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Author Topic: Accurate Measurements on pulsed system's harder than you think.  (Read 83342 times)

tinman

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #60 on: December 11, 2015, 10:55:44 AM »

A Circuit to study might be a good start:

Tinman, is this Circuit correct? SW1 being the manual Clip lead connection.

   Chris Sykes
       hyiq.org

Lets figure out what's going on...

No,that circuit is incorrect.

EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #61 on: December 11, 2015, 11:01:12 AM »
Then you are seeing things all wrong EMJ.

No you wont,you will see a voltage across all four components when Q1 switches on,as there is no voltage across any when the circuit is open except Q1. As you can see in both mine and TK's scope shot's,there is no voltage across the CVR or bulb when Q1 is open,and the cap disconnected. We are looking at the CVR and the bulb,and that is where the scope probe's are placed.

I ask the same of you that i have asked of others that think there is nothing to it-->post a video without the inductor,and show us how an incandescent bulb can dissipate more power with less total current flowing through it,and less power with more total current flowing through it.

You may also like to look at TK's latest scope shot's,and have a look at the total current flowing through the CVR,and voltage across the bulb with and without the cap connected in the circuit. Are you telling me that the error margin could be this big ?. And dont forget,this is TK carrying out these test,and he knows his way around power measurements.


Brad


Brad, its your circuit, you know better than me.

Removing the Inductor removes its Impedance thus changing the Circuit.

Is the Circuit correct?

   Chris Sykes
       hyiq.org

tinman

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #62 on: December 11, 2015, 11:01:26 AM »
Something is wrong with the mean calculation!

At 2 volts per division for the Yellow Trace, its not giving you the right figure.

I agree with what Verpies said:

   Chris Sykes
       hyiq.org

JOKE: Try DC Coupling.... Hahahaha

EMJ
This is where incorrect assumptions start,and i hope you either remove this claim,or correct it.
If you listen to the video,and watch the video carefully,then you will know that i have dropped the channel down 1 division so as to fit the whole wave form in the scopes screen.
So the mean value given is correct,and your red voltage calculation you added to the scope shot is incorrect.


Brad

EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #63 on: December 11, 2015, 11:02:36 AM »
No,that circuit is incorrect.

Please elaborate?

   Chris Sykes
       hyiq.org

EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #64 on: December 11, 2015, 11:07:01 AM »
EMJ
This is where incorrect assumptions start,and i hope you either remove this claim,or correct it.
If you listen to the video,and watch the video carefully,then you will know that i have dropped the channel down 1 division so as to fit the whole wave form in the scopes screen.
So the mean value given is correct,and your red voltage calculation you added to the scope shot is incorrect.


Brad

Brad, from Baseline to the indicated Trace Line is only 1.7 volts approx. Have you Changed your baseline value to +2V

   Chris Sykes
       hyiq.org

TinselKoala

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #65 on: December 11, 2015, 11:20:16 AM »
Quote
TK
Try an inductor with a core.
I think the results will be better and more evident.

P.S--forgot to ask--no power measurements mentioned on the video?.

Brad

I'm not sure we are actually measuring any true power values yet.

In your original circuit, and my no-Bedini modification, the CH1 voltage drop across the bulb doesn't represent the input voltage to the circuit. The CH2 current is the input current, certainly, and actually the CH1 voltage drop across the bulb must also represent the input current and because of that we could calculate the resistance of the bulb.
 
That is, if the input current from the one-ohm CVR is, say, 94 mA (because we have  94 mV drop across 1 ohm), and we have 3.4 Vdrop across the bulb, then since both are obviously carrying the same current, we have R = V/I  so Rbulb= 3.4V/0.094 A = 36.2 Ohms. 

So maybe now we can get the power dissipation in the bulb at that current, since Watts=I2R. So we have for example W = 36.2 x (0.098)2 = 0.347 Watt being dissipated in the bulb. This is with capacitor connected in my circuit.

With cap disconnected and using the "average" values and going through the same calculations, we have average I = 62 mA and average Vdrop = 2.06 V, so the bulb's average resistance is V/I or 2.06/0.062 = 33.2 Ohms. So the average power dissipated in the bulb is 33.2 x (0.062)2 = 0.127 Watt.

What is the conclusion we can draw from this, since the bulb is obviously brighter when the cap is disconnected? Perhaps:  Using the "average" values in the way we have been doing is not correct in the case of pulses through a bulb; OR perhaps: Our assumption about the relationship between the bulb's brightness and the "average" power _in the pulses_ is not correct. Or both.

Or maybe my math is just totally screwed.

As far as the inductor goes... it is not necessary to produce the effect. I have eliminated the inductor entirely, along with the long leads I used to connect it, and I've simply placed a 34 Ohm resistor directly on my little breadboard between the bulb and the mosfet Drain, and the effect still happens just as before. There is less spikeyness when the cap is connected but the bulb dims while the "average" current through it goes up, just as before.


TinselKoala

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #66 on: December 11, 2015, 11:26:16 AM »
EMJ
This is where incorrect assumptions start,and i hope you either remove this claim,or correct it.
If you listen to the video,and watch the video carefully,then you will know that i have dropped the channel down 1 division so as to fit the whole wave form in the scopes screen.
So the mean value given is correct,and your red voltage calculation you added to the scope shot is incorrect.


Brad

Ah, that's right. EMJ is measuring from the horizontal center graticule line, and your baseline is one division below that, so your mean values are indeed correct, and not thrown off by spikes or whatnot.

In the (nearly) full shot below we can see on the left edge where the channel baselines are positioned. They are both one full division below the centerline. The yellow marker at the screen centerline is the Trigger level marker, isn't it?

EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #67 on: December 11, 2015, 11:32:02 AM »
Ah, that's right. EMJ is measuring from the horizontal center graticule line, and your baseline is one division below that, so your mean values are indeed correct, and not thrown off by spikes or whatnot.

In the (nearly) full shot below we can see on the left edge where the channel baselines are positioned. They are both one full division below the centerline. The yellow marker at the screen centerline is the Trigger level marker, isn't it?

I don't believe this is correct, yellow channel baseline is pretty much on the horizontal center graticule line: See Image

Blue Channel Baseline is 1div below the horizontal center graticule line.

Correct me if you have changed the value of this baseline Brad.

    Chris Sykes
       hyiq.org

TinselKoala

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #68 on: December 11, 2015, 11:45:06 AM »
No, both channel baselines are one division below centerline. The Blue channel marker is overlaying the Yellow channel marker so you can't see it, and the yellow marker you do see is the Trigger level indicator, indicating Trigger on CH1 (because it is yellow) and at approx. 2 Volts above the baseline,which puts it just a hair below the screen centerline marker. (See the exact trigger level on the bottom right of the screenshot I've posted.)

tinman

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #69 on: December 11, 2015, 11:57:08 AM »
I don't believe this is correct, yellow channel baseline is pretty much on the horizontal center graticule line: See Image

Blue Channel Baseline is 1div below the horizontal center graticule line.

Correct me if you have changed the value of this baseline Brad.

    Chris Sykes
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No-the yellow marker for channel 1 is being hidden by the blue marker of channel 2. The yellow marker you see at the base line is the trigger marker,and it is yellow because i am triggering on channel 1. If i was triggering on channel 2,then that marker on the base line would be blue.


Brad

EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #70 on: December 11, 2015, 11:59:38 AM »
No, both channel baselines are one division below centerline. The Blue channel marker is overlaying the Yellow channel marker so you can't see it, and the yellow marker you do see is the Trigger level indicator, indicating Trigger on CH1 (because it is yellow) and at approx. 2 Volts above the baseline,which puts it just a hair below the screen centerline marker. (See the exact trigger level on the bottom right of the screenshot I've posted.)

TK, Ok I will take your word for it but certainly looks deceiving. Thinking about this, it is correct and Brads Mean Value is right on Ch1.

Still, this still means we only have a Potential Voltage Difference of 3.374 Volts as opposed to the 8 Volts with the Cap disconnected. Being that Power is V x I when in phase, we can see a clear difference in total power through the Components in question.

8 x 0.096 = 0.768
3.374 x 0.144 = 0.485856

   Chris Sykes
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EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #71 on: December 11, 2015, 12:13:57 PM »
No-the yellow marker for channel 1 is being hidden by the blue marker of channel 2. The yellow marker you see at the base line is the trigger marker,and it is yellow because i am triggering on channel 1. If i was triggering on channel 2,then that marker on the base line would be blue.


Brad


Yes, certainly not easy to make out from the video. Honest mistake all sorted now.

    Chris Sykes
       hyiq.org

tinman

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #72 on: December 11, 2015, 12:20:43 PM »
I'm not sure we are actually measuring any true power values yet.

In your original circuit, and my no-Bedini modification, the CH1 voltage drop across the bulb doesn't represent the input voltage to the circuit. The CH2 current is the input current, certainly, and actually the CH1 voltage drop across the bulb must also represent the input current and because of that we could calculate the resistance of the bulb.
 
That is, if the input current from the one-ohm CVR is, say, 94 mA (because we have  94 mV drop across 1 ohm), and we have 3.4 Vdrop across the bulb, then since both are obviously carrying the same current, we have R = V/I  so Rbulb= 3.4V/0.094 A = 36.2 Ohms. 

So maybe now we can get the power dissipation in the bulb at that current, since Watts=I2R. So we have for example W = 36.2 x (0.098)2 = 0.347 Watt being dissipated in the bulb. This is with capacitor connected in my circuit.

With cap disconnected and using the "average" values and going through the same calculations, we have average I = 62 mA and average Vdrop = 2.06 V, so the bulb's average resistance is V/I or 2.06/0.062 = 33.2 Ohms. So the average power dissipated in the bulb is 33.2 x (0.062)2 = 0.127 Watt.

What is the conclusion we can draw from this, since the bulb is obviously brighter when the cap is disconnected? Perhaps:  Using the "average" values in the way we have been doing is not correct in the case of pulses through a bulb; OR perhaps: Our assumption about the relationship between the bulb's brightness and the "average" power _in the pulses_ is not correct. Or both.

Or maybe my math is just totally screwed.

 have eliminated the inductor entirely, along with the long leads I used to connect it, and I've simply placed a 34 Ohm resistor directly on my little breadboard between the bulb and the mosfet Drain, and the effect still happens just as before. There is less spikeyness when the cap is connected but the bulb dims while the "average" current through it goes up, just as before.

Quote
As far as the inductor goes... it is not necessary to produce the effect.

 ;) . Indeed TK,the inductor is not needed--just a pulsed system-as the thread title says.

A little info to digest.
To obtain the 22mV across the solar panel resistor(as shown in my last video),using a DC current,i need 186mA @ 5.1v to achieve the 22mV across the solar panel resistor. This is 948mW.

@ TK
Can you place a DMM amp meter in series with the CVR and bulb,and see if that gives you the same value your CVR is giving you in current amount.
Cheers

Brad

tinman

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #73 on: December 11, 2015, 12:24:00 PM »

Yes, certainly not easy to make out from the video. Honest mistake all sorted now.

    Chris Sykes
       hyiq.org

You must have a small or bad monitor EMJ,as it looks clear to me.
Hope this shows how things really are.

Brad

EMJunkie

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Re: Accurate Measurements on pulsed system's harder than you think.
« Reply #74 on: December 11, 2015, 12:27:58 PM »
You must have a small or bad monitor EMJ,as it looks clear to me.
Hope this shows how things really are.

Brad

Hahaha 1080P compared to 240??? Max in the youtube settings is 240P

Maybe you just have better eyes than me?  :D

    Chris Sykes
       hyiq.org