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OverUnity Research > Benches > Itsu (Moderator: Itsu) > Smudge proposed NMR experiment replication.
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Author Topic: Smudge proposed NMR experiment replication.  (Read 127202 times)
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Re: Smudge proposed NMR experiment replication. « Reply #125 on: 2020-07-02, 19:36:25 »

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Apparently the server "thinks" that you are a dangerous hacker.

Yes, that would be twice this week then.


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If it is a galvanically isolated balun with 1:1 ratio then my answer is "between signal source and the caps".
If the balun ratio was something else than 1:1 then you could be tempted to match the impedance of the pancake coils to the impedance of the signal source transformed by such balun.


Its this one:  https://vk6ysf.com/balun_1-1.htm  using a T106-2 with 16 turns.

So not galvanically isolated.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #126 on: 2020-07-02, 20:05:45 »

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Quote from: Itsu on 2020-07-02, 19:36:25
So not galvanically isolated.
So it is not suitable for interrupting ground loops. :(
   
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Re: Smudge proposed NMR experiment replication. « Reply #127 on: 2020-07-02, 20:28:50 »

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These galvanically isolated 1:1 baluns are hard to find on the web.


In this case its just needed to balans the input signals into the pancake coils to minimize the crosstalk.


So should we really need to be able to completly avoid any signals on the output without any water in the tube?
I cannot imagine that being possible with coils that close to each other.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #128 on: 2020-07-02, 20:43:44 »

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Quote from: Itsu on 2020-07-02, 20:28:50
These galvanically isolated 1:1 baluns are hard to find on the web.
..but they are easy to make with a small ferrite toroid and non overlapped windings.  Also, old Ethernet cards are a cheap source of high bandwidth signal transformers which are galvanically isolated.

Quote from: Itsu on 2020-07-02, 20:28:50
In this case its just needed to balance the input signals into the pancake coils to minimize the crosstalk.
You are welcome to try balancing the sides and see how much that helps. We are here to learn as much as invent, after all.

Quote from: Itsu on 2020-07-02, 20:28:50
So should we really need to be able to completely avoid any signals on the output without any water in the tube?
Not completely but as much as possible. If the S/N ratio of the NMR signal will be too small to observe over the crosstalk, then there is always TDM to the rescue.

Quote from: Itsu on 2020-07-02, 20:28:50
I cannot imagine that being possible with coils that close to each other.
They should not touch - that's for sure.
Right now you don't even know whether the crosstalk is caused predominantly by inductive or capacitive coupling (or acoustic).
If the coupling is predominantly capacitive, a grounded shield between coils, (made out of Litz cloth so it does not impede AC magnetic fields) will make a big difference.
   
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Re: Smudge proposed NMR experiment replication. « Reply #129 on: 2020-07-02, 21:43:03 »

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..but they are easy to make with a small ferrite toroid and non overlapped windings.  Also, old Ethernet cards are a cheap source of high bandwidth signal transformers which are galvanically isolated.

You mean these things, see picture?  I got some out of a router.


I was doing some tests with TG/SA like you suggested, but allthough the input trimmer cap is working fine to tune the resonance, the output cap did not have any noticable influence so from that perspective it seems there is no visible crosstalk.

By the way, my old Tek scope does not show this 10Vpp gain/lose when connecting the FG trigger port to scope port 4.

Seems the new one is more sensitive in that area.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #130 on: 2020-07-02, 22:48:37 »

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Quote from: Itsu on 2020-07-02, 21:43:03
You mean these things, see picture?  I got some out of a router.
Yes, but the ones I found were much bigger.  Does yours transfer the synch pulse from the FG, even if it is only the edge ?

Quote from: Itsu on 2020-07-02, 21:43:03
I was doing some tests with TG/SA like you suggested, but allthough the input trimmer cap is working fine to tune the resonance, the output cap did not have any noticable influence so from that perspective it seems there is no visible crosstalk.
That's good news but I'd like to order a hookup schematic and a movie, please ;)

Quote from: Itsu on 2020-07-02, 21:43:03
By the way, my old Tek scope does not show this 10Vpp gain/lose when connecting the FG trigger port to scope port 4.
Hmm, I wonder where the difference comes from. These scopes should have very similar port impedances and capacitances.  Maybe their internal grounding is different.  It's worth investigating but that's for another time.
   
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Re: Smudge proposed NMR experiment replication. « Reply #131 on: 2020-07-03, 09:24:59 »

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Ok, update seen, i will make that TG/SA diagram/ movie tonight

Typing this on my iphone and 4G as now also the proxy does not work

Tried severall but none worked, not even on google etc.

I hope peter can take a look soon

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #132 on: 2020-07-03, 10:02:50 »

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Quote from: Itsu on 2020-07-03, 09:24:59
...now also the proxy does not work
I sent you 2 new ones by PM
   
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Re: Smudge proposed NMR experiment replication. « Reply #133 on: 2020-07-03, 11:55:35 »

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Thanks,   i am back in using the UK proxy, but its slow and unreliabe.

Still locked out (timing out) of OUR.com when using no proxy while all other internet traffic is working ok.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #134 on: 2020-07-03, 15:18:09 »

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Hi Itsu,
On my Magnetic Delay Transformer thread you made a twisted wire balun as reported here
https://www.overunityresearch.com/index.php?topic=3847.msg78156#msg78156
This should provide the wanted unbalanced to balanced input for the pancake coils.

Smudge
   
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Re: Smudge proposed NMR experiment replication. « Reply #135 on: 2020-07-03, 16:17:04 »

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Thanks Smudge,  i still have it somewhere, and it has galvanic isolation  O0

I will do some testing with it too.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #136 on: 2020-07-03, 21:17:31 »

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Quote from: verpies on 2020-07-02, 22:48:37
Yes, but the ones I found were much bigger.  Does yours transfer the synch pulse from the FG, even if it is only the edge ?
That's good news but I'd like to order a hookup schematic and a movie, please ;)
Hmm, I wonder where the difference comes from. These scopes should have very similar port impedances and capacitances.  Maybe their internal grounding is different.  It's worth investigating but that's for another time.

I tried 3 different baluns now, that small one, the one i made yesterday and the one made earlier as Smudge mentioned, but all 3 do NOT transfer the synch pulse from the FG   :(

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #137 on: 2020-07-03, 21:19:11 »

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Buy me some coffee
Can I post a % don't try it yourself yet though

So through cpanel I can turn mod security off, but it says this is very unwise for security purposes.
   
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Re: Smudge proposed NMR experiment replication. « Reply #138 on: 2020-07-03, 21:22:08 »

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Quote from: Peterae on 2020-07-03, 21:19:11
Can I post a % don't try it yourself yet though
Yes you can.  Did you tame the mod_security ?
   
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Re: Smudge proposed NMR experiment replication. « Reply #139 on: 2020-07-03, 21:23:06 »

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Video showing the resonance influence of the both coils (pancakes v toroidal coil) on first the scope when sweeping and then using the TG and SA.

I did a normalisation before the actual test by shorting the TG SA leads using a BNC female-female plug at the end of the cables.

 
The TG SA does not show any influence of the output trimmer cap on the resonance trace not in the input to output situation, nor in the output to input situation.

Guess the 50 Ohm impedances are causing this.

Diagram on how the setup was done below, video here: https://www.youtube.com/watch?v=_sZsrii2bhY

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #140 on: 2020-07-03, 21:28:01 »

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Buy me some coffee
I found a switch in cpanel to turn mod security off, trouble was that when I turned mod security back on and viewed the page my IP got banned, and I think anyone else that viewed it for the few seconds it was on the page also got banned oops, had to quickly change my IP turn mod off , go edit my post to say percentage lol.
Now how dangerous is it for the forum to run with mod security turned off I wonder.
   
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Re: Smudge proposed NMR experiment replication. « Reply #141 on: 2020-07-03, 21:28:19 »

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Quote from: Itsu on 2020-07-03, 21:17:31
I tried 3 different baluns now, that small one, the one i made yesterday and the one made earlier as Smudge mentioned, but all 3 do NOT transfer the synch pulse from the FG   :(
Even when driven through a small cap to eliminate the DC component ?
   
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Re: Smudge proposed NMR experiment replication. « Reply #142 on: 2020-07-03, 21:30:22 »

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Quote from: Peterae on 2020-07-03, 21:28:01
Now how dangerous is it for the forum to run with mod security turned off I wonder.
The are mentions of the impact of this solution on some security forums.
Google for the full text of the 406 error message and add "mod_security".

... the real solution though would be for the SMF code to properly escape the percent character, so the server does not frown upon it.
   
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Re: Smudge proposed NMR experiment replication. « Reply #143 on: 2020-07-03, 21:38:33 »

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Quote from: verpies on 2020-07-03, 21:28:19
Even when driven through a small cap to eliminate the DC component ?

Yes, for all 3 baluns, again nothing shows on the scope.
   
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Re: Smudge proposed NMR experiment replication. « Reply #144 on: 2020-07-03, 21:42:51 »

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Quote from: Itsu on 2020-07-03, 21:38:33
Yes, for all 3 baluns, again nothing shows on the scope.
Let me try on mine.
Which output jack on the Rigol FG do you use to obtain the signal to trigger the scope? The one the front panel or rear ?
   
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Re: Smudge proposed NMR experiment replication. « Reply #145 on: 2020-07-03, 21:48:34 »

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Its the one on the back for CH2
   
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Re: Smudge proposed NMR experiment replication. « Reply #146 on: 2020-07-03, 23:59:12 »

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Quote from: Itsu on 2020-07-03, 21:48:34
Its the one on the back for CH2
With my 1:1 telephone balun, the signal from the Trig output on the rear panel of the FG transfers as a 10ms, 3V voltage pulse on the secondary. This pulse coincides with the edge of the 1Hz square wave from the FG's Trig output.
The inductance of its open primary is 200mH.  Its core is a toroidal ferrite 20mm O.D.  Its windings do not touch (they are 5mm apart).

With the Ethernet balun, the edge of a 1Hz square wave appears as a 1µS and 3V pulse on the secondary, so you cannot see it with a slow timebase*.

P.S.
The Trig output of the FG should be protected with two back to back 5V zener diodes connected in series. These diodes short the FG's Trig output to protect it from balun's flyback voltage when its secondary is not loaded. If the secondary is always loaded then these diodes are not needed. Because of this I keep mine loaded with 1kΩ resistor (and 50Ω resistor with other signal sources)


* Some scopes cannot trigger on short pulses when their timebase is slow and the sample rate is low.
Better scopes, that have dedicated Trig inputs, can do it because they have a hardware edge detector at these inputs ...and do not depend on the sampling subsystem to capture the triggering pulse.
   
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Re: Smudge proposed NMR experiment replication. « Reply #147 on: 2020-07-04, 02:09:45 »

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If your scope cannot trigger on short pulses with slow time bases, then you can try this passive pulse stretcher.



  • Setting the scope probe to 10x is important so the probe does not drain the cap too quickly.
  • The Schottky diode D1 increases the amplitude of the stretched pulse. (this can be a small-signal Schottky diode)
  • The Zener diode D2 terminates the stretched pulse earlier (optional).

...but eventually consider making an active trigger-pulse stretcher for your scope with a flip flop, e.g. made with 74HC02 chip (or a faster one). Its disadvantage is that it needs a 3V-5V power supply on the secondary side, though.
« Last Edit: 2020-07-04, 10:38:49 by verpies »
   
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Re: Smudge proposed NMR experiment replication. « Reply #148 on: 2020-07-04, 09:53:18 »

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Quote from: verpies on 2020-07-03, 23:59:12
With my 1:1 telephone balun, the signal from the Trig output on the rear panel of the FG transfers as a 10ms, 3V voltage pulse on the secondary. This pulse coincides with the edge of the 1Hz square wave from the FG's Trig output.
The inductance of its open primary is 200mH.  Its core is a toroidal ferrite 20mm O.D.  Its windings do not touch (they are 5mm apart).

With the Ethernet balun, the edge of a 1Hz square wave appears as a 1µS and 3V pulse on the secondary, so you cannot see it with a slow timebase*.

P.S.
The Trig output of the FG should be protected with two back to back 5V zener diodes connected in series. These diodes short the FG's Trig output to protect it from balun's flyback voltage when its secondary is not loaded. If the secondary is always loaded then these diodes are not needed. Because of this I keep mine loaded with 1kΩ resistor (and 50Ω resistor with other signal sources)


* Some scopes cannot trigger on short pulses when their timebase is slow and the sample rate is low.
Better scopes, that have dedicated Trig inputs, can do it because they have a hardware edge detector at these inputs ...and do not depend on the sampling subsystem to capture the triggering pulse.

Ok,   i redid the synch pulse testing and i see its there, but indeed not visible with the normal timebase.
With the small balun i have a 3V 1.6us pulse on the secondary.
The Smudge balun is >3V at 20us even

Itsu
« Last Edit: 2020-07-04, 12:54:03 by Itsu »
   
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Re: Smudge proposed NMR experiment replication. « Reply #149 on: 2020-07-04, 12:13:11 »

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Ok, so what would be the preferred balun for the NMR input setup, the small one or the large Smudge one?
Both galvanically isolate, but does the small one also change from balanced to unbalanced?
   
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