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2020-08-09, 18:51:33
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Author Topic: Smudge proposed NMR experiment replication.  (Read 7604 times)

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Itsu,

When it is convenient for you, I'm curious if you get any output from your toroid coil when positioned properly in between the driven bucking flat coils when using just two scope probes for measurement?  IOW, no grounds connected to the toroid coil so the two scope probes would then be taking a differential measurement of any output voltage across the toroidal coil.

I see no output in my setup when there is no ground reference for the solenoid coil no matter what the position of the coil in relation to the flat coils!

Regards,
Pm

Edit: The only output is an equal voltage on both coil leads but this is from the E Field of the flat coils and is not differential between the coil leads.

PM,

i did some differential probe measurements on the toroidal coil earlier in this thread when still using the normal (not litz) pancake coils, see:
https://www.overunityresearch.com/index.php?topic=3924.msg82752#msg82752

So there was output.

I will try again with the new litz wire pancakes, but it seems there is some problem with them as can be seen by the VNA outputs above.


Itsu
   
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PM,

i did some differential probe measurements on the toroidal coil earlier in this thread when still using the normal (not litz) pancake coils, see:
https://www.overunityresearch.com/index.php?topic=3924.msg82752#msg82752

So there was output.

I will try again with the new litz wire pancakes, but it seems there is some problem with them as can be seen by the VNA outputs above.


Itsu

Itsu,

OK, thanks for pointing out your previous test.  O0  I must be doing something wrong here!

Regards,
Pm
   

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PM,

here my new 2 litz wire pancakes (front and rear) with in between the water tube with toroidal coil.
Input on the left from FG (resonance) in the pancakes (series bucking), ouput toroidal coil on the right using differential probes.

Output is 100pF trimmer cap and 600K resistor parallel to coil tuned for max.


Screenshot shows the red differential output.

By the way, the (red) data in the bottom box (Value, Mean, Min etc) can that be removed so to keep only Value?

Itsu 
   
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PM,

here my new 2 litz wire pancakes (front and rear) with in between the water tube with toroidal coil.
Input on the left from FG (resonance) in the pancakes (series bucking), ouput toroidal coil on the right using differential probes.

Output is 100pF trimmer cap and 600K resistor parallel to coil tuned for max.


Screenshot shows the red differential output.

By the way, the (red) data in the bottom box (Value, Mean, Min etc) can that be removed so to keep only Value?

Itsu
Itsu,

OK, thanks for posting that result.   

On the Math measurement at the bottom of your window, you have "Statistics" turned on.  To change this, press the 'Measure' button on the front panel and then the 'More' button on the screen, and "Statistics" will be the top choice.  Simply turn it off and will then only show the main parameter of your measurement. 

I notice you have the peak-to-peak measurement selected but you can choose the rms function if you wish.  Also, a trick you can use if you have say like in this case peak-to-peak selected and you want to read rms but don't wish to change the Math, again press "measure" on the front panel and then "add measurement" on the screen.  Even though you may already have 4 measurements used, you can still select and one of the channels and select "snapshot" and you will have all the parameters showing on the screen for that channel.  I know I'm probably preaching to the choir but just in case you were not aware of this!

Regards,
Pm
   

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Made some measurements and included some in 1 screenshot, so i have 4 screenshots total.
Yup, they are not identical. Not even close  :'(
Most likely it is caused by a short, or varying CIT, or imprecise dimensions.

How to fix it? Unfortunately you have to rewind but this time put 1mm nylon fishing line between the turns, as a spacer.
This will widen the coil, stabilize the CIT as well as decrease it, so the coil's self-resonance frequency will go up. The nylon fishing line can be removed later to decrease dielectric losses and increase Q (most glues don't stick to nylon)

A coil former with a rectangular groove tailored to fit the Litz wire and the spacer (fishing line) helps immensely.  The groove helps to squeeze the turns and maintain the precise inter-turn spacing as well as the I.D. and O.D of the pancake.  This is how I was able to obtain two coils that are so similar.
I put a double sticky tape on the bottom of my groove and used small drops of low-viscosity cyanoacrlylate from an insulin syringe to secure the wires near their crossings.  The syringe and Push Tool makes this process almost enjoyable.
   

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Itsu,

OK, thanks for posting that result.   

On the Math measurement at the bottom of your window, you have "Statistics" turned on.  To change this, press the 'Measure' button on the front panel and then the 'More' button on the screen, and "Statistics" will be the top choice.  Simply turn it off and will then only show the main parameter of your measurement. 

I notice you have the peak-to-peak measurement selected but you can choose the rms function if you wish.  Also, a trick you can use if you have say like in this case peak-to-peak selected and you want to read rms but don't wish to change the Math, again press "measure" on the front panel and then "add measurement" on the screen.  Even though you may already have 4 measurements used, you can still select and one of the channels and select "snapshot" and you will have all the parameters showing on the screen for that channel.  I know I'm probably preaching to the choir but just in case you were not aware of this!

Regards,
Pm

Thanks PM,


that statistics off worked, but it keeps the box though which is now empty for the most part.
But it looks less distractive. O0


Itsu
   

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Yup, they are not identical. Not even close  :'(
Most likely it is caused by a short, or varying CIT, or imprecise dimensions.

How to fix it? Unfortunately you have to rewind but this time put 1mm nylon fishing line between the turns, as a spacer.
This will widen the coil, stabilize the CIT as well as decrease it, so the coil's self-resonance frequency will go up. The nylon fishing line can be removed later to decrease dielectric losses and increase Q (most glues don't stick to nylon)

A coil former with a rectangular groove tailored to fit the Litz wire and the spacer (fishing line) helps immensely.  The groove helps to squeeze the turns and maintain the precise inter-turn spacing as well as the I.D. and O.D of the pancake.  This is how I was able to obtain two coils that are so similar.
I put a double sticky tape on the bottom of my groove and used small drops of low-viscosity cyanoacrlylate from an insulin syringe to secure the wires near their crossings.  The syringe and Push Tool makes this process almost enjoyable.


Yes, i noticed the differences in the plots which is funny (not) as the LCR meter shows almost identical inductances.


I also noticed that the super glue i used caused the litz wire (without cloth) to thicken (and harden), so it looks like it somehow reacts with the litz wire coating or so, perhaps indeed causing a short in the end.

Ok, back to the drawing board and get out my fishing gear.


Itsu
   

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Input on the left from FG (resonance) in the pancakes (series bucking), ouput toroidal coil on the right using differential probes.
For posterity:  Ideally the amplitude from the toroidal coil should be zero, when not in NMR.

Output is 100pF trimmer cap and 600K resistor parallel to coil tuned for max.
How does that compare to the amplitude from the 1-turn sensing coil on that 110mm gray sewer pipe ?

I cannot compare them directly because this one has a different output circuit and different probing.
For comparison, I would prefer both to be without the cap at the output - only the 600K resistor.
   

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For posterity:  Ideally the amplitude from the toroidal coil should be zero, when not in NMR.
How does that compare to the amplitude from the 1-turn sensing coil on that 110mm gray sewer pipe ?

I cannot compare them directly because this one has a different output circuit and different probing.
For comparison, I would prefer both to be without the cap at the output - only the 600K resistor.

To compare you mean not using the i-probe, but both a voltage probe and both the coil/loop terminated with the 600K resistor.

   

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To compare you mean not using the i-probe, but both a voltage probe and both the coil/loop terminated with the 600K resistor.
I think for Partzman the voltage amplitude measurement would be more meaningful (with slight loading by e.g the 600K resistor)
I like the i-probe measurements better, but I have already seen a lot of them.

   

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I have measured the H-field amplitude by a 10mm loop* in 3 orientations between coaxial and parallel pancake coils (weave1, spaced 23mm) connected in parallel and brute-force fed from a a FG+PA without any matching circuits.

1) Radial: 29mA
2) Circumferential: 108µA
3) Axial
   a) Near front coil: 2mA
   b) Between coils: 5µA
   c) Near rear coil: 2mA

This is the textbook field orientation predicted in Smudge's simulation.
All measurements were made at the 50mm radius and (i.e. exactly between the windings of the front and rear coils) and at the midpoint between pancake planes.

P.S.
When the coils were connected in series, these measurements were all over the place.

* Home-made AC H-field sensor constructed from a 3mm coaxial cable, which has Litzed copper center conductor and Litzed copper braid.
   

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Quote
P.S.
When the coils were connected in series, these measurements were all over the place.



So what does that mean?    Is the bucking series configuration to sensitive to get it right/stable?

If so, why was this then the first option?


Itsu

   

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So what does that mean?    Is the bucking series configuration to sensitive to get it right/stable?
It creates different electric potentials at the front & rear pancakes.  These potentials distort measurements and create crosstalk.

If so, why was this then the first option?
Because series connection does not have a problem keeping the current equal in both pancakes.  With parallel connection extra care must be taken to keep the coils' params the same and even the cable length after the Tee matters.
Also, it is impossible to foresee every engineering difficulty.  The bench is the ultimate proof-reader.
« Last Edit: 2020-07-30, 21:15:26 by verpies »
   

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I think for Partzman the voltage amplitude measurement would be more meaningful (with slight loading by e.g the 600K resistor)
I like the i-probe measurements better, but I have already seen a lot of them.

Not sure PM is really involved in this specific setup, but below screenshots show the new pancake coils at 16mm apart in series bucking with:
1st the toriodal coil loaded with 690K
2th the single loop loaded with 690K.

Not much difference between them, so PM his statement that the toroidal coil acts like a single turn comes thru.

Itsu
   

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Not much difference between them, so PM his statement that the toroidal coil acts like a single turn comes thru.
Ok, so it is verified. 
I also have a problem with this circumferential induction when I do not use the special winding to prevent it, but I can find an axial position* between the pancakes where it crosses zero amplitude.
If my pancakes are unbalanced, e.g. by different cables in the parallel connection, then this "zero" becomes illusive for me , too.

* axial position of the big 1-turn sensing loop or a toroidal coil without the anti-circumferential induction winding. Always coaxial and parallel to the planes of the pancakes.
   

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I put up my old (non litz) pancake coils with the toroidal coil inbetween loaded with 690K.

These old pancake coils are connected parallel and the voltage in resonance (7Mhz) measured across the 690K was:

Parallel 1  20Vpp
Parallel 2 104Vpp


So in this parallel configuration with the old coils we have strong crosstalk.
   

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So in this parallel configuration with the old coils we have strong crosstalk.
Of course, these coils are not symmetrical center-to-periphery and the current flowing through the CIT creates* a magnetic field HIT, which distorts the desirable H-field.  The magnetic field must be very symmetrical in order to cancel at the middle (between the pancake coils).

In other words, these old coils have a "hot end" and the following quote from Smudge no longer applies:

Then my E field or displacement current arrows would have alternate directions and their H fields would cancel at distances from the surface greater than the turn spacings. 
Clearly this would almost eliminate that HIT field at the toroidal coil.


* It also creates an E-field wrt ground, which is picked up by scope probes.
   

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Right,  so it will be pointless to use this setup to hunt for NMR as the crosstalk would completely "cover" the possible NMR reaction.


The problem is that your new proposed litz wire coil in scheme weave 1 with the 1mm fishing line inbetween would be almost impossible to make, at least i have problems envisioning how.



Would it be an alternative to use thicker litz wire (2mm) in weave 1 scheme and losing 2 turns (8 instead of 10) and still cover the toroidal coil and be in the 4.2Mhz resonance range?



 
   

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Right,  so it will be pointless to use this setup to hunt for NMR as the crosstalk would completely "cover" the possible NMR reaction.
I think so, but I in my opinion, Smudge would like to see you try anyway because I can bet that his expectation is that with this "filling factor" the effect will be much stronger than usual and it will overwhelm the crosstalk. Right Smudge ?

Would it be an alternative to use thicker litz wire (2mm) in weave 1 scheme and losing 2 turns (8 instead of 10) and still cover the toroidal coil and be in the 4.2Mhz resonance range?
The problem with that is that with a larger wire diameter, the surface area that makes up CIT increases, and that more than compensates for the decreased inductance of fewer turns.
IMO better than a thicker wire, would be a 1mm wire with an integrated spacer (e.g. the silk braid).

The problem is that your new proposed litz wire coil in scheme weave 1 with the 1mm fishing line inbetween would be almost impossible to make, at least i have problems envisioning how.
See the diagram below. The spacers are denoted in green color. Notice, that they do not participate in the wire crossings. If you make them out of non-stick plastic (e.g. Nylon or Teflon), then they can be easily removed, leaving air gaps and a high Q coil.
« Last Edit: 2020-07-31, 11:37:58 by verpies »
   

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Quote
I think so, but I in my opinion, Smudge would like to see you try anyway because I can bet that his expectation is that with this "filling factor" the effect will be much stronger than usual and it will overwhelm the crosstalk. Right Smudge ?

Ok, so what would be the preferred setup, parallel 1 (20Vpp  6.4uH) or parallel 2 (104V 16uH)?    Guess Par. 1.



Quote
The problem with that is that with a larger wire diameter, the surface area that makes up CIT increases, and that more than compensates for the decreased inductance of fewer turns.
IMO better than a thicker wire, would be a 1mm wire with an integrated spacer (the silk braid).

See the diagram below. The spacers are denoted in green color. Notice, that they do not participate in the wire crossings. If you make them out of non-stick plastic (e.g. Nylon or Teflon), then they can be easily removed, leaving air gaps and a high Q coil.


Would love to see that diagram.


Itsu
   
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I think so, but I in my opinion, Smudge would like to see you try anyway because I can bet that his expectation is that with this "filling factor" the effect will be much stronger than usual and it will overwhelm the crosstalk. Right Smudge ?

I was hoping that the NMR frequency could be found, perhaps as just a small dip or peak (associated with the presence of the water, i.e. only there when the water is there)  superimposed on to the crosstalk.  Then you can concentrate on just that frequency, no need for wide band sweeps and all the problems with that.  At the fixed frequency you can do all sorts of things to null out the crosstalk without having to dismantle, modify and rebuild.  Without the water present play around with some external nulling feedback of some sort until you get near zero output.  Then add water.

Smudge
   

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Ok, so what would be the preferred setup, parallel 1 (20Vpp  6.4uH) or parallel 2 (104V 16uH)?    Guess Par. 1.
Yes, the configuration with the smaller inductance is the one with the opposing magnetic fields.
Notice, that with this configuration, as the coils get farther apart, the inductance increases.

Would love to see that diagram.
I re-attached it to the previous message.
   

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I was hoping that the NMR frequency could be found, perhaps as just a small dip or peak (associated with the presence of the water, i.e. only there when the water is there)  superimposed on to the crosstalk.  Then you can concentrate on just that frequency, no need for wide band sweeps and all the problems with that.  At the fixed frequency you can do all sorts of things to null out the crosstalk without having to dismantle, modify and rebuild.  Without the water present play around with some external nulling feedback of some sort until you get near zero output.  Then add water.

Smudge

Smudge,

thanks, i see what you mean,   i will use the old pancakes in parallel mode for now to hunt for a small dip or peak superimposed on to the crosstalk.


Itsu
   

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Yes, the configuration with the smaller inductance is the one with the opposing magnetic fields.
Notice, that with this configuration, as the coils get farther apart, the inductance increases.
I re-attached it to the previous message.


OK,  seen it,   so this would be the finer cut and paste work.  O0
   

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@Smudge

Let's consider two 50mm average radius pancake coils (connected in parallel) and a 10mm 1-turn sensor loop placed between these coils, as depicted on the diagram below in orange color?
When the plane of the small orange loop is perpendicular to the blue line and at a distance of 50mm from the red axis, this loop is the most sensitive to the changes of the flux generated by the pancakes in the radial direction.

What phase of voltage do you expect between the input to the pancakes and the voltage induced across the ends of this small orange loop ?
   
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