EMI and Ferrite Cores
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@MattSpeller said:
didn't really give what m
Thanks Matt. I appreciate the offer of help.
I have attached a screenshot from the monitoring software. Yes the 180Hz signal should not be present, or at least prevalent in the pictures. He is reading very low frequency electrical impulses and this signal is throwing off the tests.
He is sending me the model numbers of the equipment in the morning. In the meantime, could you help me pick out some ferrite cores that may be able to help filter this 180Hz (3rd Harmonic?) interference? I was about to order some, but then I noticed that there were different types for different frequencies, and I cant make heads or tails of which one I need.
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@Brains Alright, well from what I remember I don't think chokes work that way - at least how you want it to in this instance. I will have to read up on them again to make sure I'm correct there!
Onwards; 180hz is super low and an odd one. 3rd harmonic of the 60hz powerline, no doubt that could be the source. Unusual to only see the harmonic though, do you also see 120 & 60? (60 should be a huge spike if it's AXT (alien cross talk) from a transformer or something nasty). You've already tried isolating it from outside noise and it sounds like you did a pretty good job of it.
Next up I'd look at the device it's self and read it's manual. I'm willing to bet it has internal filters for this kind of thing - if not I'm almost certain that it'll mention how to deal with AXT as it's such a sensitive device you won't be alone in having issues with interference.
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Thanks for the followup Matt.
I went through some of the logs of tests performed. When there was a transformer close, it definitely cycled every 60/120/180, but with everything turned off, this is what we see
He has spoken with the manufacturers of both devices and they have been of no help unfortunately. When I get the model#'s tomorrow, I will try to give them a call and see if we can have a detailed conversation about our options. I do not expect this to be productive as the user using this equipment is pretty intelligent and understands some of this better than I do and was not able to glean any information. I am very good at cutting through red tape and double talk from tech support, so maybe I will be able to get something helpful.
FYI he is usually using a desktop to perform these tests, and the problem is apparent on both the PC and laptop (Laptop is unplugged of course)
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Very interesting
If you have access to an oscilloscope or a signal gen you could probe it out a bit further... very intrigued and I hope you let us know how it plays out!
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Page 5, try self calibration
http://www.thoughttechnology.com/pdf/manuals/SA7510 rev. 7 ProComp Infiniti User Manual.pdfTry replacing the fiber - that shit breaks so easily and I'm guessing the Doc isn't familiar with using it
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@MattSpeller so you think there may be a small break in the fiber that could be letting the EMI in, its just not bad enough to cause the unit to stop working?
Ill send this over to the user and ask him to try it
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@Brains just trying to think of the most common things to break - fiber is always top of the list.
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@MattSpeller awesome. He is receptive and will take care of that this weekend or Monday. I am open to any ideas, I was also wondering if it might be a case of "dirty power" in the building? Maybe we have some feedback from the AC Units being sent back along the line? Since this happens in many different places in the building, maybe we could install something to "clean up" the power. Before today I always considered those power cleaners a scam, but this seems like the intended usage if I ever saw one
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@Brains Power cleaners won't help you*, but I do recommend you try it outside the building in a big field or something.
*the units are battery powered IIRC
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@Brains said:
@MattSpeller Maybe we have some feedback from the AC Units being sent back along the line?
I've seen huge underground transformers cause bullshit like this before with testing gear.
Edit: they're not typically under the building though... -
I know it has been a while since I last updated, but we finally came to a resolution a few weeks ago and I haven't had a chance to update yet.
And....... it completely disappeared without a trace. haha well that is typically my luck so I wasn't too surprised.
We were able to walk around with the equipment and a laptop across the entire property, and believe we did identify the cause as our next door neighbors. They are a medical facility with some MRIs, so maybe their equipment was failing and they replaced a part.
One piece of additional information, I was able to have some really good conversations with their tech support and learned that they do have internal filters for 60Hz so that explains the absence of a 60Hz signal. I appreciate all the help from everyone on this forum. It was my beacon of light in a sea of confusing data.
Hope you guys are having a good April 1st. Don't trust everything you read
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I've used Ferrite cores a lot with cat5e on cell towers to block RF from the cellular antennas.
