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Author Topic: Itsu's workbench / placeholder.  (Read 47776 times)
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Yes Itsu, the scope shows 10Hz even if it's not the exact frequency.  My earlier post I was at a lower frequency but then I reduced the off time to get more sample for better averaging so that increased the frequency to above 30Hz. I explained that in my video.

Here's another test done to get a better averaging. CVR1 is 1 Ohm and CVR2 is 0.1 Ohm and went back to C1 being 100kuf

https://youtu.be/NbK5V93uOBI

Regards
Luc
   

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How does it respond to an axial (perpendicular) DC magnetic field from 300mT to 750mT when zoomed at 45.3MHz-45.7Mhz with a low VBW ?

P.S.
Please sketch the "parallel mode" before someone asks....


Manipulating 2 ceramic magnets around the toroid has a huge influence when zoomed in at 45.3MHz-45.7Mhz and low VBW
in that it is impossible to get a stable view.

Going back to 40 - 50Mhz even is hard as approaching the toroid with 1 magnet deepens the dip and moves it up frequency
(47Mhz) untill it flattens out again when touching the toroid.

In this situation (magnets attached to the toroid) even pointing to the toroid with my finger makes it deepen the dip
and moving it up frequency,  so very unstable.


Need to do some testing to find a stable view.


Itsu
   

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Buy me some coffee
What was the FG setting (T and PW)? It looks to me like about a 300us PW.

FG is set at 6V/PP,at 50Hz,with 5% duty cycle.
A diode is also used on the positive side of the FG,so as only the forward 3v(minus diode drop) triggers the transistor.


Brad


---------------------------
Never let your schooling get in the way of your education.
   

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Going back to 40 - 50Mhz even is hard as approaching the toroid with 1 magnet deepens the dip and moves it up frequency
(47Mhz)
That does not surprise me much because the external perpendicular field should decrease the effective permeability of the core.
The frequency upshift can be dealt with by adding a cap or an extra turn. In the end, the operation should be in a magnet sandwich anyway.

until it flattens out again when touching the toroid.
What do you mean?  The dip disappears completely ?

In this situation (magnets attached to the toroid) even pointing to the toroid with my finger makes it deepen the dip
and moving it up frequency,  so very unstable.
Now, the finger worries me because it cannot affect the core's permeability. It can affect the winding capaciively and we really do not want that.
   

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That does not surprise me much because the external perpendicular field should decrease the effective permeability of the core.
The frequency upshift can be dealt with by adding a cap or an extra turn. In the end, the operation should be in a magnet sandwich anyway.
What do you mean?  The dip disappears completely ?
Now, the finger worries me because it cannot affect the core's permeability. It can affect the winding capaciively and we really do not want that.




Quote
What do you mean?  The dip disappears completely ?

no, it does not disappear, it comes back from the deeper dip during magnet approach to the normal (no magnet) dip state


Quote
Now, the finger worries me because it cannot affect the core's permeability. It can affect the winding capaciively and we really do not want that.


I think the finger pointing with magnets attached (deeper dip) is the same as the deeper dip when approaching with
the magnet as i also have my finger/hand close,  so yes i think too that its (deeper dip) caused by some capacitance
effect instead of caused by the magnetic field.

I will see if i can approach the magnet using a wooden stick or so.

Itsu
   

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Yes Itsu, the scope shows 10Hz even if it's not the exact frequency.  My earlier post I was at a lower frequency but then I reduced the off time to get more sample for better averaging so that increased the frequency to above 30Hz. I explained that in my video.

Here's another test done to get a better averaging. CVR1 is 1 Ohm and CVR2 is 0.1 Ohm and went back to C1 being 100kuf

https://youtu.be/NbK5V93uOBI

Regards
Luc


Thanks Luc,   coming close.

could you please keep a DMM (in current mode) next to csr1?
It will give the correct average input current and it should compare with csr1.
As long as those 2 are not the same, there is something wrong with csr1 or how you (scope) measure it.

Itsu
   
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Thanks Luc,   coming close.

could you please keep a DMM (in current mode) next to csr1?
It will give the correct average input current and it should compare with csr1.
As long as those 2 are not the same, there is something wrong with csr1 or how you (scope) measure it.

Itsu

Hi Itsu,

Eventually I was able to get both CSR's to average using the last test setup but only by changing the circuit frequency down to 20Hz or up to 40Hz. However, at 30Hz it does what I demonstrated in my last video.
It's like the scope data only works well with even frequencies :-\
Anyways, looks like averaging is possible to achieve if you play around with the measuring and circuit conditions.
Something new learned.

BTW, I noticed you're also working on tests that involve magnets and coils?
I'm asking because I have an ferrite toroid coil I wound and pulse that when a ferrite magnet of a certain size is positioned at a certain location the input power goes down and the inductive discharge (flyback) power goes up. Don't quite understand why the input power goes down because usually a magnet will lower the inductance of a ferrite coil which would cause more current draw ???
Is that something you may be interested in seeing in your topic or should I start another topic?

Regards
Luc
   

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It's not as complicated as it may seem...
Poynt99,

here some scopeshots of my 2N3055 transistor setup
Coil is 2.7mH @ 2.6 Ohm

screenshots show Collector / emitter signals (single and multiple) and FG input (base / collector) signals (single and multiple)

Basically 86Hz with 5% on time.


Itsu

Thanks Itsu.
   

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It's not as complicated as it may seem...
Zooming in on the bottom part of the transistor Q1 on time collector signal.
The between horizontal cursors part is the base voltage (1V) plus 0.6V  (1.6V).

What did F6FLT say:


That bottom part is less then the "base voltage+0.6v", so "then the pulses are rectified by the base-collector
junction and the mean DC current goes through R7-L1-R6-R5 and can add up in R2".
(R7, R6 and R5 were some dummy 0.1 csr resistors for current measurements in the simulation, so are not really existing).

So how can we translate this bottom 1.6V rectified base-collector part to an amount of current adding up in csr2?  :o


Itsu

Although there is a fwd bias of the b-c junction during the ON time, there is negligible contribution of current from the base, so I think it can mostly be ignored.
   

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It's not as complicated as it may seem...
FG is set at 6V/PP,at 50Hz,with 5% duty cycle.
A diode is also used on the positive side of the FG,so as only the forward 3v(minus diode drop) triggers the transistor.


Brad

Can you confirm this by looking at the scope shot? Again, I see a pulse width of about 320us or so. At your stated 50Hz with a 5% duty cycle, that translates to a pulse width of 1ms, which is 3x longer than what the scope shot indicates.
   

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It's not as complicated as it may seem...
Hi Itsu,

Eventually I was able to get both CSR's to average using the last test setup but only by changing the circuit frequency down to 20Hz or up to 40Hz. However, at 30Hz it does what I demonstrated in my last video.
It's like the scope data only works well with even frequencies :-\
Anyways, looks like averaging is possible to achieve if you play around with the measuring and circuit conditions.
Something new learned.
Luc, could you please clarify the above? Are you saying that with certain settings the two csr avg currents do in fact equal?
   

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Hi Itsu,

Eventually I was able to get both CSR's to average using the last test setup but only by changing the circuit frequency down to 20Hz or up to 40Hz. However, at 30Hz it does what I demonstrated in my last video.
It's like the scope data only works well with even frequencies :-\
Anyways, looks like averaging is possible to achieve if you play around with the measuring and circuit conditions.
Something new learned.

BTW, I noticed you're also working on tests that involve magnets and coils?
I'm asking because I have an ferrite toroid coil I wound and pulse that when a ferrite magnet of a certain size is positioned at a certain location the input power goes down and the inductive discharge (flyback) power goes up. Don't quite understand why the input power goes down because usually a magnet will lower the inductance of a ferrite coil which would cause more current draw ???
Is that something you may be interested in seeing in your topic or should I start another topic?

Regards
Luc

Hi Luc,

ok good to hear that you also managed to get the csr currents averaged evenly.

I know that measurements are sometimes very cumbersome and sometimes very easy, especially when your scope
is not cooperating (it probably does what it suppose to do, but we interpret it wrongly).



I do work with verpies and others on some 45Mhz NMR (iron) experiments using a iron powdered toroid which also involve
the use of magnets.

But hearing your experiments involve ferrite i don't think it is similar, so i would advice you to
open another Topic as it does sound interesting.

Regards Itsu
   

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Although there is a fwd bias of the b-c junction during the ON time, there is negligible contribution of current from the base, so I think it can mostly be ignored.

Ok,  thanks.


here a screenshot when the load was reduced from 4 powerleds to 1.

Purple is collector /  emitter voltage
blue is base / emitter voltage


Itsu
   

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It's not as complicated as it may seem...
 O0
   
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Luc, could you please clarify the above? Are you saying that with certain settings the two csr avg currents do in fact equal?

Yes, at 20Hz or 40Hz they both equal out using my last test circuit but at 30Hz CSR1 is a little less then half the average value of CSR2 using the same circuit as demonstrated in my last video.

Added: To change the frequency all I did is change the off time, increased it for a lower frequency and decreased it for a higher frequency. The on time always stayed the same.

Regards
Luc
   

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It's not as complicated as it may seem...
Thanks Luc.

Hmm, that is very interesting!

If you have an extra meter, could you place it across CSR2 in DC voltage mode, and see what the average readings are at various frequencies (and see how they compare with the scope, and with CSR1)?
   
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Thanks Luc.

Hmm, that is very interesting!

If you have an extra meter, could you place it across CSR2 in DC voltage mode, and see what the average readings are at various frequencies (and see how they compare with the scope, and with CSR1)?

Okay, I'll post a video if anything looks interesting otherwise I'll report the results.
Also, note that I added to my previous post after you read it.

Regards
Luc
   

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It's not as complicated as it may seem...
Yup, and thanks. Still very interesting!  ;)
   
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Thanks Luc.

Hmm, that is very interesting!

If you have an extra meter, could you place it across CSR2 in DC voltage mode, and see what the average readings are at various frequencies (and see how they compare with the scope, and with CSR1)?

Okay, the problem is definitely this 4 channel scope data is unreliable. It reads fine in certain pulse condition but make one small change (like pulse width) and it all goes out. However, the Fluke digital meter measured a perfectly equal average value across each CSR to any circuit pulse or frequency change even though CSR2 is ten times smaller @ 0.1 Ohms.
It's sad when a scope can't even measure the correct average value across a resister. I guess this scope model is only good for having 4 channels and looking at waves. Just forget about the data.

Here's a video if you want to see: https://youtu.be/TD6kfI3lz24

The joys of learning something new every day.
I'm done with this one.
Thanks Itsu and Poynt for the help in solving this.

Regards
Luc
   
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BTW, if interested, here's the video I recorded before making a small change (pulse width) showing both CSR average correctly. Just keep in mind CSR1 data is divided by 10.

https://youtu.be/3DChv6La7MQ
   

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It's not as complicated as it may seem...
Thanks Luc.

I might suggest you look for a way to change the range on the Fluke 289, to mV perhaps? Some meters have a 200mV range, or something similar.

It won't change what you found, but it is better for future measurements to try and maximize the range on the meter when we can, just like on the scope.
   
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Thanks Luc.

I might suggest you look for a way to change the range on the Fluke 289, to mV perhaps? Some meters have a 200mV range, or something similar.

It won't change what you found, but it is better for future measurements to try and maximize the range on the meter when we can, just like on the scope.

Thanks Poynt,

The meter definitely has a 200mv range but I thought it would look better not having so many digits changing on the display. A kept it simple thing if it proves the point.
I agree, it can be used to measure very accurately and is the instrument used the pi filter you recommended me to built some 15 years ago (seen in my videos) to accurately measure power in a DC pulsed circuit. It's never fail me.

Regards
Luc
   

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It's not as complicated as it may seem...
I understand. ;)

It's just that the picky/ocd techie guys (like myself) get all squeamish when they see so few significant digits in a measurement, especially when it can be so easily remedied!

And btw, I don't think your scope is in any worse shape than anyone else's, there just might be some weird idiosyncrasy we have yet to discover with them. Let's wait and see what Itsu and Brad report on their tests with the meter on CSR2.

Glad to hear the input meter and filtering setup is still working for you.
   

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DMM across csr2 and csr1 compared to my el cheapo DMM measuring current in the 12V supply lead.
They are in very close agreement  :)

Video here:   https://www.youtube.com/watch?v=ZPS5ZtxStF0

Itsu
   

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no, it does not disappear, it comes back from the deeper dip during magnet approach to the normal (no magnet) dip state



I think the finger pointing with magnets attached (deeper dip) is the same as the deeper dip when approaching with
the magnet as i also have my finger/hand close,  so yes i think too that its (deeper dip) caused by some capacitance
effect instead of caused by the magnetic field.

I will see if i can approach the magnet using a wooden stick or so.

Itsu



Here a video of the 40 - 50Mhz sweep with the matching dip.
See how sensitive the dip is to movement of the hand nearby.

It is hard this way to look for an even smaller dip when narrowing the frequency sweep range.

Below a drawing on how the SA is set up.

Video here: https://www.youtube.com/watch?v=lmMmS-SVrHs

I was looking into the "trigger in" backpanel plug, but there is very little mentioned in the users guide.
So i doubt it can be used for eleborate sequencing.


Itsu
   
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