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Old 11th November 2010, 12:56 PM   #11
AndrewT is offline AndrewT  Scotland
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Hi Eva,
can you update the dead links?
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Old 11th November 2010, 06:14 PM   #12
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I use this circuit:
Inductors
for power inductors.

For small signal parameters (L, R), I set up a parallel resonant tank with the function generator. Ohm's law does the rest.

Tim
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Old 16th November 2010, 12:49 PM   #13
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Quote:
Originally Posted by veze View Post
any one still have the scheme
Hi Veze,

thanks for your PM I will respond to it here.
Check out the link Sch3mat1c gave, my circuit is actually very similar, except that I have added the generator on the board but you could instead use a function generator as well controlling the switching FET.

Notice that this circuit is fed with a negative voltage from ground, so if you use a PSU with only positive voltage feed and where the ground is connected to the mains ground make sure you know what you do because the oscilloscope ground is directly connected to mains ground and you can destroy your equipment if improperly connected, or use a full transformer to isolate the oscilloscope from mains ground.

If any more questions just post here and I will check back, good luck!

Michael
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Old 4th May 2013, 04:17 PM   #14
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I'm going to resurrect this thread i need some help.


Do anyone here still have the PCB files for this file or an equivalent version ?

Thanks in advance.!
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Old 8th May 2013, 10:50 AM   #15
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bump
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Old 9th May 2013, 01:14 AM   #16
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Its easy to get fooled by cheap LC meters.

I designed a SMPS and had to have a certain leakage inductance.
My multi-meter said the inductor was 120uH and my USB LC meter said it was 60uH.
When I measured it using a resonant circuit, sig gen and scope it was in fact only 10uH which is why my SMPS over current kept tripping out.
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Old 9th May 2013, 02:46 AM   #17
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Quote:
Originally Posted by nigelwright7557 View Post
Its easy to get fooled by cheap LC meters.

I designed a SMPS and had to have a certain leakage inductance.
My multi-meter said the inductor was 120uH and my USB LC meter said it was 60uH.
When I measured it using a resonant circuit, sig gen and scope it was in fact only 10uH which is why my SMPS over current kept tripping out.
Very true, what brand of meter was that ?

I do however understand a inductor meter cant provide parameters like Saturation currents ect.. that why i need the schematic or PCB that eva posted. or something similar.

i could try and build one.. what i need a PWM signal adjustable ,frequency adjust, some compensation network, what rating transformer ? a simple mosfet..
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Old 9th May 2013, 02:56 PM   #18
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Quote:
Originally Posted by Reactance View Post
Very true, what brand of meter was that ?

I do however understand a inductor meter cant provide parameters like Saturation currents ect.. that why i need the schematic or PCB that eva posted. or something similar.

i could try and build one.. what i need a PWM signal adjustable ,frequency adjust, some compensation network, what rating transformer ? a simple mosfet..
It was a £25 Farnell LCR meter.
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Old 9th May 2013, 10:59 PM   #19
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Quote:
Originally Posted by Reactance View Post
Very true, what brand of meter was that ?

I do however understand a inductor meter cant provide parameters like Saturation currents ect.. that why i need the schematic or PCB that eva posted. or something similar.

i could try and build one.. what i need a PWM signal adjustable ,frequency adjust, some compensation network, what rating transformer ? a simple mosfet..
You can make an accurate L meter with a scope and signal generator.

You need a resistor, capacitor and the inductor under test.
Wire them all in series.
Shift the sig gen up and and down until you get least ac across LC and this is the resonant frequency.
Then L = 1 / ( 4 PI PI F F C)
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Old 10th May 2013, 07:05 PM   #20
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Quote:
Originally Posted by nigelwright7557 View Post
You can make an accurate L meter with a scope and signal generator.

You need a resistor, capacitor and the inductor under test.
Wire them all in series.
Shift the sig gen up and and down until you get least ac across LC and this is the resonant frequency.
Then L = 1 / ( 4 PI PI F F C)
Thanks for the tip i actually have a meter already ive referenced the reading to a off the self inductor and its about -/+ 10% accuracy.

But i need the circuit at the start of this thread see with this circuit i can go beyond just reading inductance i get get useful parameter like current, core saturation, frequency ect..

i think it should be simple enough looking at the SG apps notes there is a sample circuit i can just use to create a frequency sweep (limited to 300kz single ended, 150kz + 150khz push pull per phase) the problem im having is the other components around it like compensation, reset resistor, supply voltage.. uhmm
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