Hameg Analog Oscilloscope

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Like I suspected, time domain.
Frequency shift absolutely resides in the time domain.

[Skippy]

Aghhh!
Nino.... you need damping on your pickup coil, man. All that sine crap doesn't really exist. Try adding something like 330 Ohms across your pickup coil, that may get you roughly right. Experiment with it until the Equinox 10kHz single-freq looks like a decent square-wave.

[EL NINO]

He also surprised me the shape of the wave ..., So I try to use resistor = 330ohm for the next measurement ..,thank you for the advice of Skippy...

[Skippy]

Nino: Read this thread from Post #93 on. It concerns damping resistor choice, and it's effects.
https://www.geotech1.com/forums/show...-Machine/page4

[EL NINO]

I still measured the inductance of my probing-receiving coil = 0.281 mH ..

[Skippy]

Based on your waveform ringing/resonating at about 420 kHz, and the inductance of the coil being 0.28 mH , I calculate you need a damping resistor of 370 Ohms. So pretty close to my original guesstimate. Try values from 330 Ohms up to 470 Ohms, and see what looks best when viewing a square-wave single-frequency Nox output.

[Carl-NC]

I made some Equinox 800 scans on my osciloscope...

Guys, this is just awful. If you're NOT getting waveforms like this:



then you are doing it WRONG. And when you post a bunch of wrong information on other web sites, it creates a mess.

[EL NINO]

Greetings to you, Mr Carl .., I agree with you from the wrong measurement of the possibility of others misleading ...


On the new measurement I used the Measuring Coil and 10.43 kOhm resistance, the results are better: I get a square wave ..:



When measuring with Average, I get the following results:




At very low average:

[Skippy]

Arghhh! Arghhhh! [bashes head against PC screen yet again Smiley]
1 ) When Carl says "If you're NOT getting waveforms like this: "EqBeachPark.png" .. then you're doing it WRONG"
he's misleading you. You are using a coil of wire ( on a ferrite rod ) as a pickup coil, so the waveform you see will be a square wave like this:
https://www.geotech1.com/forums/atta...8&d=1526134483

2 ) Stop using scope averaging, it's not needed, and is only useful when the signal repeats, and you trigger at the correct point in that repetition. Otherwise, you just get crap.

3 ) It looks like you need a lower value damping resistor on your pickup coil.

[EL NINO]

Yes, I get something similar, even when it's not perfect :



I'm trying to use a suitable resistor ... and use your advice 1-2-3.... to improve the measurements ..,, ..

[green]

Yes, I get something similar, even when it's not perfect :

[ATTACH]45597[/ATTACH]

I'm trying to use a suitable resistor ... and use your advice 1-2-3.... to improve the measurements ..,, ..

I would be interested in what you get for a scope trace, 50us/div(Carl's trace)with Rd around 300 ohms(Skippy's suggestion)and another with a lower resistance maybe closer to 10 ohms.

[WM6]

Due to (to high) inductive coupling between detector coil and sensor coil, which, no matter of ideal Rd,
always import some sort of deformation to measured signal, it is better to take border sensing distance
between detector coil and sensor coil.

[EL NINO]

Thanks WM6...,I will try all the recommendations, I assume that the resistance is connected in series ....

[Skippy]

No! It's from one coil wire to the other.

[EL NINO]

so the parallel connection of the resistor OK, thank you for your time Skippy..