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Author Topic: Using a resistor to messure power consumption of a circuit.  (Read 17361 times)

tinman

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #15 on: September 16, 2014, 03:22:08 PM »
It would be a lot easier if you could post CSV files.  Otherwise, I will have to extract the values which is possible, but somewhat time consuming.

What are CSV file's Mark?

poynt99

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #16 on: September 16, 2014, 06:58:00 PM »
Ah, sorry guys.

This particular thread is not viewable to non-registered, non-enabled readers.

MarkE

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #17 on: September 16, 2014, 11:44:58 PM »
What are CSV file's Mark?
Comma separated variables.  It is a common format that most digital scopes can export, and any spreadsheet can import.

fritz

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #18 on: September 17, 2014, 10:11:22 AM »
To keep it simple and almost precise - I would simply add a driver stage - and measure the DC power consumption of the driver-stage.

With a modern scope you can get the power directly using math function by measuring voltage on DUT and voltage on current sensing resistor.....
__BUT__ a scope is not a precise instrument - and you multiply the errors in that case - and if you derive the power from a single period - this error is multiplied by 172.000 within a second for 172kHz.
... and you can export the data using csv or whatever
- but believe me - thats lots of effort - and will never reach the precision you got with 2 cheap meters measuring DC amps and DC voltage.
rgds.


MarkE

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #19 on: September 17, 2014, 10:36:34 AM »
Some people are of the mind that a decoupling filter spoils whatever magic they think might be going on inside their circuits.  When they see that DMMs don't show OU, and neither do their scopes on the DC side they figure the problem is the filter and not their circuit.  Former prof. Steven Jones claimed 8X overunity for awhile with a Joule Thief derivative.  His results were all measurement error that the kind of filter you propose would instantly expose.

fritz

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #20 on: September 17, 2014, 10:50:03 AM »
Hi MarkE,

I didn´t propose nor mention a filter (because a proper driver stage must have one anyway;-)))

Cynical people connect the rise of OU with the availability of cheap DMMs.....

Anyway, if a setup meant to be used to measure efficiency of something hooked up to a generator - the efficiency of the generator should be part of the loop.

rgds.

MarkE

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #21 on: September 17, 2014, 11:15:59 AM »
Hi MarkE,

I didn´t propose nor mention a filter (because a proper driver stage must have one anyway;-)))

Cynical people connect the rise of OU with the availability of cheap DMMs.....

Anyway, if a setup meant to be used to measure efficiency of something hooked up to a generator - the efficiency of the generator should be part of the loop.

rgds.
The dream of something for nothing is much older than DMMs.  I suppose that having a numeric readout may may measurements seem more legitimate to some than dancing needles.

fritz

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #22 on: September 17, 2014, 11:28:53 AM »
I suppose that having a numeric readout may may measurements seem more legitimate to some than dancing needles.
Some day (1995)  I attended a conference hosted by power companies with presentations of master thesis projects of the local university.
Some guy presented a mock up to measure photovoltaic networks. Obviously his approach to measure current ended up in an almost unusable noisy signal.
2/3ds of his thesis covered the clever ways he invented to smooth and integrate this noisy signal in the digital domain.
I didn´t even dare to ask why he didn´t use low noise opamps or appropriate circuitry - because he explained to me that on measuring a signal - the last digit of the DMM jumps anyway - so there is too much noise on any signal - and thats the legitimation why his master thesis is so important. OMG.

tinman

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Re: Using a resistor to messure power consumption of a circuit.
« Reply #23 on: September 18, 2014, 07:45:02 AM »
One step at a time. The end goal is to have an onboard SG, so as to get an accurate P/in measurement-probably just a fet fed by a cap and triggered by the SG. Then we just measure the DC power flowing into the cap.