new MineLab Machine

[Chiv]

S0 used coil I made for barra and stuck the scope on. dose not mean to much for me but I know I'm pulling stuff up that beach hunter have missed over the years. did have a play in the red dirt country but only lead projectiles and brass shells found.
any way did my best to get the screen shots as clean as I could, only real know hows to use the scope to set the coils up on the barra

5khz
10khz
15khz
20khz
40khz
multi

[Skippy]

I'm puzzled. The timebase 'knob' seems to indicate 100 millisec per division. There's another readout below the trace saying 50 millisec/div. Either way, they are miles out ... surely to see a 5kHz square wave, you would be wanting timebase = 100 microsecs/div, so one complete cycle covers 2 divisions? And multi would need about 25 microsecs/div. so that one full cycle covered most of the 'screen'.

[waltr]

I'm puzzled. The timebase 'knob' seems to indicate 100 millisec per division. There's another readout below the trace saying 50 millisec/div. Either way, they are miles out ... surely to see a 5kHz square wave, you would be wanting timebase = 100 microsecs/div, so one complete cycle covers 2 divisions? And multi would need about 25 microsecs/div. so that one full cycle covered most of the 'screen'.

Yes, also Freq displayed is 50Hz so scope sampling is ALIASING the signal to 50Hz.
Scope timing base needs to be much faster.

[Skippy]

The internet tells me that Australia has 50 Hz mains, like here in the U.K, so I'm tempted to say that the repeated 49.8 Hz is largely mains pickup, with a bit of aliasing thrown in.

[nakky]

https://www.youtube.com/watch?time_c...&v=LOLQGSuMPjo

Nakky

[dbanner]

https://www.youtube.com/watch?time_c...&v=LOLQGSuMPjo

Nakky

I watched the video. Wow, things have come a long way, haven't they. That circuit board is amazing, so tiny. Hard to believe a few grammes of weight could be so pricey. No wonder tech companies make so much money.

[waltr]

It is not the hardware that is pricey---it is the Engineering time to create the hardware and Firmware that is pricey.

[Carl-NC]

I used to design chips for Analog Devices. I would tell people, "The first opamp costs $1 million; after that, they are 10¢ each."

[daverave]

I watched the video. Wow, things have come a long way, haven't they. That circuit board is amazing, so tiny. Hard to believe a few grammes of weight could be so pricey. No wonder tech companies make so much money.

the video looks interesting and i guess the russians will learn a few tricks from it....personally i would prefer a white's v3i any day.

[Chiv]

ok had another crack at this scope set up. don't think scope quick enough for multi frequency, as it jumps all over the screen no mater what time bass you set it on

[waltr]

You successfully captured it this time, triggering on this type of waveform is difficult.
The scope is showing a Pulsed - resonate waveform with alternating Positive-Negative pulses.

Images are a bit too small to measure the resonate frequency but each capture does show the Pulse rate differences.
Of course the Real Magic of how the detector works is in what is done to analysis the signals.

This is similar to Teemo's Pulse Oscillation detector.
http://www.geotech1.com/forums/showt...tector-project
http://www.digiwood.ee/8-electronic-...tector-circuit

Check his scope shot in the detector description.

[Taktyk]

ok had another crack at this scope set up. don't think scope quick enough for multi frequency, as it jumps all over the screen no mater what time bass you set it on

[ATTACH]42970[/ATTACH]

[ATTACH]42971[/ATTACH]
[ATTACH]42972[/ATTACH]
[ATTACH]42972[/ATTACH]
[ATTACH]42973[/ATTACH]
[ATTACH]42974[/ATTACH]

Your measurement is bad. Check the normal oscilloscope with probe x10.

Regards

[kt315]

agree with taktyk. you see self resonance on your o-scope probe+input.

[green]

Does the pickup coil need a damping resistor?

[Chiv]

ok here is X10 pic on multi

I shall try damping resister tomorrow ,but x10prob just can not get it to stay on screen , maybe it the scope it self, thanks for the input