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2022-11-29, 07:21:32
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Author Topic: Smudge proposed NMR experiment replication.  (Read 74352 times)

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Yeah, i tried acetone, but it did nothing to remove the magnet wire coating.
 
   

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Buy me a beer
Try flow solder and flux, heat with a hot air gun when the two parts are together

As used with soldering SMD components.

Regards

Mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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As a general rule, the most successful person in life is the person that has the best information.
   

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I tried flux, and used a 120W soldering iron, but its not flowing / sticking, just smoking, smelling and burning.

Unfortunatly i have no heat gun to try.

Itsu
   
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Some enameled wire has high temp coating that would be almost impossible to tin in this config.

Some winding wire  like from jaycar actually act as solder flux and it would go fairly smooth.

Another thing is the so called "lead free" solder which can be less than useless for this.

Every time i buy solder advertised as 60/40 ...half the time it goes in the bin with along with an ebay refund.

Jaycar do have the right 60/40 solder if that helps.
   

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Thanks 3D,

i am using "lead free" solder since a few years and really had to adapt to it.
So it might have something to do with that too, so i will be looking for some old fashion 60/40 solder lead solder.

Itsu
   
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Hi Folks,

On flux you mean pine resin?

Here is what I mean:    https://www.amazon.co.uk/Natural-ROSIN-COLOPHONY-Incense-Solder/dp/B01N11EUFS 

Thanks,
Gyula
   

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Hi Folks,

On flux you mean pine resin?

Yes I have that in small tubs, works well normally and is non acid unlike the others. It is solid until you touch with the tip of the soldering iron.

But what I use for smd is a soler paste in a tube.

Regards

Mike 8)

Here is what I mean:    https://www.amazon.co.uk/Natural-ROSIN-COLOPHONY-Incense-Solder/dp/B01N11EUFS 

Thanks,
Gyula


---------------------------
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   
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Hi Itsu and Mike,

Okay, thanks for the answers.

Itsu,  I have often used a contact spray, TUNER 600, when I quickly  wanted a clean surface for soldering. It  dries  in  seconds,  leaving  no  residue (and the surface this spray is applied on cools down).
 Here is a data sheet on it:  http://www.dact.com/Tuner_600_data_sheet.pdf

Please note that this spray does not remove enamel from the wire, it should be removed first by other means, unfortunately. 

A possible source for TUNER 600:   https://www.soselectronic.com/products/kontakt-chemie/tuner-600-200ml-33196    At other places it tends to be more expensive.

Gyula
   

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Thanks Gyula,

i have "Kontakt 60", which is a similar contact spray i guess, but as you mentioned it will not clean off any enamel or varnish.

Itsu
   

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I was able to make some shielding around the weaved tube coil using some litz wire, see pictures

Doing same measurement as in post #659 above but using the scale as in verpies his post #664.

Screenshot 1 shows the outcome (worse seems to me) without the shield grounded.
Screenshot 2 shows the outcome with the shield grounded.

There are a lot of differences, but not any better in my opinion as the unshielded outcome in post #659


Inbetween those measurements, there was a VNA upgrade to be able to vary the transmittion level (+1dBm, -1dBm, -4dBm and -10dBm).

No idea what level i was on,  now i have set it to -1dBm so probably the 2 situations are not comparable  :(

Itsu

   

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As my shielding is asymmetrical (short side curls in, long side extends to the middle) due to avoiding the ends touching, i tried swapping over the weaved coil, so now the long extended shielding side is exposed to the transmitting loop, and the picture changes.

 
Below screenshot 1 is with flipped over coil in the same scale as my post above.
We now see a flatlining over the first 17Mhz or so on the S21 graph.

Screenshot 2 is a zoomed in shot of S21 graph.

Grounding the shield makes things worse

Itsu
   

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I folded over the long side of the shielding inside over the short side making sure they did not contact each other and taped it all around the tube.

Now measurements show an almost equal damping from both sides (S21 Gain of -62dB).

I have sandwiched the tube coil between the 2 spiral weaved coils for further maesurments

Itsu
   

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I finally was able to put all items of this setup together, see picture.

I have the 2 weaved pancake coils put in parallel bucking (4uH @ 100KHz) 2cm apart.
The tube coil also weaved measures 11uH @ 100KHz.

The tube is filled with double distilled water and the tube coil screen is grounded.

Running at 4.250MHz for now (sine wave DC) from my FG into the Amplifier which pulls 12.7V @ 1.2A (16W).

Input circuit is balun across a 10nF cap then a series trimmer cap 100pF with across it a fixed 220pF ceramic (total 320pF) to the both paralleled pancake coils.
Output circuit is a 100pF trimmer cap parallel to the tube coil to a parallel 670KOhm load resistor, see diagram.

Output measurement shown in screenshot below, yellow = voltage across the 670K resistor (11.8V rms), green = current probe in this 670K load resistor (1.7mA rms), red is math function voltage x current (2mW) .
Strange is that the voltage and current are not in phase.     Also, P=U²/R would result in 0.2mA........


I will do some tuning and adjustments to hunt for anomalies

Video here:  https://youtu.be/5IeLHGW7Qco

Regards Itsu


   

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Itsu,

That looks like a 90 degree phase between voltage and current.  The ratio of rms voltage to rms current gives a capacitive reactance of 6.9Kohms.  At your frequency that works out to a 5pF capacitance, which would be the scope probe.

Smudge
   

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Hi Smudge,

Ok, sounds plausible, the phase difference is about 84°, but why does the P=U²/R gives a 10 times lower value at 0.2mA?

Itsu
   

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Hi Itsu,

Maybe the 670K resistor isn't 670K.

Smudge
   

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Smudge, you are right, its 690K   :P
   
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Hi Itsu,

Would you check the resistance or impedance of the 690 k resistor with your LCR meter at 100 kHz? 

On your question:  why does the P=U²/R gives a 10 times lower value at 0.2mA?   Smudge meant the resistor cannot be 670 kOhm because the measured current and voltage (if we are to believe the measurements and we surely can)  shows it otherwise.  The 84° phase difference (current leads voltage) certainly indicates the resistor, together with the voltage probe is a capacitive load, as he also mentioned.

The 4.25 MHz frequency is very high for such type and many kOhm value resistors from the self inductance and capacitance point of view. 
If you have 3 pieces of 220 kOhm similar size resistors, try to connect them in series and replace the 690 Kohm single resistor and see how the phase angle, current and voltage changes if any.
OR, just omit the 690 K resistor and see the voltage and current without it. Use say two 3 cm long pieces of wire to replace the legs of the resistor, voltage probe would clip across these open wire ends and the current probe would clamp around one wire like it was for the resistor. (the load in this case would be the probe input impedance (parallel RC) as specified for that voltage probe)

Gyula
   

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Gyula,

thanks for your insights.

The used 690K resistor measures 450mH @ 100KHz, which i find hard to believe.

Concerning the "P=U²/R gives a 10 times lower value at 0.2mA?" (must be 0.2mW!!) i gather that the scope math shows the correct calculated value (2mW), and the "P=U²/R" goes wrong due to the 84° phase shift.

But if i incorperate this 84° phase shift by multiplying the 0.2mW by Cos84 i get an even worse outcome (0.02mW).

A 100 Ohm 1% induction free resistor as load gives more normal (no phase shift) results, so it must be the used 690K with its reactance that plays up.

I will do your tests later tonight.

Regards Itsu
   
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Hi Itsu,

Thanks for doing the 100 Ohm load test check.

I cannot recall the type of your LCR meter, does it have series or parallel equivalent impedance selection choice?  And in resistance mode does it use normal DC current only? 

Normally, as the frequency increases from the kHz to the MHz range, a film or metal film resistor gradually becomes increasingly reactive (mostly capacitive but even a turning point for inductive nature may happen), especially for the higher values like a few kOhm and higher.  Check a few kOhm, then say some ten kOhm and then some hundred kOhm metal film types at 100 kHz with your meter, just for fun to see this behaviour for yourself.

I think this formula P=U²/R is valid for resistances without any reactance and you can use a Z impedance instead of the R resistance if the impedance is real.

Greetings
Gyula
   
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Gyula,

thanks for your insights.

The used 690K resistor measures 450mH @ 100KHz, which i find hard to believe.

Concerning the "P=U²/R gives a 10 times lower value at 0.2mA?" (must be 0.2mW!!) i gather that the scope math shows the correct calculated value (2mW), and the "P=U²/R" goes wrong due to the 84° phase shift.

But if i incorperate this 84° phase shift by multiplying the 0.2mW by Cos84 i get an even worse outcome (0.02mW).

A 100 Ohm 1% induction free resistor as load gives more normal (no phase shift) results, so it must be the used 690K with its reactance that plays up.

I will do your tests later tonight.

Regards Itsu

Itsu,

Actually, with the scope measured rms voltage and current being 11.83v and 1.714ma respectively, to arrive at the mean output of 2.406mw would require a phase angle of arccos(2.406e-3) = 89.862 degrees.  This phase angle could be assumed from the traces.  Pout = 11.83*1.714e-3*cos(89.862) = 2.408mw.

Also, the current lead of ~90 degrees simply means the network connected between the probes is capacitive at the frequency used no matter what the indicated resistor value is.

Pm
   

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Hi Itsu,

Thanks for doing the 100 Ohm load test check.

I cannot recall the type of your LCR meter, does it have series or parallel equivalent impedance selection choice?  And in resistance mode does it use normal DC current only? 

Normally, as the frequency increases from the kHz to the MHz range, a film or metal film resistor gradually becomes increasingly reactive (mostly capacitive but even a turning point for inductive nature may happen), especially for the higher values like a few kOhm and higher.  Check a few kOhm, then say some ten kOhm and then some hundred kOhm metal film types at 100 kHz with your meter, just for fun to see this behaviour for yourself.

I think this formula P=U²/R is valid for resistances without any reactance and you can use a Z impedance instead of the R resistance if the impedance is real.

Greetings
Gyula

Gyula,

My LCR meter is an Agilent U1733C, and it does have the series/parallel selection choice.
Not sure about the resistance mode being DC current only.

Knowing the impedance of this 690K resistor @ 4.250MHz would be nice, but neither my LCR meter nor the little VNA is able to measure it somehow.

Itsu
   

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Itsu,

Actually, with the scope measured rms voltage and current being 11.83v and 1.714ma respectively, to arrive at the mean output of 2.406mw would require a phase angle of arccos(2.406e-3) = 89.862 degrees.  This phase angle could be assumed from the traces.  Pout = 11.83*1.714e-3*cos(89.862) = 2.408mw.

Also, the current lead of ~90 degrees simply means the network connected between the probes is capacitive at the frequency used no matter what the indicated resistor value is.

Pm

PM,

thanks, so the scope math shows the correct power level (2.4mW), but the problem is the P=U²/R calculation, which is only 0.2mW, and even when using the 89 or 84° phase shift does not correct this (gets worse).

Only when taking a value of 69K then it starts making sense (without the COS phi).

Anyway, i will not use the P=U²/R*COS(phase shift) for output power calculations.

Itsu   
   

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Gyula,

Quote
OR, just omit the 690 K resistor and see the voltage and current without it.
Use say two 3 cm long pieces of wire to replace the legs of the resistor, voltage probe would clip across these open wire ends and the current probe would clamp around one wire like it was for the resistor.
(the load in this case would be the probe input impedance (parallel RC) as specified for that voltage probe)



Thats what i did, and below the resulting traces, see screenshot 1
Yellow probe is specified as 3.9pF@10MOhm.


2th screenshot is with a 100 Ohm 1% induction free resistor as load.


Itsu
   
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