Ebinger damping process detectors

[Teleno]

TI am curious to see what other advantage this method may have if any.

The same advantage as PI, a simpler coil, but the ability to discriminate is not compromised.

The oscillator should be placed in the coil head to avoid fluctuations caused by a length of cable.

[Davor]

OK, patent DE4212363 has nothing to do with PI.

[Teleno]

A deadband circuit is very good at detecting tiny changes in the oscillator's amplitude. So much that no amplifier is needed. I'm using an MCU directly connected to the deadband's output to do oversampling/decimation and integration. Sampling is in synch with the oscillator's frequency to avoid filtering. It works! The higher the oscillator's peak voltage the better. I'm doing 40V for a DC current consumption of 170mA.

[samu]

Hello everyone,
Any advance on this matter?

It's seems like a nice detector to build easily at home. The fact that even without amplifier is capable of detecting metals with a simple coil is a really promising start.

I have read everything is posted and still not sure about what exactly "damping" means. If I'm right, the point is to measure the oscillating attenuating signal that is created after the coil is driven with a pulse, it's that OK?

Thanks in advance

[kt315]

i see you want to be theoretik. so nice book to read first for you
https://www.amazon.com/Inside-Metal-...DDMSEQ5SG7TWCJ

[samu]

Thank you for the advice, however, I had already read the book. Anyway, there's nothing related to damping metal detectors in the book, just a brief statement in page 145:

"While it might be possible that this decayed ringing is useful for detecting metal, it is not used in traditional pulse induction designs"

What I wanted to know, is if this "damping method" relates to that, to the measure of the "decayed ringing" of an undamped PI. I suppose it's that, but not sure, could be something else I don't know.

Thank you in advance

[Qiaozhi]

Thank you for the advice, however, I had already read the book. Anyway, there's nothing related to damping metal detectors in the book, just a brief statement in page 145:

"While it might be possible that this decayed ringing is useful for detecting metal, it is not used in traditional pulse induction designs"

What I wanted to know, is if this "damping method" relates to that, to the measure of the "decayed ringing" of an undamped PI. I suppose it's that, but not sure, could be something else I don't know.

Thank you in advance

If you're referring to this statement by Teleno -> "A free-running oscillator whose search coil is built as an LC circuit, experiences a damping effect by proximity to metal. A change in amplitude occurs that's translated into an acoustic signal after electronic processing."
then this is the same method used by the Off-resonance Probe in Chapter 4 of ITMD.

In this case, the reference to "damping" is not the same as that used for PI designs. In a PI you need to critically damp the received signal in order to achieve the fastest settling time, whereas "damping" in this case refers to the amplitude of the TX signal being reduced in the presence of a metal target.

[samu]

Thanks a lot Qiaozhi,

I'd never thought that it was just that. It's impressive what Teleno achieves without amplifier with this method. I built an Off-resonance circuit years ago, but the sensibility was far from that, so I was sure it had to be something different. Maybe the oscillator Teleno used is much better than mine, or the dead-band circuit is so good, I'll try one of this days.