Hi,
I am interested in this. I am working on a similar design.
It has good FE discrimination.
There is frequency shift due to a metal target.
I believe this is no different to the frequency shift in a PI pulse, or the frequency (not phase) shift in a 'Induction Balance' detector.
All these technologies do the same thing to a target: Present a changing magnetic field.
The good thing about a free-running oscillator like this is that the tiny shift in each cycle adds-up (compounds) over time, so if you measure over say 1000 pulses, you get a decent measurable change.
Another excellent thing is that power is not wasted in a resistor, it is re-used (i.e resonating)
I believe this style of detector can be more sensitive than any other technology.
I think:
To decrease the sensitivity to high resistance targets (wet sand and ferrite) : decrease the frequency.
I am interested in this. I am working on a similar design.
It has good FE discrimination.
There is frequency shift due to a metal target.
I believe this is no different to the frequency shift in a PI pulse, or the frequency (not phase) shift in a 'Induction Balance' detector.
All these technologies do the same thing to a target: Present a changing magnetic field.
The good thing about a free-running oscillator like this is that the tiny shift in each cycle adds-up (compounds) over time, so if you measure over say 1000 pulses, you get a decent measurable change.
Another excellent thing is that power is not wasted in a resistor, it is re-used (i.e resonating)
I believe this style of detector can be more sensitive than any other technology.
I think:
To decrease the sensitivity to high resistance targets (wet sand and ferrite) : decrease the frequency.
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