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Topic: Mains noise analyzer?  (Read 4580 times) previous topic - next topic
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Mains noise analyzer?

There are few youtube videos with this device,
https://www.technologyfactory.eu/en/blue-horizon/blue-horizon-mains-noise-analyser/a-5717-320
measuring... what, exactly?
I've never measured mains power except voltage, so I am guessing there are some picked-up frequencies like TV and radio, induced currents form god-knows-where. I am pretty sure that power supplies filter out anything out of order, and we get clean DC for audio equipment.
So... what does it 'measure', and why is it there?
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Re: Mains noise analyzer?

Reply #1 –
Quote from: itisljar on
So... what does it 'measure', and why is it there?

Doesn't seem to be much in the way of technical explanation as to what it measures, so that makes me suspicious. I may be over-cynical here but I suspect the "why" is to part audio-fools from an extortionate sum of money by persuading them that they need it and then need to spend more on "conditioners".

Admittedly you need some technical knowledge and skill to use one but there have been "analysers" around for a very long time. They're commonly known as oscilloscopes! The price of admission for that "analyser" would buy a fairly high-spec 'scope with much better anaylsis than that device can hope to give - plus have 1000s of other uses.

You are correct that a competently-designed power supply filters out mains interference and you get clean (enough) DC. Any equipment which fails to do so, especially modern equipment, is either not competently designed or is faulty.  Yes there are odd problems encountered here and there, often not to do with "dirty" mains but they are the exception.

I live in the UK and our mains is somewhat flat-topped and has noticeable distortion and I'd expect most parts of the world to be similar or even worse. However, it's inherent in most power supplies that harmonic content is filtered to a greater extent than the residual mains content anyway and some flat-topping can be considered beneficial from most equipment's point of view (but not the power company's!).

Re: Mains noise analyzer?

Reply #2 –
Quote from: antz on
some flat-topping can be considered beneficial from most equipment's point of view (but not the power company's!).
this part got me interested, why is that?
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Re: Mains noise analyzer?

Reply #3 –
Quote from: magicgoose on
Quote from: antz on
some flat-topping can be considered beneficial from most equipment's point of view (but not the power company's!).
this part got me interested, why is that?
Because a flat-topped waveform spends more time at peak value, giving greater conduction angle for the diodes in the bridge-rectifier to recharge the smoothing capacitor. It means there's a small increase in supply efficiency or reduced stress on some components. There's also a small decrease in peak voltage due to the "missing" waveform tops. The argument is similar for most common switch-mode or linear power supplies. Imagine an extreme example - a square-wave supply. In that case the diodes conduct for very nearly 360 degrees of the cycle. A flat-topped "sine" tends towards that but a "clean" sine does not. In reality, the effect isn't major but it's there. And no, it won't muddle the sound, cause loss of "air" of any of the other usual audiofool stuff!

From the supply-network POV, the flat-topping is bad news because it implies a non-linear load where more current is drawn on the peaks (proportionately to, say, a resistive load) and proportionately little is drawn lower down the curves. That causes numerous issues such as excessive heating losses  and various other things the generation companies dislike.

EDIT: Actually, I don't think I've explained the first bit correctly. However, it does reduce the peak-to-average current on the rectifier and the capacitor ripple-current.

Re: Mains noise analyzer?

Reply #4 –
Quote from: antz on
The argument is similar for most common switch-mode or linear power supplies.
In linear power supply there usually is transformer first. And flat-topping is not good at all for transformers - less efficiency, more heat.

Re: Mains noise analyzer?

Reply #5 –
Very possible it measures the THD of the mains voltage, I have seen various power meters for electrical applications like the EasyLogic PM2200 (aprox. 250€) that do much more than simply measure the voltage THD.

There is and old pic project about measuring the THD, is a simplified version but informative: http://www.kswichit.com/PICTHD/picthd.htm

Re: Mains noise analyzer?

Reply #6 –
Quote from: Phanton_13 on
Very possible it measures the THD of the mains voltage, I have seen various power meters for electrical applications like the EasyLogic PM2200 (aprox. 250€) that do much more than simply measure the voltage THD.
There is and old pic project about measuring the THD, is a simplified version but informative: http://www.kswichit.com/PICTHD/picthd.htm

OK, let's assume it does that, with some loudspeaker yelling at user if THD is high - what does it do to power supplies, and to electronic equipment, for example amplifiers, and CD Players?
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Re: Mains noise analyzer?

Reply #7 –
Quote from: itisljar on
Quote from: Phanton_13 on
Very possible it measures the THD of the mains voltage, I have seen various power meters for electrical applications like the EasyLogic PM2200 (aprox. 250€) that do much more than simply measure the voltage THD.
There is and old pic project about measuring the THD, is a simplified version but informative: http://www.kswichit.com/PICTHD/picthd.htm

OK, let's assume it does that, with some loudspeaker yelling at user if THD is high - what does it do to power supplies, and to electronic equipment, for example amplifiers, and CD Players?

If it is a modern SMPS, it doesn't matter, since they'll take AC, DC or anything in between.  If you have some old linear power supply and there is a lot of harmonics you might heat up the transformer a bit, but since the harmonics are higher frequency they should still be filtered out.  In general, unless some supply is crap, it probably isn't assuming you have perfectly normal power, since in the real world that doesn't always happen.