Verator front end

[Davor]

There is a flat top for a good reason - Q factor of this series resonance circuit is very low. A kind of low Q that you prefer. The whole point of series connection was to compensate inductive reactance and get into 0° vicinity. This is because current is not allowed to recirculate between L and C like parallel tank does, so there is really no peak as you drawn it.

You may test it for yourself

[Qiaozhi]

Myths certainly do not needHere's your emulator shows the phase and frequency response. But in fact, it does not correspond to what we have. Not shown is a resonance at 25 kHz for example. He is strong enough to influence.

When you run a SPICE simulation in the frequency domain, you must be aware that this is restricted to small-signal analysis. In other words, the simulation models are linearized around the operating point. So it is no wonder that the results can sometimes be different to reality. A large-signal time domain analysis, followed by an FFT, would produce the correct results.

[Verator]

No guys ... Everything is much easier. No there is no "Q" factor. Take a real coil, a soldering iron, how to connect the generator and oscilloscope. Will see.
At the coil has a private capacity!!! She gives a resonans.

[Davor]

True, but self resonance is usually above the working frequency, and lumped idealised element models are fairly close to reality.
The most problematic idea circulating in metal detectoring world is that a parallel tank is a band pass filter, while in fact it is not. It is a second order low pass filter, as the voltage source (EMF) is in series with a coil. Because such filter has steep phase transition it is problematic on many accounts. But not when Rx coil is configured in series resonance. It is much nicer because there is very little current flowing through Rx coil. It is terminated by high impedance, hence there is a low Q, and very very little frequency dependence. And it does not ring.

[Verator]

Yes, it's true. I agree 100% Parallel circuit I use a LPF filter because the high harmonic content of the signal transmitter. When using a serial loop then a lot of debris. This solution is more suitable for sinus transmitter. But due to the large dynamic range Verator withstand any inclusion. There was no difference in the work I have not seen. To make the initial contour line Garrett uses the input RC filter load

[Verator]

Today specifically measured the parallel resonance circuit for the frequency of 9.6 kHz. Circuit tuned to 5.6 kHz is phase shift therein 85g. What can there be a non-linearity of the phase? While he does not have a resonant circuit for the operating frequency and serves as a good LPF. No problem guys.

[Davor]

It is not non-linearity, but slope. I think I understand your point. As neither of these solutions is performing much better than the other, your point is just fine.

Of many nice features that Verator has, I like the "faze" adjust a lot. It enables much easier replacing coils, as only this one adjustment is enough.

[Verator]

Linearity phase sensor is necessary to subtract the soil to vectors were correct. Error in the metal does not make any difference.

[Davor]

Very true, but it is not so strongly dependent upon the working frequency. Hence only the tank resonance, or no tank resonance, will make big difference. Low noise input circuitry can be made as series tank connection that has low Q and very flat phase transition, and that is the solution I'm suggesting for a future Verator build.

It is not that there is anything wrong with it. There are only some other means to get there and have even better rig.

[Verator]

But it will not Verator, it will be a different device. Elector!

[Davor]

If you look closely, Elektor detector did not use all the potential of the tank locked loop approach. The phase supplied to 4046 is shifted, and there is a second PLL chasing the first one, just to establish a phase shift for discrimination. A single 4046 could do the job much better.

[Verator]

I would like to ask whether it is possible to receive in the mail a model for LTspice PLL4046. аsy

[Davor]

Here you are, a new development. I moved some parts here and there so that signal path gets compensated delay - the invertor is now inverting the comp_in signal instead of the coil drive. This way any delay incurred by transistors switching is mutually compensated.

You'll find in a zip file both .asc and .asy of a 4046, and a working schematic that utilizes them. This is a hierarchical model, so instead of a library, a 4046 is designed as a sub-schematic. It works pretty close to reality.

Enjoy

[Verator]

Thank you. We will investigate.

[Verator]

slightly improved. Transistor BS250 (!)