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Measuring line noise and power conditioners

I recently purchased a Trifield EMI (Dirty Electricity) Line Meter to measure noise coming from my outlets. To my surprise, my $500 power conditioner (name withheld to protect the potentially innocent) appears to not filter any noise per the Trifield readings. In fact, with some of my outlets the measures are higher through the conditioner’s outlets, than the measures coming straight out of the wall. The manufacturer denies anything is wrong with their conditioner, claiming the Trifield is measuring the wrong frequencies. Can anyone explain?

output555

Showing 4 responses by erik_squires

erik_squires
16,644 posts
 
In your recent responses, you say RFI. We are referring to EMI.


My bad.


What I hear ain't luck. Having a device that can measure what I hear ain't luck.

Coincidence and bias are real, which doesn't mean you haven't done enough experimentation to eliminate them, they are just the first to things to eliminate before claiming more.

erik_squires
16,644 posts
 
My point to all of this is that cleaning up AC noise in the audio frequencies is as important or more than RFI. We should be looking at devices and measurements which clean up both.

Think of most power conditioners as essentially filters, much like the crossovers in a speaker.  Signal comes in, some passes, some gets blocked. The ideal power conditioner (as opposed to a regenerator) passes 60 Hz (or 50 depending where you are) and blocks all others.  RFI filters are low pass filters.  If you can go lower, and start at 3-10 kHz that's better than starting at 100 kHz.

Notice I'm not talking about any brands you may like or not like.  I'm just stating principles.
erik_squires
16,644 posts
 
It’s hard to imagine noise on your line only affecting one portion of the frequency range. So in other words if you reduced noise that’s being measured above 20khz why wouldn’t you expect that same filtering to affect the entire range even in areas that aren’t being measured by the meter?

This problem is kind of a Venn diagram.  A conditioner which starts at 10 kHz will hopefully also clean up 100 kHz.  A  conditioner which starts working at 100 kHz won't necessarily clean up 10 kHz.

Of course, coupling can occur later, and there will be a frequency high enough that it stops working at too.

So, you have a meter which measures RFI, which shows reduced noise, and the power conditioner happened to reduce noise in the audible spectrum too.  That's luck.
erik_squires
16,644 posts
 
If we are talking about this meter:


https://www.alphalabinc.com/product/plm/


You are measuring starting at 20 kHz and going up.  That is, these devices START measuring noise at the upper limit of human hearing.

While many surge protectors claim to block EMI/RFI, they also claim to start working in the 100kHz ranges, way higher than noise we'd hear.
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