Originally posted by Qiaozhi
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Vallon VMH3CS Mine Detector
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Originally posted by Altra View PostIf your scope has trigger "Holdoff" control you can adjust this to ignore all trigger sources during a time period. On my Tektronix digital scope, it can be set by uS or mS increments. In this case you would set it to just past the opposite polarity tx, or about 600us
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Again; an inductive coupling is the way to go.
I would make same diameter, same inductance and same resistance copy coil and hook it on scope.
Than place in same plane as original coil and perform measurements.
Most probably it will need copy coil to move relatively to original slightly offset, but it is easy observable on scope display.
That's for measurements when you don't want to mix up into original circuit nor affect origin signal.
...
Ferric.. 77 is just number, meaning nothing.
Keep up the good spirit and you'll easily see many more numbers.
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Originally posted by Ferric Toes View PostI take it easy now and don't look for work where I am under any pressure. When you reach 77, the years go by much quicker and sometimes I will go under the radar for a while doing different things and then something fires up the interest in hobby detectors with slightly different technology and I'll be back, like now.
Eric.
For all that your work offer to people like me over the years.
Thanks again
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Originally posted by Qiaozhi View PostThe Tektronix 2445A does have a trigger hold-off function, so that's a possible solution.
There is no indication so far that it is anything but pure PI. If I hold a chunk of steel close to the coil, I can even see the normal decay. Now to build a diode clipping network to get rid of the flyback transients and see what is going on at lower levels.
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Eric,
I want to thank you for sharing your technical knowledge on various forums over the years. It was your forum that taught me about PI detectors and motivated me to write my "Making a Fast PI Mono Coil" article with the encouragement of Carl who runs this forum. It is good to see you exploring different PI designs again.
Thanks
Joseph J. Rogowski
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Originally posted by Ferric Toes View PostHere are a couple of shots of the coil current on the Vallon detector with 0.1 ohm series resistor.
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Originally posted by Davor View PostIt appears there are both acceleration and deceleration mechanism involved. There are steep, but near-linear current slopes on both sides. Interesting.
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Originally posted by bbsailor View PostEric,
I want to thank you for sharing your technical knowledge on various forums over the years. It was your forum that taught me about PI detectors and motivated me to write my "Making a Fast PI Mono Coil" article with the encouragement of Carl who runs this forum. It is good to see you exploring different PI designs again.
Thanks
Joseph J. Rogowski
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Originally posted by Ferric Toes View PostHi Davor, I wonder if they are using the high voltage spike from one pulse to kick start the next opposite polarity pulse in order to get the fast rise time. A diode capacitor snubber would store the 250V which would be in the correct polarity to do this.
I wonder if there is a difference in timing when ground balance is on. I'd expect to see some if Paltaglou principle is involved.
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Originally posted by Ferric Toes View PostHi Davor, I wonder if they are using the high voltage spike from one pulse to kick start the next opposite polarity pulse in order to get the fast rise time. A diode capacitor snubber would store the 250V which would be in the correct polarity to do this.
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