On 04/12/2014 03:23 PM, d...@irtelemetrics.com wrote:
Magnus,
You are very much on the track that I was thinking. I belive you are
absolutly correct in that a 90 degree phase shift would be ideal.
Coming into the conversation kinda late.
Sounds like you're building an induction heater
Some terminology to consider. There is the natural and damped frequency
to consider. That is, as you load the circuit, the resonance changes. If
you drive it with infinite impedance, you are at the natural frequency.
Loading it will shift the frequency, hence the damped frequency.
I would try to
On 11/04/14 22:15, Dan Kemppainen wrote:
Hi all,
I'm thinking about an upcoming project, if this is off topic please
disregard or contact me off list. :)
I have a large LC tank, with a very lossy inductor. Being driven by a
pulse width push pull driver, that is digitally controlled. The driver
Keep in mind that anything you connect across your tank circuit will affect its
resonant frequency and Q (signal source and measuring device). You need to make
sure your equipment is very loosely coupled to the UUT through small value
capacitors for instance.
Didier KO4BB
On April 11, 2014
Magnus,
You are very much on the track that I was thinking. I belive you are
absolutly correct
in that a 90 degree phase shift would be ideal.
I did a bit more digging last night, and it turns out that an XOR phase
comparator
looking at the tank voltage and drive voltage may be ideal, as
It is very easy to make an impedance phase detector by
inserting a toroidal current transformer in series with
the load under test. The center of the secondary is
connected to the load through a capacitor. Each end of
the secondary goes to a diode detector. When the
load is resistive, the DC
On 12/04/14 21:23, d...@irtelemetrics.com wrote:
Magnus,
You are very much on the track that I was thinking. I belive you are
absolutly correct
in that a 90 degree phase shift would be ideal.
I did a bit more digging last night, and it turns out that an XOR phase
comparator
looking at the
Hi all,
I'm thinking about an upcoming project, if this is off topic please
disregard or contact me off list. :)
I have a large LC tank, with a very lossy inductor. Being driven by a
pulse width push pull driver, that is digitally controlled. The driver
circuit will couple through a N:1
At resonance, an LC looks pure resistive.
For a parallel LC, sample the voltage across the LC and the drive current,
and tweek the frequency until they are in-phase.
For a series LC, sample the voltage across the L or C and tweek as above.
If you want to do it analog, dither the frequency a
First order approximation of course would be to sweep the frequency and
look for a dip (peak for series resonant) in the DC current drawn by the
driver.
On Fri, Apr 11, 2014 at 4:15 PM, Dan Kemppainen d...@irtelemetrics.comwrote:
when actively driving a tank circuit, how do you
know you are
I have a large LC tank, with a very lossy inductor. ...
So the question is, when actively driving a tank circuit, how do you know
you are driving it with the same frequency ad the same phase it naturally
oscillates at.
If it's lossy, the peak will be broad so tuning the driving frequency
I would have done exactly what Hal said. I do this all the time when trying
to figure out the LC tanks operating frequency. An example keeping this
time nuts friendly, the d-psk-r circuits at 60 Khz. I am lucky in that I
can add or subtract C on the stuff I work on.
Regards
Paul
WB8TSL
On Fri,
That's why you want to look for the phase of the tank impedance. The phase
goes through zero at resonance. It is far more precise. The steepness of
the phase v. frequency plot is steep w/ a high Q circuit... flatter w/ a
low Q tank. Either way, it does go through zero at resonance.
The phase v.
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