Quantum Energy Generator (QEG) Open Sourced (by HopeGirl)

[isim]

@TinselKoala
"The QEG people have also spoken of a Fluke current clamp something like this:
http://www.transcat.com/Catalog/productdetail.aspx?itemnum=I310S&utm_source=google&utm_medium=base&gclid=CMvG-oLi4r8CFZTm7AodxnIAug
and I have no idea about what artifacts it might introduce into a measurement. I'd sure like to own one though."
It  Bandwidth is from  dc to 1 kHz so it's does not work for 400kHz or 1Mhz!

Her an excerpt from the Manufacturer PDF on the same link:
"Output Sensitivity 10 mV/A (30 A)
                            1 mV/A (300 A)
Accuracy
(30 A range) ± 1 % of reading ± 50 mA
(300 A range) ± 1 % of reading ± 300 mA
@25 °C, Bandwidth dc to 1 kHz
Bandwidth to Meet Accuracy Specification 1 kHz
Phase Shift below 1 kHz  < 2 degrees
Resolution
                                       ± 50 mA (30 A)
                                       ± 100 mA (300 A)
Load impedance > 10 k Ω and ≤ 100 pF"

@MarkE
"The principles are good, but the specific clamps are directed at much higher frequencies than in TinselKoala's application."
Yes I know, but I had some difficulties to find good links in english.
http://www.coilcraft.com/pwrsense.cfm, a example of industrial 50kHz to 1MHz CT.
http://www.digikey.com/Web%20Export/Common/icons/datasheet.png
For the this range of frequency, the the theory is the same.
Here a link in french: http://books.google.fr/books?id=b3-SFGPYJs4C&pg=PA14&lpg=PA14&dq=th%C3%A9orie+transfo+courant+hf&source=bl&ots=R8Yh6Yx8SY&sig=gXhjzx2wvz2-4KODTSU46nNVzN0&hl=fr&sa=X&ei=JanPU_OfMfLZ0QXRu4DQBw&ved=0CDEQ6AEwAzge#v=onepage&q=th%C3%A9orie%20transfo%20courant%20hf&f=false

1) If ωc is the low cutoff frequency ωc=R/L , R must be low and L big to have a low ωc...
More, the tranfert function  is Vs/Is=  k* ( i*ω/ωc)/(1+ i*ω/ωc)     with (i=sqt(-1))
and the phase shift: phi=atn(ωc/ω), so Phi is neat zero if ωc<<ω...
(if i don't make an error...)

2) The high limit is set by the core loss...
And the phase depend mainly of  ω/ωc.

@+

[MarkE]

@TinselKoala
"The QEG people have also spoken of a Fluke current clamp something like this:
http://www.transcat.com/Catalog/productdetail.aspx?itemnum=I310S&utm_source=google&utm_medium=base&gclid=CMvG-oLi4r8CFZTm7AodxnIAug
and I have no idea about what artifacts it might introduce into a measurement. I'd sure like to own one though."
It  Bandwidth is from  dc to 1 kHz so it's does not work for 400kHz or 1Mhz!

Her an excerpt from the Manufacturer PDF on the same link:
"Output Sensitivity 10 mV/A (30 A)
                            1 mV/A (300 A)
Accuracy
(30 A range) ± 1 % of reading ± 50 mA
(300 A range) ± 1 % of reading ± 300 mA
@25 °C, Bandwidth dc to 1 kHz
Bandwidth to Meet Accuracy Specification 1 kHz
Phase Shift below 1 kHz  < 2 degrees
Resolution
                                       ± 50 mA (30 A)
                                       ± 100 mA (300 A)
Load impedance > 10 k Ω and ≤ 100 pF"

@MarkE
"The principles are good, but the specific clamps are directed at much higher frequencies than in TinselKoala's application."
Yes I know, but I had some difficulties to find good links in english.
http://www.coilcraft.com/pwrsense.cfm, a example of industrial 50kHz to 1MHz CT.
http://www.digikey.com/Web%20Export/Common/icons/datasheet.png
For the this range of frequency, the the theory is the same.
Here a link in french: http://books.google.fr/books?id=b3-SFGPYJs4C&pg=PA14&lpg=PA14&dq=th%C3%A9orie+transfo+courant+hf&source=bl&ots=R8Yh6Yx8SY&sig=gXhjzx2wvz2-4KODTSU46nNVzN0&hl=fr&sa=X&ei=JanPU_OfMfLZ0QXRu4DQBw&ved=0CDEQ6AEwAzge#v=onepage&q=th%C3%A9orie%20transfo%20courant%20hf&f=false

1) If ωc is the low cutoff frequency ωc=R/L , R must be low and L big to have a low ωc...
More, the tranfert function  is Vs/Is=  k* ( i*ω/ωc)/(1+ i*ω/ωc)     with (i=sqt(-1))
and the phase shift: phi=atn(ωc/ω), so Phi is neat zero if ωc<<ω...
(if i don't make an error...)

2) The high limit is set by the core loss...
And the phase depend mainly of  ω/ωc.

@+

It is surprisingly tricky to make a really good current sensor that has a wide bandwidth and tight accuracy.  Tektronix has an excellent system that works from DC to past 100MHz, but costs about $6000. to get started.  Much narrower bandwidths are much easier.  Off the shelf $3. Hall Effect sensors manage 80kHz.  Many switching power supplies these days need to sense from DC to several MHz for pennies.  By far the most popular option is a current sense resistor of some form.  If one uses a low inductance configuration and/or compensates for the inductance that is intrinsic then one can get clean measurements without spending much money, all with certain caveats.  TinselKoala is running well below 1MHz.  There are a number of good options for him.

The sorts of problems that he is trying to solve and therefore the sorts of things that Ken Wyatt usually wants to measure are at frequencies well above what TinselKoala is interested in measuring.  TinselKoala will need a current sense transformer that has a cut-off frequency is well below those that Ken Wyatt would ordinarily use.  If TK could get one, a used Tektronix P6021 or P6022 would be nearly ideal.

[isim]

@TinselKoala
"The QEG people have shown the use of the Stangenes current transformer, I think this one:
http://electricalproducts.stangenes.com/item/current-transformers/wide-band-current-transformers/0-5-0-1w#Specifications
and I believe this to be a straight current-to-voltage type without any electronics inside."
- No electronics inside, yes, and very good spec, yes, but don't forget it's a a "current to current" transformer, you need to connect it directly to the BNC 50ohm input of your oscilloscope to get this spec, and do not use the 1Mohm probe!
                       0.1Volt/Amp is with nominal R(50ohm). As for all other CT!
"Accuracy : ±0.5% initial pulse response for all models. Specifications for transformer ratio, accuracy, and droop are at open circuit. Rise time and bandwidth are when terminated with 50 ohms. All models are electrostatically shielded and have a 50 ohm output impedance."

@+

[isim]

@MarE
"By far the most popular option is a current sense resistor of some form. If one uses a low inductance configuration..."
I agree totally with you. A 0.01 ohm purely resistive load even at 20A is perfect for these frequency.
And the signal it's large enough to make phase measurement...
And it cost nothing if made of thin wire of Cu, brass or even iron, if we keep R low enough. It's even possible to adjust R by scraping the little wire.
Just connect the ground probe between the R and the coil!
@+

[MarkE]

@MarE
"By far the most popular option is a current sense resistor of some form. If one uses a low inductance configuration..."
I agree totally with you. A 0.01 ohm purely resistive load even at 20A is perfect for these frequency.
And the signal it's large enough to make phase measurement...
And it cost nothing if made of thin wire of Cu, brass or even iron, if we keep R low enough. It's even possible to adjust R by scraping the little wire.
Just connect the ground probe between the R and the coil!
@+

There are also methods to use the coil itself as the sensor based on the coil resistance and inductance.  A lot of high current power supplies use that sort of method in order to avoid the power loss of a dedicated current sense resistor.  I have a colleague who is very good at implementing that method.  I'd rather avoid all the work and just use a dedicated current sense resistor of an appropriate value and power rating whenever I can.