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Author Topic: Parametric Charging  (Read 36866 times)

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Hi Itsu

That is a big step up you have with that transformer,which may be the problem ?

Also,dose your FG have a function where you can set the impedance to 0 ,such as mine has?

Would be good to see what type of waveforms you have across the scope as well.

As seen in all my video's,i get very clean waveforms,and the results are very easy to see.
You should be able to get 20v across the 15kohm resistor with no problem at all--maybe some tuning is needed?,due to different components.

After testing many different transformers,i finally found another that yields the COPs i have been showing-im not sure why very few give me these results,and where others of the same type(E core ferrite)show below COP+ results.


Brad


Brad,

yes, could be the step up ratio is to much.

My Rigol FG can dial in any impedance (1 Ohm being the lowest), but i don't think it will physically change
its output impedance, it will only adjust the amplitude readout (it will always stay at 50 Ohm).

Will take some screenshots tonight.

When using 20Vpp (AC) square wave signal (with input diode), i get about 6.5V across the 15K resistor.
But this input diode messes up the signal (ringing), so i also used 10Vpp (DC) square wave without the diode
which gives much cleaner signals.

So i will be looking / testing some different (ferrite cored) transformers to see if i can obtain a
lower ratio and somewhat higher primary impedance.


Gyula,

thanks for the reminder of the 36 Ohm reactance at 28.8KHz, it should be enough then for a clean signal.
Like Brad mentioned, those flittle ferrite x-formers are unforgiveable when messing with them.


Itsu
   

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1st screenshot is voltage across the prim. in yellow, using 20Vpp AC square wave 20% duty cycle (see white trace)
and using an UF4007 diode in the red supply lead.
Notice the ringing and spikes on the yellow signal.


2th screenshot is voltage across the prim. in yellow, using 10V DC square wave 20% duty cycle (see white trace)
and using NO diode in the red supply lead.
Notice the ringing is gone and less spikes.

3th screenshot is an increased vertical signal shot of the yellow voltage signal from screenshot 2 situation

 
Itsu
« Last Edit: 2018-09-02, 18:19:38 by Itsu »
   

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I found another ferrit cored transformer:

prim.  6mH /  2 Ohm
sec.  2.5H / 30 Ohm

Using the 10V DC 20% duty cycle 28.8KHz signal without input diode.
I have a DC mA DMM in the red plus lead showing the (37.2mA rms? mean?) current going in, see picture.
(a 2th Fluke DMM across a temporary installed 1 Ohm csr shows 37mV).

The screenshot shows;

yellow: the voltage across the primary (still large spikes) 911mV rms
green:  the current from my current probe in the red FG supply lead 105mA rms
red:    the math function yellow x green presenting the average input power 20.8mW

So we see 20.8mW input.

A 3th fluke DMM shows the voltage across the 14860 Ohm resistor to be 11.2V
This represents a power out of 8.7mW indicating a cop = 0.42.

Strange is the difference  between the input current DMM (37.2mA) backed up by the temp 37mV across a 1 Ohm resistor
and the current probe input current measurement of 105mA rms.

Are the DDM's unable to accuratly display the 28.8KHz current/voltage?  It looks like it.

Using another methode of obtaining the input current (2 probes in differential setup across the temp. 1 Ohm csr)
shows a similar current signal as with the current probe, but due to the low level of signals the specific value
is hard to obtain, but i tend to believe the current probe is showing the corrent input current.

Regards Itsu
   
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Dear Ion,

Okay, I understand your take on the looping conditions.

Very briefly: For me, diacs mainly mean the gate trigger devices for triacs used for mains power control so I automatically wrote to Brad the 30-35V trigger voltage they have for such purposes. Okay on building trigger diodes with quasi programmable firing voltages: I simply do not call them diacs.  I agree that trigger diodes (like Sidac) and other bilateral switches are available in wide firing voltage ranges. These are my take on these, no offense intended. Brad asked me on your suggested regenerative circuit and I wanted to keep it short: it is your baby, you run with it. 

Thanks for recommending the Class C oscillator, I agree and I would add here the use of Class E oscillators to get high efficiency DC to AC conversion. Efficiency wise I think such oscillators in practice are in par with the DC-DC converters I already referred to in my post #63. But Brad's setup involves lower voltages than Partzman's, so careful selections are needed.  I agree that a direct DC to AC conversion can be simpler.

Gyula
   
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...
Now,here is the problem--
The current through the 15kohm resistor at 22 volts is only 1.46mA  :o


Well, you have 22V DC stored in a 2200 uF capacitor.  So there is 0.5324 Joule in it. 

What is needed is to reproduce the FG's output pulses that has a 20Vpp amplitude across 50 Ohm internal resistance (when unloaded) and the pulse ON time is about 6.7-7 usec (i.e. duty cycle is 25%),  frequency is 28.8 kHz. 
Is the 20Vpp correct when the FG output is unloaded? I mean is that what reduces to 4-5 Vpp when the transformer input is hooked up to the FG?  I take the 20Vpp from your videos, it is displayed on the FG. 

I mention these because we can take out in theory 0.5324 Watt in one second from C1, this would involve using (V2/0.5324) = 909 Ohm load resisitor and the load current would be roughly 24.2 mA.  Now for your transformer input the pulse width needs to be 'only' roughly 7 usec, so this is what is needed to consider  when thinking on whether C1 stores enough energy for looping. So taking-out the pulses from C1 should be in a balance with the looped back pulses at least for a COP=1.  I ask: Is this way of thinking correct?

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I found another ferrit cored transformer:

prim.  6mH /  2 Ohm
sec.  2.5H / 30 Ohm

Using the 10V DC 20% duty cycle 28.8KHz signal without input diode.
I have a DC mA DMM in the red plus lead showing the (37.2mA rms? mean?) current going in, see picture.
(a 2th Fluke DMM across a temporary installed 1 Ohm csr shows 37mV).

The screenshot shows;

yellow: the voltage across the primary (still large spikes) 911mV rms
green:  the current from my current probe in the red FG supply lead 105mA rms
red:    the math function yellow x green presenting the average input power 20.8mW

So we see 20.8mW input.

A 3th fluke DMM shows the voltage across the 14860 Ohm resistor to be 11.2V
This represents a power out of 8.7mW indicating a cop = 0.42.

Strange is the difference  between the input current DMM (37.2mA) backed up by the temp 37mV across a 1 Ohm resistor
and the current probe input current measurement of 105mA rms.

Are the DDM's unable to accuratly display the 28.8KHz current/voltage?  It looks like it.

Using another methode of obtaining the input current (2 probes in differential setup across the temp. 1 Ohm csr)
shows a similar current signal as with the current probe, but due to the low level of signals the specific value
is hard to obtain, but i tend to believe the current probe is showing the corrent input current.

Regards Itsu

Itsu

A few things to try.

1-try using a 10 ohm cvr,so as the signal amplitude is larger.
2-set you scope to average a high number of samples--this should clean up the  waveforms.
3-adjust input frequency to point where highest voltage is obtained across the 15kohm resistor--that is what i do.
4-with the CVR on the ground rail,you should be able to use your scope to obtain the voltage across it during the 20% on time.
This gives you your current in. You then average that current over a whole cycle. If your current probe gives you a different value,then the current probe is wrong,as we have seen many times in the past.

DMMs do a very good job at averaging out pulsed DC current,as Poynt and myself have shown many times-even at higher frequencies.


Brad


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Yes, exactly. I know this, and this is part of the procedure. There is a step that perhaps you skipped which subtracts out the CVR power.

If you wish for my help I'd like to remain focused on the procedure so that there can be an understanding of the what and why.

So you obtained a total power of 69.4mW (or is it 68.4mW?).

Can you carry out the rest of the steps in the procedure and let us know how the result compares with P(out)? I see you obtained the RMS of the input current (59.4mA), so you have the data you need.

Why is an RMS value used to calculate a pulsed DC waveform?
RMS is used for AC only,or am i wrong there?

Brad


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Dear Ion,

Okay, I understand your take on the looping conditions.

Very briefly: For me, diacs mainly mean the gate trigger devices for triacs used for mains power control so I automatically wrote to Brad the 30-35V trigger voltage they have for such purposes. Okay on building trigger diodes with quasi programmable firing voltages: I simply do not call them diacs.  I agree that trigger diodes (like Sidac) and other bilateral switches are available in wide firing voltage ranges. These are my take on these, no offense intended. Brad asked me on your suggested regenerative circuit and I wanted to keep it short: it is your baby, you run with it. 

Thanks for recommending the Class C oscillator, I agree and I would add here the use of Class E oscillators to get high efficiency DC to AC conversion. Efficiency wise I think such oscillators in practice are in par with the DC-DC converters I already referred to in my post #63. But Brad's setup involves lower voltages than Partzman's, so careful selections are needed.  I agree that a direct DC to AC conversion can be simpler.

Gyula

Dear Gyula

Sorry, I should not have used the term DIAC as a bidirectional trigger device is not needed when DC is the source. I should have used a more generic unidirectional device name.

I just happened to have a few hundred 32 V devices  on hand along with other types so loosely threw it on my drawing.

I'm not 100% happy with my testing of the trigger diode approach. Although you do get a nice damped oscillation at the tank frequency with each trigger pulse, the repetition rate is not what I had hoped for.

Class E would probably be better, as you stated.

Thanks for your input

Kind Regards


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Buy me some coffee
I found another ferrit cored transformer:

prim.  6mH /  2 Ohm
sec.  2.5H / 30 Ohm

Using the 10V DC 20% duty cycle 28.8KHz signal without input diode.
I have a DC mA DMM in the red plus lead showing the (37.2mA rms? mean?) current going in, see picture.
(a 2th Fluke DMM across a temporary installed 1 Ohm csr shows 37mV).

The screenshot shows;

yellow: the voltage across the primary (still large spikes) 911mV rms
green:  the current from my current probe in the red FG supply lead 105mA rms
red:    the math function yellow x green presenting the average input power 20.8mW

So we see 20.8mW input.

A 3th fluke DMM shows the voltage across the 14860 Ohm resistor to be 11.2V
This represents a power out of 8.7mW indicating a cop = 0.42.

Strange is the difference  between the input current DMM (37.2mA) backed up by the temp 37mV across a 1 Ohm resistor
and the current probe input current measurement of 105mA rms.

Are the DDM's unable to accuratly display the 28.8KHz current/voltage?  It looks like it.

Using another methode of obtaining the input current (2 probes in differential setup across the temp. 1 Ohm csr)
shows a similar current signal as with the current probe, but due to the low level of signals the specific value
is hard to obtain, but i tend to believe the current probe is showing the corrent input current.

Regards Itsu

Itsu

Looking at your picture,i see you are connected straight to the transformer,and have bipassed the diode ?
Your voltage trace also shows this,and it looks like the FG is clamping the flyback.

The diode is a must,and your FGs offset should be at 0 volts during the 80%off time-as per the scopeshot i provided showing the pulsed waveform from my FG.


Brad


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It's not as complicated as it may seem...
Why is an RMS value used to calculate a pulsed DC waveform?
RMS is used for AC only,or am i wrong there?

Brad

If you are measuring a voltage across a pure resistance, no matter what type of wave form, the RMS voltage across it will always allow one to calculate the real power dissipated in that resistor, or calculate the RMS current through it.

The scope traces indicate that there are reactances involved  in this circuit and therefore one can not presume a DC type measurement will produce an accurate result. How much average power would be calculated with a 2Vpp sine wave across a 10R resistor using the average of the voltage? How much would be calculated using the RMS of the voltage?

Disabuse yourself of any preconceived notions regarding pulsed DC or AC, average or RMS, and give the measurement a shot. If you don't wish to pursue this line of testing, then that's ok, just let me know. I came here only because Peter asked me to take a look and see if I could figure things out. I realize however that I was not invited by the experimenters, and therefore will gracefully bow out if asked. I don't wish to waste anyone's time, nor my own.

If results are posted from the procedure I will continue, otherwise I will gracefully leave it to your capable hands.

Cheers.
   

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If you are measuring a voltage across a pure resistance, no matter what type of wave form, the RMS voltage across it will always allow one to calculate the real power dissipated in that resistor, or calculate the RMS current through it.

The scope traces indicate that there are reactances involved  in this circuit and therefore one can not presume a DC type measurement will produce an accurate result. How much average power would be calculated with a 2Vpp sine wave across a 10R resistor using the average of the voltage? How much would be calculated using the RMS of the voltage?

Disabuse yourself of any preconceived notions regarding pulsed DC or AC, average or RMS, and give the measurement a shot. If you don't wish to pursue this line of testing, then that's ok, just let me know. I came here only because Peter asked me to take a look and see if I could figure things out. I realize however that I was not invited by the experimenters, and therefore will gracefully bow out if asked. I don't wish to waste anyone's time, nor my own.

If results are posted from the procedure I will continue, otherwise I will gracefully leave it to your capable hands.

Cheers.

Poynt,please hang around,and your time here is much valued by us all.

I will get on with your method of measuring tonight when i get home,and post my results ASAP.

One question--
Should your measuring method still produce a COP of 200%+,then what?.

Please forgive me if i seem a little stubborn here,but i remember all the testing you (and myself)did using DMMs to measure pulsed DC current and voltages,and found them to be very accurate.
But after carrying out that test with great care,and tripple checking the results,it now seems that DMMs are no good ??? .
Is this just because they too returned an OU result?

Also,if the current and voltage waveforms show an inphase relationship during the 20% on time,can this not be seen as a pure resistance?--disregarding the other 80% the cycle.

Brad
« Last Edit: 2018-09-03, 07:35:31 by TinMan »


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Poynt, yes, please stick around somewhat longer to sort this thingy out.


Brad,
 

Quote
Itsu

Looking at your picture,i see you are connected straight to the transformer,and have bipassed the diode ?
Your voltage trace also shows this,and it looks like the FG is clamping the flyback.

The diode is a must,and your FGs offset should be at 0 volts during the 80%off time-as per the scopeshot i provided showing the pulsed waveform from my FG.


I explained about this diode in my posts #125/126 above (it introduces massive ringing), but if that diode is
a must for this circuit to work then i will reinstall it.

 
Quote
1-try using a 10 ohm cvr,so as the signal amplitude is larger.
2-set you scope to average a high number of samples--this should clean up the  waveforms.
3-adjust input frequency to point where highest voltage is obtained across the 15kohm resistor--that is what i do.
4-with the CVR on the ground rail,you should be able to use your scope to obtain the voltage across it during the 20% on time.
This gives you your current in. You then average that current over a whole cycle. If your current probe gives you a different value,then the current probe is wrong,as we have seen many times in the past.

1- I want to eliminate the cvr completely as it complicates the calculations.

3- So are you hunting for resonance then?

Thanks Itsu
   

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Poynt, yes, please stick around somewhat longer to sort this thingy out.


Brad,
 




 




Thanks Itsu

Hi Itsu

Quote
I explained about this diode in my posts #125/126 above (it introduces massive ringing), but if that diode is
a must for this circuit to work then i will reinstall it.

I do not understand as to why you are getting this ringing  ???,as all my waveforms are very clean,no matter what transformer i use. Maybe it is that diode--have you tried a simple 1n4007?.

Below i have added two scope shot's,which are taken from two different circuits,using different transformers.
As you can see(as in my 3 video's),my waveforms are all quite clean,and have no ringing.

Quote
3- So are you hunting for resonance then?

In my years of tinkering,i have never found that resonance has some form of hidden magic,or a means to gain energy. So no,i am not looking for resonance. I just tune the circuit to gain the highest output for the lowest input.

 
Quote
I want to eliminate the cvr completely as it complicates the calculations.

I would keep the CVR,and get rid of the troublesome current probe.They seem to be quite unreliable when trying to measure very small currents.

But first,i would work on why your traces are so noisy


Brad


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Buy me some coffee
If you are measuring a voltage across a pure resistance, no matter what type of wave form, the RMS voltage across it will always allow one to calculate the real power dissipated in that resistor, or calculate the RMS current through it.

The scope traces indicate that there are reactances involved  in this circuit and therefore one can not presume a DC type measurement will produce an accurate result. How much average power would be calculated with a 2Vpp sine wave across a 10R resistor using the average of the voltage? How much would be calculated using the RMS of the voltage?

Disabuse yourself of any preconceived notions regarding pulsed DC or AC, average or RMS, and give the measurement a shot. If you don't wish to pursue this line of testing, then that's ok, just let me know. I came here only because Peter asked me to take a look and see if I could figure things out. I realize however that I was not invited by the experimenters, and therefore will gracefully bow out if asked. I don't wish to waste anyone's time, nor my own.

If results are posted from the procedure I will continue, otherwise I will gracefully leave it to your capable hands.

Cheers.

OK,the results following your measurement procedure Poynt

Data from the scope shot below.
Our average from the math trace is 675mW/10=67.5mW--our total corrected power in.
RMS value across the 10 ohm CVR is 765mV
Power dissipated by the CVR is 58.52mW
Current through the primary coil is 76.5mA
P/in for the primary winding is there for 67.5-58.52= 8.98mW

Is this correct Poynt?


Brad


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It's not as complicated as it may seem...
One question--
Should your measuring method still produce a COP of 200%+,then what?.
Then we look deeper to verify the results.

Quote
Please forgive me if i seem a little stubborn here,but i remember all the testing you (and myself)did using DMMs to measure pulsed DC current and voltages,and found them to be very accurate.
But after carrying out that test with great care,and tripple checking the results,it now seems that DMMs are no good ??? .
Is this just because they too returned an OU result?
For P(in) measurements, DMM's are excellent for finding the average on a signal/source that is/should be flat DC. Ainslie's circuit used a battery source for the input. The load was switched, therefore the current pulsed. So when measuring power back at the battery (the source), the voltage was a no-brainer, as it is simply the loaded battery voltage. The current on the other hand is pulsed, and this is where the DMM measurement shines above the rest, because it does an excellent job averaging the current from the fixed DC source. One simply multiplies the fixed loaded DC voltage times the measured average current, and you have the input power being delivered by the battery. In your case the source voltage is not fixed, as it is a pulsed DC output. So we have to use the tried and true method with the scope doing AVG[v(t) x i(t)]. BTW, this is an instantaneous measurement done by the scope, as it is taking many samples and performing the math on each sample across the full cycle. Doing this manually as you have been is not the same thing.

Quote
Also,if the current and voltage waveforms show an inphase relationship during the 20% on time,can this not be seen as a pure resistance?--disregarding the other 80% the cycle.
That's kinda the problem; there is other stuff happening in that wave form, and it all has to be accounted for. The best method we have available to achieve this is the one I've been asking you to use.
   

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It's not as complicated as it may seem...
OK,the results following your measurement procedure Poynt

Data from the scope shot below.
Our average from the math trace is 675mW/10=67.5mW--our total corrected power in.
RMS value across the 10 ohm CVR is 765mV
Power dissipated by the CVR is 58.52mW
Current through the primary coil is 76.5mA
P/in for the primary winding is there for 67.5-58.52= 8.98mW

Is this correct Poynt?


Brad
Your math looks correct.

This seems low, and I am assuming that the P(out) is a fair bit higher in this case.

In my experience working with the scope and this method, it is important to use a high number of cycles on the display when utilizing the "measurements" available in the scope, especially for MEAN, RMS measurements. Also, be careful with the selection of MEAN options, as there is often a "Cycle MEAN", and just "MEAN". I prefer to use just "MEAN", and have many cycles showing on the screen, at least 25 cycles. This should produce the most accurate measurement. So I would suggest you experiment with this as well, and note how or if the numbers_in_boxes changes as you vary the number of cycles on the screen.

Another important adjustment, is the samples per second, and number of points in the screen. Your screen shot indicates 500Ms/s, and 120k points. This will provide a fast screen update, but may not provide the most accurate measurement. See if you can increase the samples and points and observe the effect (if any) on the measurements.

The other potential source of error is the CVR. Even though the frequency is relatively low (~28kHz), the quick rise and fall times of the source signal will bring into effect the circuit reactances, particularly across the CVR. Because the CVR is a relatively low value of 10 Ohms, only a tiny bit of inductance in the CVR is necessary to significantly skew the resulting voltage measured across it. I strongly suggest that those pretty gold power resistors not be used as CVR's. This has been discussed many many times over the years, and several CVR options suggested, esp by TK. Because you are dealing with such low power, why not use a simple 1/2W or 1W carbon resistor? The value/tolerance is not too critical, as you can measure that accurately, and make the necessary allowance in your calculations. At least then the inductance will be at a minimum. Also, ensure that the scope probes are directly across the CVR as close to the resistor body as possible.
   
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All,

Yesterday, I was trying to use some of the other mosfets using the newly measured capacitance change data and the results were terrible.  So, I thought I would replicate my previous circuit and data in post #9 for comparison and all attempts throughout the day to replicate the performance failed with all circuit values and measurement procedures identical.  The COPs were ~.8-.9 at best.  The weather here was overcast and rainy off and on all day during these test attempts! 

This morning, all the weather has moved on and we have a bright sunny day at the moment and when running the replication test at this moment in time, the COPs with gain have returned.  Any suggestions as to why this is happening?  I might add that my lab is basically climate controlled so I believe there is no test equipment variables to deal with.  Is it possibly diurnal although I tested both day and night?  Or is the frequency close to the first odd integer frequency of 710,611 Hz as calculated with Dr. Stifflers lattice energy formula he disclosed in this video-

https://www.youtube.com/watch?v=oPikYP40NS8&t=87s

You probably won't be able to read the formula but thanks to iQuest and Mikrovolt on OU, the following is an accurate representation.

Lv=(Zo*(c/1e6)*2pi)*n

Lv - Lattice Vibration Frequency (Frequency At Which Energy Lattice Will Release Energy)
Zo - Free Space Impedance (120*PI), may be rounded to 377
  c - Speed Of Light (300M meters/sec)
  n - Every Odd Integer

Lv odd integer frequencies:
1 - 710,611        3 - 2,131,834       5 - 3,553,057       7 - 4,974,280          9 - 6,395,503      11 - 7,816,726
13 - 9,237,949   15 - 10,659,172   17 - 12,080,395   19 - 13,501,618    21 - 14,922,841   23 - 16,344,064

Any thots?

At Itsu:  What is your weather like at the time or when you attempted to replicate this circuit?

Regards,
Pm




   
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This is a follow up of sorts to my last post in regards to Dr. Stiffler's energy lattice formula in which the first odd integer calc results in 710,611Hz.  This is a test of the circuit used in my post #9 except the frequency is now 710,611Hz, C2 is changed to 2108pf to change the transfer function, and the scan is now 200ms with a sample rate of 50MS/s.

The first scope pix shows the measurements at 100ms and the second pix is the same area expanded.  The scope shot was taken with a single hi-res sample which has 16 bit vertical resolution.

The data table is also shown.

Regards,
Pm
   

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Checking my current probe seems that its in good working order, however while doing some comparing measurments,
it seems that the DMM's in DC mA mode and in DC mV mode show the MEAN (Average) current/voltage.

While the scope (my scope) uses for the math calculations x (and probably / ) the both RMS values of the signals.
When using the - or + math function it uses the mean values of the signals.
This seems to be in my TDK3000 series of scope.

So be aware, while you can display the signals in mean on your scope, the math function x  and /  will probably
take the rms value of those signals and display the result in what you set it, normally in mean.

This means that 3 methods of obtaining the current via a cvr (DC mA DMM in the supply line, DC mV DMM across the cvr and the differential probe setup CHx - CHY) all use the MEAN
values, while the Voltage x current math function uses the rms values.

Can this be right?

 
Itsu
« Last Edit: 2018-09-03, 21:23:03 by Itsu »
   

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All,

Yesterday, I was trying to use some of the other mosfets using the newly measured capacitance change data and the results were terrible.  So, I thought I would replicate my previous circuit and data in post #9 for comparison and all attempts throughout the day to replicate the performance failed with all circuit values and measurement procedures identical.  The COPs were ~.8-.9 at best.  The weather here was overcast and rainy off and on all day during these test attempts! 

This morning, all the weather has moved on and we have a bright sunny day at the moment and when running the replication test at this moment in time, the COPs with gain have returned.  Any suggestions as to why this is happening?  I might add that my lab is basically climate controlled so I believe there is no test equipment variables to deal with.  Is it possibly diurnal although I tested both day and night?  Or is the frequency close to the first odd integer frequency of 710,611 Hz as calculated with Dr. Stifflers lattice energy formula he disclosed in this video-

https://www.youtube.com/watch?v=oPikYP40NS8&t=87s

You probably won't be able to read the formula but thanks to iQuest and Mikrovolt on OU, the following is an accurate representation.

Lv=(Zo*(c/1e6)*2pi)*n

Lv - Lattice Vibration Frequency (Frequency At Which Energy Lattice Will Release Energy)
Zo - Free Space Impedance (120*PI), may be rounded to 377
  c - Speed Of Light (300M meters/sec)
  n - Every Odd Integer

Lv odd integer frequencies:
1 - 710,611        3 - 2,131,834       5 - 3,553,057       7 - 4,974,280          9 - 6,395,503      11 - 7,816,726
13 - 9,237,949   15 - 10,659,172   17 - 12,080,395   19 - 13,501,618    21 - 14,922,841   23 - 16,344,064

Any thots?

At Itsu:  What is your weather like at the time or when you attempted to replicate this circuit?

Regards,
Pm


PM,

interesting, i have seen that formula, but i understand that the jury is still out on that formula untill some math guru's
have given the OK on it.


Our weather was unusually dry and warm this summer, only untill 3 weeks ago or so it changed back to our normal
Dutch summer weather meaning humid (70%), cooler, partly clouded and some rain now and then.
It was in those last 3 weeks that i was doing the replication on your circuit.

Itsu
   

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Hi Itsu

I do not understand as to why you are getting this ringing  ???,as all my waveforms are very clean,no matter what transformer i use. Maybe it is that diode--have you tried a simple 1n4007?.

Below i have added two scope shot's,which are taken from two different circuits,using different transformers.
As you can see(as in my 3 video's),my waveforms are all quite clean,and have no ringing.

In my years of tinkering,i have never found that resonance has some form of hidden magic,or a means to gain energy. So no,i am not looking for resonance. I just tune the circuit to gain the highest output for the lowest input.

 
I would keep the CVR,and get rid of the troublesome current probe.They seem to be quite unreliable when trying to measure very small currents.

But first,i would work on why your traces are so noisy


Brad


I changed the following on my setup:

using a 10 Ohm CVR
using a 1N4007 diode in the supply line
lowering the FG frequency to a point of max. voltage across the load resistor (2.2Khz).

We have a much stable signals (also due to the lower frequency) but the 1N4007 introduces much less
ringing compared the the (better?) UF4007.

The input current seems to be 12.5mA on the DC mA DMM in the supply lead, 125mV on the DC mV DDM across
the 10 Ohm cvr, 130mV mean using 2 probes in differential mode and using math CH2 - CH3 and 31.2mA RMS using
the current probe (9.7mA mean).

The voltage across the primary is 3.64V RMS.

The power in calculated by the math function shows 50mW.

The voltage across the load resistor (14860 Ohm) is 24.64V for a power out of  40.7mW.

COP therefor is now 0.82

Itsu
   
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Checking my current probe seems that its in good working order, however while doing some comparing measurments,
it seems that the DMM's in DC mA mode and in DC mV mode show the MEAN (Average) current/voltage.

While the scope (my scope) uses for the math calculations x (and probably / ) the both RMS values of the signals.
When using the - or + math function it uses the mean values of the signals.
This seems to be in my TDK3000 series of scope.

So be aware, while you can display the signals in mean on your scope, the math function x  and /  will probably
take the rms value of those signals and display the result in what you set it, normally in mean.

This means that 3 methods of obtaining the current via a cvr (DC mA DMM in the supply line, DC mV DMM across the cvr and the differential probe setup CHx - CHY) all use the MEAN
values, while the Voltage x current math function uses the rms values.

Can this be right?

 
Itsu

Itsu,

Well, the best way to tell is to do an experiment and although I'm using my Tek MDO, your TDS should measure in the same manner.

The test setup is a signal generator set at 500kHz sine wave driving a 100 ohm 1% non-inductive resistor with the current being measured with a Tek TCP0020 current probe.  I could have used a CSR and the results would have been more accurate on the second test.

The first scope pix shows the voltage and current waveforms with very little phase difference and the resulting mean Math channel calculation.   So, we multiply the rms values and get Pin = 4.415*42.47e-3 = 187.5mw. neglecting the small phase angle.  This compares favorably with the Math channel value of 187.3w.

In the next scope pix, we've added a ~100uh inductor to create some phase shift to move the power factor off unity so we'll be forced to use cosine correction.  Therefore now the Pin = 6.118*16.64e-3*cosine(72.48) = 30.65mw.  The Math shows 28.17mw for an error of 9% which I attribute to the fact that we are in the minimum current range of 10ma for the TCP0020 probe rather than the internal math calculations of the Tek scope.

Rather than repeat here, one can look at my post #88 for an explanation of how the "mean" or average measurements are taken on complex waveforms with the current Tek scopes.

Regards,
Pm   
   
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Interesting! 
PM writes: "Yesterday, I was trying to use some of the other mosfets using the newly measured capacitance change data and the results were terrible.  So, I thought I would replicate my previous circuit and data in post #9 for comparison and all attempts throughout the day to replicate the performance failed with all circuit values and measurement procedures identical.  The COPs were ~.8-.9 at best.  The weather here was overcast and rainy off and on all day during these test attempts! 

This morning, all the weather has moved on and we have a bright sunny day at the moment and when running the replication test at this moment in time, the COPs with gain have returned.  Any suggestions as to why this is happening? "

   Air humidity is clearly suspect as the culprit.  Possibly in your lab, but possibly humidity in the air outside...
   WHY humidity might matter so much, is another question. 
I would say it is very valuable to be able to turn the effect "off", and you have evidently found one way to do this, with increased air humidity.

   

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It's not as complicated as it may seem...
Checking my current probe seems that its in good working order, however while doing some comparing measurments,
it seems that the DMM's in DC mA mode and in DC mV mode show the MEAN (Average) current/voltage.

While the scope (my scope) uses for the math calculations x (and probably / ) the both RMS values of the signals.
When using the - or + math function it uses the mean values of the signals.
This seems to be in my TDK3000 series of scope.

So be aware, while you can display the signals in mean on your scope, the math function x  and /  will probably
take the rms value of those signals and display the result in what you set it, normally in mean.

This means that 3 methods of obtaining the current via a cvr (DC mA DMM in the supply line, DC mV DMM across the cvr and the differential probe setup CHx - CHY) all use the MEAN
values, while the Voltage x current math function uses the rms values.

Can this be right?

 
Itsu

Hi Itsu.

What indications are you seeing that leads you to conclude the scope is performing any conversion (MEAN or RMS) on the v(t) x i(t) components?

When you set up the MATH channel/trace to perform CH1 x CH2 (for example), there is no processing before or after the result. You can see the result in Brad's scope shots (the purple trace), and it is just the raw output or result of the v(t) x i(t) process. When you set up a measurement on a channel/trace, then processing is performed and the result is indicated in the box labeled AVG or MEAN, or RMS etc.

In the case of the MATH trace set up for measuring power, the raw product is processed with the MEAN measurement function in order to take the instantaneous power trace and convert it to the average power.
   

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Buy me some coffee
Your math looks correct.

This seems low, and I am assuming that the P(out) is a fair bit higher in this case.

In my experience working with the scope and this method, it is important to use a high number of cycles on the display when utilizing the "measurements" available in the scope, especially for MEAN, RMS measurements. Also, be careful with the selection of MEAN options, as there is often a "Cycle MEAN", and just "MEAN". I prefer to use just "MEAN", and have many cycles showing on the screen, at least 25 cycles. This should produce the most accurate measurement. So I would suggest you experiment with this as well, and note how or if the numbers_in_boxes changes as you vary the number of cycles on the screen.

Another important adjustment, is the samples per second, and number of points in the screen. Your screen shot indicates 500Ms/s, and 120k points. This will provide a fast screen update, but may not provide the most accurate measurement. See if you can increase the samples and points and observe the effect (if any) on the measurements.

The other potential source of error is the CVR. Even though the frequency is relatively low (~28kHz), the quick rise and fall times of the source signal will bring into effect the circuit reactances, particularly across the CVR. Because the CVR is a relatively low value of 10 Ohms, only a tiny bit of inductance in the CVR is necessary to significantly skew the resulting voltage measured across it. I strongly suggest that those pretty gold power resistors not be used as CVR's. This has been discussed many many times over the years, and several CVR options suggested, esp by TK. Because you are dealing with such low power, why not use a simple 1/2W or 1W carbon resistor? The value/tolerance is not too critical, as you can measure that accurately, and make the necessary allowance in your calculations. At least then the inductance will be at a minimum. Also, ensure that the scope probes are directly across the CVR as close to the resistor body as possible.

Ok,i will up the sample rate on the screen,and give that a shot.

A few things--

This test was done on my second DUT,and the frequency is around 14.7KHz.

The resistors used on this DUT are the 1/2 watt carbon resistors..
On that note,the large gold ones were described as being carbon resistors by the seller,not the wire wound cement type,such as some of those white block ones i have,which is why i bought them-the gold ones.

I will redo the test tonight,post the results,and touch on a !hiccup! using this test method.

Brad



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