a pad followed by a stepdown transformer for isolation and safety...Anyone ? And yes i know i could simply scope it  ;D ;D ;D Best regards.

 
You can crudely just look at the output of simple ac to ac  wall wart that will drop the 120V to maybe 15VAC

The bandwidth of the wall wart is not great but lightly loaded you can see what is going on.

JR
 
JohnRoberts said:
You can crudely just look at the output of simple ac to ac  wall wart that will drop the 120V to maybe 15VAC

The bandwidth of the wall wart is not great but lightly loaded you can see what is going on.

JR

It totally makes sense !  :D Thanks !
 
Silvas said:
I guess it will need some loading tho.
Care is needed switching a highish voltage on to, or off, any transformer, not just an output transformer.    The worst outcome is that an over-voltage stress/arc can occur in the transformer primary winding.

It's not clear how accurately you want to view the harmonic levels, eg. the % HD level, or the span of the frequency spectrum, or ...?

You could also just extend the input of the ADC close to an insulated wire carrying mains voltage.  Capacitance coupling will give you quite a good view, and out to the frequency limit of your ADC.
 
ruairioflaherty said:
I use one of these for looking at the mains with a scope

http://www.gryphon-inc.com/PDF%20Literature/Power%20Probe%20-%20AC%20Line%20Viewer.pdf

I wasn't aware that such gadget existed, thanks so much for pointing me out to it !
 
I've had the VERY similar OneAC unit for years.  Here's one currently listed:

https://www.ebay.com/itm/Oneac-Line-Viewer-103-LV103-with-hard-case-manual-and-cables-ESTATE-FIND/292388882808

Bri
 
Brian Roth said:
I've had the VERY similar OneAC unit for years.  Here's one currently listed:

https://www.ebay.com/itm/Oneac-Line-Viewer-103-LV103-with-hard-case-manual-and-cables-ESTATE-FIND/292388882808

Bri

I just made an offer for it and the guy accepted USD40  ;D ;D ;D ;D Thanks Brian for pointing me out to it.  I guess i'll have some fun with it.
 
Brian Roth said:
My OneAC box has come in handy a few times when tracking down funny noises in recording studios.

Bri

Guess what ? I landed here : https://www.gearslutz.com/board/geekslutz-forum/502071-ac-power-noise-sniffer-60-hz-hum.html
 
I read an article on someone servicing tube amps and he had a standard light bulb in some weird configuration..
 
efinque said:
I read an article on someone servicing tube amps and he had a standard light bulb in some weird configuration..
It's a very common trick-of-the-trade. Wire the light bulb in series with the gear you want to soft-start. If the device is shorted, the bulb lights fully and limits the current to the value  determined by the bulb's power. If the gear is behaving correctly, the bulb will briefly light at start-up and then dim.
I have such a contraption at the ready, and not only for tube amps; last time I used it was on my portable PA on which I had replaced a shorted output device.
 
abbey road d enfer said:
It's a very common trick-of-the-trade. Wire the light bulb in series with the gear you want to soft-start. If the device is shorted, the bulb lights fully and limits the current to the value  determined by the bulb's power. If the gear is behaving correctly, the bulb will briefly light at start-up and then dim.
I have such a contraption at the ready, and not only for tube amps; last time I used it was on my portable PA on which I had replaced a shorted output device.
Yup, often the light bulb was wired in series with a variac to help with amp repairs. Slowly bring the rails up until lamp does not light, then you can short across the bulb for full power testing.

JR
 
The OneAC live viewer is here ! Seems like a fun gadget and quite useful for a tech-savvy obsessed with perfection mastering engineer like me. Coupled with some analysis software you can get an FFT of your AC line common and normal mode noise (depending on your software and sample rate) and you can also take a look at the quality of your AC including a THD readout (maybe useful for characterising AC inverters from UPS units and so ?)

I guess i can record the outputs at 192K on a three-track session on protools for long-term analysis too.  This was exactly what i envisioned on my original post.

Brian Roth said:
I've had the VERY similar OneAC unit for years.  Here's one currently listed:

https://www.ebay.com/itm/Oneac-Line-Viewer-103-LV103-with-hard-case-manual-and-cables-ESTATE-FIND/292388882808

Bri

Again, thanks Brian for pointing me out to it.  :D:D:D:D:D:D
 

Attachments

  • DSC00002_DxO 2048.jpg
    DSC00002_DxO 2048.jpg
    581.3 KB · Views: 11
Is this to be a tool to meet a purpose (ie. with specs or requirements of some kind related to steady signal magnitude or frequency or transient characteristics - and related to a detrimental performance of some equipment that might be affected by anything other than single frequency with constant amplitude mains) or to equipment that may generate detrimental signals?
 

Latest posts

Back
Top