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

trobbins said:

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?

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It's a troubleshooting tool. It works both ways, it can tell if the mains voltage is polluted/distorted and it can tell if a specific piece of equipment is polluting mains.
Now, we all know that conducted EMI/RFI is a bad thing, but thare are no hard rules as to what is acceptable or not and what are the consequences, although the UL/CSA/CE standards set limits.
Just an example: most electricity suppliers have to guarantee less than 10% voltage drift, but how it affects equipment varies a lot. Light bulbs may be more or less luminous, motors may be more or less powerful, but a computer may stall or go into overvoltage protection and your old style CRT TV may explode.

I was more asking Silvas about his use of such a tool.

There are many ways to measure particular characteristics.  The example of line voltage variation may be better measured by other tools.  That interface still needs to connect to a measurement device.  I'm probably like a few here, and would happily pick up a cheap exotic tool without having a specific immediate need.

trobbins said:

There are many ways to measure particular characteristics.  The example of line voltage variation may be better measured by other tools.  That interface still needs to connect to a measurement device. 

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Indeed. It depends what you're investigating. If your concern is voltage stability, you don't even need it. If your concern is frequency, you need a separate frequency counter. If your issue is with harmonic content or noise, you need a signal analyser. Some of these boxes have analysis capabilities, albeit limited.
The Monster Cable video fails to demonstrate that better results are actually achieved with filtered mains. Most current equipment is rather insensitive to mains pollution. Additional filtering can't hurt though.

abbey road d enfer said:

Additional filtering can't hurt though.

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My only caution would be that some diyers go over-board with mains line filtering, and the added filters imho would likely risk pulling more transients and harmonics in from the mains side than appreciated, and provide a perceived bandaid to a problem that is far better managed at the source of any issues.  And the decision to add such filtering is akin to using monster cables because the magazine advert paints such a rosy picture of performance improvement (ie. a solution looking for a problem).

+100

There is an entire sub-industry selling funny line cords and mains supply conditioning because phools apparently have too much money.  :

I responded early about using a wall wart because of my participation in sound reinforcement industry where mains power can be quite variable from gig to gig,,, and a safe way to sniff mains power for some random noise could be useful, but Abbey is absolutely correct. 99% of the time you can determine all you need to know with a basic VOM.

Further,,, people that claim to hear some magical benefit from using funny line cords or power conditioners, have just identified a poorly designed product that is overly sensitive to mains power that is routinely noisy.

JR

More on 'Light Bulb Tester' or 'Dim Bulb Tester'
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html

Hi All
Measuring the AC POWER line is easy with the proper equipment. I have used my AP’s (System One through the 2700 & other models). You can plug in the 120 volts to the balanced input.  Note: The input is limited to 200 volts peak. You can get an FFT from 24KHz to 1MHz plus depending on the instrument used. If your instrument is not a DSP model you can use it as a front end to a sound card or? The AP converts the signal from Balanced to UnBalanced  and the output level is 1 volt and 500KHz BW  plus.

I posted this on diyaudio, QuantAsylum QA400 and QA401 #2423. I have a full app note on this type of measurement. Send me an Email