Deus II: About the oscillogram

[Carl-NC]

Oscopes have a terrible time at triggering on a MF waveform and the frequency shown is its trigger frequency, which may have little to do with the actual frequency. This is why, at 1:02, he freezes the waveform. You can also use the "holdoff" function to set up a proper trigger. With the waveform frozen, you then look at the time divisions and count out the main frequency, which is where the overall waveform starts repeating:



In this case, the time/div is 20us and the estimated period is 125-130us, or 7.7-8.0 kHz. You count the number of polarity transitions (5) and you know the high frequency is 5x the low, or 38.5-40.0 kHz. I already knew that the nominal frequencies for the D2 are 7.8 & 39 kHz.

[Mark-VA]

Thanks for the excellent explanation. Now I'm starting to understand. The D2 only transmits at 2 frequencies (max), never what I consider multi (3) and other times only 1.

I would love to have a scope of that magnitude and check every possible frequency combinations the Deus claims to have. Three choices of each program, excluding the Deus mono.

Just to know.

[JoyJo]

Oscopes have a terrible time at triggering on a MF waveform and the frequency shown is its trigger frequency, which may have little to do with the actual frequency. This is why, at 1:02, he freezes the waveform. You can also use the "holdoff" function to set up a proper trigger. With the waveform frozen, you then look at the time divisions and count out the main frequency, which is where the overall waveform starts repeating:



In this case, the time/div is 20us and the estimated period is 125-130us, or 7.7-8.0 kHz. You count the number of polarity transitions (5) and you know the high frequency is 5x the low, or 38.5-40.0 kHz. I already knew that the nominal frequencies for the D2 are 7.8 & 39 kHz.

And how does it work if the low-frequency current is 10 times (for example) greater than the high-frequency current with such a signal as in the photo? I'm conducting similar experiments and I can't get a result.

[Carl-NC]

If the waveform is done right, then an FFT of the voltage waveform (as shown) should show f1 and f5 with about the same amplitude. Since f5 is 5*f1, then f1 should have 5 times the current amplitude as f5. But at the receiver coil, the induced voltages are again equal because of the derivative function.

[JoyJo]

I didn't understand a little, I'm sorry.

[Carl-NC]

Suppose you have a 1mH coil driven with a 10vp-p sine wave. If the frequency is 5kHz then the coil impedance is 31.4Ω and the current is 318mAp-p.
Now suppose you drive the coil at 25kHz. The coil impedance is now 157Ω and the current is 63.7mA. So for the same voltage drive level, 5kHz will produce a 5X stronger B-field than 25kHz.
However, when you get back to the RX coil, the induced voltage is a function of dB/dt, where B is a function of sin(wt). Therefore, the induced RX voltage will be equal for the two frequencies even though the low frequency produces a stronger TX signal.
Same thing happens in a multifrequency system when the multi-period waveform is designed to equalize the effective TX voltages. The low frequency current will be higher, but the RX results should be about the same.

[JoyJo]

At a low frequency (5kHz), the current in the TX coil will have a much larger value than at a high frequency (25kHz). What about this? Or when using a multi-frequency, there will be no significant difference in currents?

[Riss]

Digital processing of information from 3 frequencies is not a problem - software or for modern processors. But repeatability of parameters when processing 3 frequencies causes a lot of headaches in serial production (probe setup of SPECTRA V3 ). The accuracy of discrimination and the degree of clipping of the soil effect when processing 3 frequencies increases only by about 20-30%, but this improvement is hardly felt in the unpredictable nature of the terrain - soil conditions. the current through the coil of DEUS2 is linear - the 3rd, 5th, and with sufficient amplitude the 7th and 9th harmonics of the fundamental frequency are emitted. The "inset" in the DFX oscillogram (which is exactly the same in DEUS2 - #121 , - the narrow pulse between digits 1 and 2 and below digit 4 ) can be easily understood if we take a sheet of graph paper and draw the phases of the sinusoids of the higher harmonics - third and fifth. 90 angular degrees at the third harmonic are equal to 30 angular degrees at the first harmonic, accordingly 90 degrees at the fifth harmonic are equal to 18 angular degrees at the first harmonic. The even harmonics do not introduce an error in the phase detection of the first harmonic, since their energy is zeroed in every 180 degree fragment (they are completely absent in the linearly increasing/decreasing current through the coil). odd harmonics, however, have 1.5 half-periods (360 + 90 degrees) - for the third harmonic; 2.5 half-periods (2x 360 + 90 degrees) - for the fifth harmonic. The DFX oscillogram, which works on the first (3) and fifth (15 kHz) harmonics, is the cheapest possible and optimal solution for a two-frequency detector - enough uniform sensitivity for all targets, greatly improved 5th harmonic emission over meander 180 degrees up/180 degrees down ( FISHER CZ5 –CZ 6) and at the same time simplified analog 5th harmonic filtering in channel 3 kHz - the insert "eats" this problem ... in summary - all detectors with linearly increasing current through the coil emit a theoretically infinite number of higher harmonics , but usually only handle 2 frequencies simultaneously. the luck of the searcher is much more important than the technology of the detector he works with...
https://ocw.mit.edu/courses/18-103-f...sis-fall-2013/
https://mathworld.wolfram.com/FourierSeries.html

[Mark-VA]

Wow, what an answer.

[Skippy]

Mark asked in a PM if I had any more info on the D2 transmissions etc.
In addition to what I posted earlier in this thread ( post 38 etc ), I also posted on the DetectorProspector forum, as the question about D2 freqs was raised.
Maybe there's some additional info in it that may explain ( or confuse ) things.

Link:
Not Much Chat About Multi Frequencies - XP Deus II Forum - DetectorProspector.com

[Mark-VA]

,,And there is nothing new under the sun???with one exception - 7 minute ? 8min. 20 sec ...

https://www.youtube.com/watch?v=E2AYJp2uH2U
we all owe a "thank you" to this Russian with the oscilloscope

Did a Russian to English translation (available on YouTube) and the guy states the wave form frequencies are the same for programs 1 through 4. No difference. He also mentioned the oscillogram of the Equinox and the Deus 2 are very similar.
Time stamp 1.10 and 3.16.

He also mentioned the possibility of doing a more detailed video of the programs at a later time.
Anyway, reading all the translations give a good understanding of what he is saying.

[JoyJo]

You surprise me. Bloggers can only evaluate worms of TX oscilloscopes. But there is also, remember, a reception area. more precisely, digital processing. With the same TX signal format, it can be digitally processed in different ways. So it turns out that for programs with the same TX wave, there is different processing in the microprocessor. It is enough to change the parameters of digital filters, averaging or amplification and you will get a completely different result.

[Skippy]

Quote:" ... the guy states the wave form frequencies are the same for programs 1 through 4"
Well at least that agrees with what's already been observed:


"The modes:
P1 : General
P2 : Sensitive
P3 : Sens FT
P4 : Fast
P8 : GoldField
P12 : Beach; all run at 8.08 kHz & 40.4 kHz, a 1:5 ratio.
-----
P5 : Park
P9 : Relic
P11 : Beach; all run 8.08 kHz & 24.24 kHz, a 1:3 ratio.
-----
P6 : Deep HC
P10 : Dive; both run 4.76 kHz & 14.3 Khz, a 1:3 ratio ( not unlike the Fisher CZ range, but a different waveform shape )
-----
P7 : Mono, does what you'd expect, a single freq square-wave, just like the Equinox."

Quote:"He also mentioned the oscillogram of the Equinox and the Deus 2 are very similar."
Very similar, apart from being totally different.

[Carl-NC]

Quote:"He also mentioned the oscillogram of the Equinox and the Deus 2 are very similar."
Very similar, apart from being totally different.

The D2 runs at 7.8kHz and 39kHz. The Equinox runs at the same frequencies but adds in 2.6kHz. It makes the waveforms look quite different, but they are not as different as it looks.

[Skippy]

"The Equinox runs at the same frequencies but adds in 2.6kHz" It adds in 18.2 kHz. And the fact that the D2 never uses more than two frequencies, and the Eqx never uses less than 3 frequencies is sufficient for me to justify stating they are completely different.