Stability of the VDI scale

[JoyJo]

The TX phase should not shift. Phase shift TX is a negative effect of temperature and soil on the inductance of the TX coil.

[pito]

The current through resistor is the same as in Tx coil so phase of voltage on it is related to phase Tx current.

[JoyJo]

This is understandable... I thought something else was meant.

[JoyJo]

But what you have highlighted is the current sensor that consumes the cascade TX. The current consumption of the cascade is not equal to the current that flows in the TX coil.

[Artyom]

But what you have highlighted is the current sensor that consumes the cascade TX. The current consumption of the cascade is not equal to the current that flows in the TX coil.

[JoyJo]

What are your complaints?

[Smirnov-Arta]

...

Are you sure that the problem is only in the Tx circuit?
Heat or cool the Tx circuit together with the capacitor from 0 to plus 35 ( in tabular form 0, +5, +10,+15 +20, +25)...and look at what will change (resistance, inductance, amplitude, etc.) if it changes. If the inductance of the Tx coil were changing, then you would have the circuit frequency "changing/floating", but it's not, right? Then what does the contour of the Tx have to do with it? Maybe it's something else? Generally...one of the ways...for thermo stabilization of the coil and capacitor...they use/select capacitors with different TKE, but(!) this is if it is required...

[JoyJo]

No. It's not just the cascade that's the problem. The question was fundamentally different: why does the VDI scale not shift in branded metal detectors during the entire period of operation. Or in another way: How do branded metal detectors work without ferrite tuning?

[Carl-NC]

All detectors I've seen use either ferrite or a coin to set the initial reference point. After that, it's a matter of designing the TX, preamp, and demod clocks (or ADC sampling points) for low temperature drift.

[Smirnov-Arta]

...?

The answer is obvious. 1.Schematics/manufacturing/components are identical in each block. 2.Coil parameters are also L/Q. Thus the value of ferrite...the setting of the starting point/phase is almost the same and or has a slight discrepancy with the margin. When you buy a particular coil for Minelab, you don't adapt it to ferrite, right? Why? Because the block diagram/software has already been adapted according to ferrite for all coils suitable for this md. In simple words, unification. And consider it with a margin (!). This is in MD familiar to you, you can move the ferrite scale manually, adjusting to the ground a little...is that right?) Unify the MD and coil parameters and that's it... Well, almost everything).

[JoyJo]

Then how or by an algorithm can software compensation for the drift of the start point of the VDI scale be provided? no matter what parts and coils are used, there will still be phase drift.

[Smirnov-Arta]

...

> no matter what parts and coils are used, there will still be phase drift.
Sorry, I disagree. Based on the practice of making coils. But you can check for yourself. Take 1 block and make it...wind, etc. 2 coils with the same parameters in total(!). And put up a "ferrite". And you will see that the discrepancies will be at least 1-4 points/degrees. At the same time, keep in mind that you do it manually. And in factories, as you know, the winding of the same coils...automated/standardized, etc.

>Then how or by an algorithm can software compensation for the drift of the start point of the VDI scale >be provided?
"Ferrite is not a soil," do you remember such a phrase, etc.? This is on the one hand. On the other hand, make good sensor balance compensation.

[pito]

All either ferrite or a coin to set the initial reference point. .

either ground

[pito]

there will still be phase drift.

That's why we have dynamic mode = not affected by drift and static mode used for short time .........

[JoyJo]

What kind of dynamic mode are you talking about? Or about a metal detector with a dynamic mode of operation?