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Old 1st June 2011, 11:35 PM   #31
gpapag is offline gpapag  Greece
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Quote:
Thanks George, Was worth checking!
It HAD to be checked. I had checked it in the past and I was certain that the card was OK, but I had not documented it.
Now it's done properly!

Quote:
The effect is quite subtle, I have no ideas as to what might be causing it.
After an additional couple of hundrend MB of measurement data and 2 man-days work , I have gathered enough evidence to target the cause ("Pretty elementary dear W")

I'll just till tomorrow's daylight.

Regards
George
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Old 2nd June 2011, 10:05 PM   #32
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keeping me in suspense?? It's now morning here is Aus George Maybe you baked a few more transformers and now need to recover?

Tony.
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Old 3rd June 2011, 05:22 AM   #33
gpapag is offline gpapag  Greece
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Ah Tony
I’m 3 days with no baking!
Yesterday morning I went to my lab for “half an hour”.
I ended up doing manual measurements for 10 hours.
In the end I could not gather which probe goes to where. My head was like our economy here par the “cooking”.

I thought to sit and type a few lines as an apology for not being on time on this thread, but I was somehow certain that you guys would had already set your mind that I was fully –arms and legs – into baking, therefore I droped the idea.

I had a couple of beers instead and went straight to bed.
The Wagnerian style “where had you been the last 48 hours?” clinked familiar to my ears.

Today MORNING I’ll do some hours “MS Paint” editing and you’ll have some more nice colourful diagrams, just to add to the confusion.
See you later
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Old 3rd June 2011, 07:33 AM   #34
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I hate it when that happens "1/2 an hour turning into 10" Can completely relate to it!

Take it easy George, I'm in no rush

Cheers,

Tony.
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Old 3rd June 2011, 09:18 AM   #35
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Thanks Tony

Here we go (just 16 min past noon )
Again, 20Hz roll-off dBs rel to 3kHz level.
On the right is the signal level entering the Sound Card in dBs relative to 0dB (1286.4mVrms) of my Sound Card

Ch1 Out-Old X-H-L
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File Type: jpg Old H-L overlays.jpg (158.3 KB, 38 views)
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Old 3rd June 2011, 09:21 AM   #36
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Ch1 Out-Old X-L-H
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File Type: jpg old l-h overlays.jpg (170.3 KB, 33 views)
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Old 3rd June 2011, 09:23 AM   #37
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Ch1 Out-New X-H-L
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File Type: jpg New H-L overlays.jpg (159.0 KB, 7 views)
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Old 3rd June 2011, 09:26 AM   #38
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Ch1 Out-New X-L-H


Regards
George

PS. Next burst of measurement data, later on
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File Type: jpg New L-H overlays.jpg (156.7 KB, 7 views)
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Old 3rd June 2011, 11:13 AM   #39
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What is seen from all the above new plots (including the one from the 1:1 bifilar in post #28 Implementing a “Y Out” on an Oscilloscope

is that the LF roll-off drop in dBs btn the 3 x-formers (5 different connection configurations) as well as the difference of LF roll-off drop btn high level and low level signal in each connection configuration, is affected by the secondary load, as reflected back to the primary. The lower the reflected impedance, the more dB drop. (Electric circuit theory predicts this by the way).

As for the 50Hz plus harmonics peaks , I can not propose any relationship btn the peaks amplitude (highest is 36db height, lowest is 15dB) and different configuration, as each measurement was c/out at different time (*PS), although each curve on every diagram is the average of two ~5sec sweep measurements. The less noisy seems to be the “New” x-former, but only simultaneous measurements can confirm this.
The only think that is certain is, that the 50Hz pick-up is due to the x-formers themselves and not from the interconnects. This is shown up to now from curve “C19” in bifilar diagram and from the lower green curve here Implementing a “Y Out” on an Oscilloscope

It was to be expected, as all these x-formers are of unshielded E-I construction.
Some measurements I’ll show you later, will support this opinion.

Regards
George

<Edit>
*PS 1.That the 50Hz pollution varies with time is manifested by the harmonics. On some diagrams you’ll notice that some harmonics are positive going on one curve, while on an other curve on the same diagram they are negative going.
*PS2. Literature says that the amount of 3rd, 5th and 7th and the relation of their height, is a metric of the load unbalance btn phases on 3phase utility distribution network.
In my lab I have only one phase of 230V and I try to keep the same condition as to the equipment that I operate plus lighting, as well as all the measuring wiring is in the same position (taped to the workbench) during all these experiments.
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Last edited by gpapag; 3rd June 2011 at 11:43 AM.
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Old 3rd June 2011, 12:42 PM   #40
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Hi George, I'm still digesting this information (I'm a bit thick sometimes when it comes to electrical circuit theory)

It is interesting that the 50Hz and harmonics behave the way they do, but as you said test to test is not really comparable (as I have found).. I got some measurements early on with virtually no 50Hz polution and have not been able to replicate

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