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From: George Herold on 12 Jul 2010 12:31
On Jul 12, 12:13 pm, john1987 <conphil...(a)hotmail.com> wrote:
> hi,
>
> Frequency is 300KHz. 200 peak to peak times 2A. Signal source is HIP
> 4081 driving four MOSFETS. The other end is not grounded. Accuracy
> requirent not known yet.
>
> John

Is the inductor the load? Or is there somthing inside the inductor
that is getting hot? IOW, Does the load look inductive or is it
resistive.

You might want to rectify the siganl first and then use a resistor
divider to reduce the voltage. (Less error from the diodes that
way.) Though I don't know if big fat diodes are fast enough.

Apex makes some high voltage and high current opamps, but they are not
cheap! say ~$50 or more each.

George H.

From: john1987 on 12 Jul 2010 12:49


Hi,

The load is another coil with different number of turns plus a diode
rectifier and a resistive load. The resistive load values can change
that will also change the amount of current and voltage on the primary
side and that is why I need to monitor the primary coil voltage and
keep it constant. So, primary coil --------------> air
------------------> secondary coil --------------------> load. Need
advice on the feedback monitoring system

Thanks
John
From: Joerg on 12 Jul 2010 14:12
john1987 wrote:
>
> Hi,
>
> The load is another coil with different number of turns plus a diode
> rectifier and a resistive load. The resistive load values can change
> that will also change the amount of current and voltage on the primary
> side and that is why I need to monitor the primary coil voltage and
> keep it constant. So, primary coil --------------> air
> ------------------> secondary coil --------------------> load. Need
> advice on the feedback monitoring system
>

Would a simple peak detector work? Transformer 20:1 or something that
can be had off the shelf -> rectifier with properly set attack and decay
times -> to uC or whatever needs this data.

--
Regards, Joerg

http://www.analogconsultants.com/

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From: john1987 on 12 Jul 2010 14:33
Hi,

Thanks for the reply but I did not understand the following part of
your reply

"rectifier with properly set attack and decay "
"times -> to uC or whatever needs this data."

Would you please explain a little more.


John

From: Joerg on 12 Jul 2010 16:16
john1987 wrote:
> Hi,
>
> Thanks for the reply but I did not understand the following part of
> your reply
>
> "rectifier with properly set attack and decay "
> "times -> to uC or whatever needs this data."
>
> Would you please explain a little more.
>

Assuming you want to measure a peak amplitude, place a rectifier, same
as you would in a linear power supply. Make the capacitor large enough
to tide you over the cycles but not a lot more. Then you end up with a
DC voltage (with some ripple on there) that is proportional to the
amplitude of your 200V spike, largely independent of the shape of that
spike.

There are many other options such as sample & hold but for that we'd
need to see your schematic.

--
Regards, Joerg

http://www.analogconsultants.com/

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