whats the basic equipt for PI building ?

[johnno]

Sorry to bore all you fine techs out there..but I would really like to build one of the PI detectors . I am NOT going to ask "which one is best".
I am asking what BASIC equipment do I require.
I see oscilloscopes always mentioned.
i see LC units mentioned
I see signal generators mentioned.
I have a good high end PC .(which I built).I have seen adapters for o/c plus LC etc that would do the job I suppose.
but can I use a very cheap oscilloscope (single trace 10mgz etc) to check /tune etc...these can be bought quite cheap.
I am a hobbyist electronic noob..( I can solder and chew gum..but not at the same time)!
any help thanks
johnno
Adelade south australia.

[Carl-NC]

You can squeak by with a voltmeter and a soldering iron, but if anything goes wrong, you'll probably need an oscope. Yes, a cheap one will do... I've seen basic solid-state oscopes for $50.

[johnno]

Thanks carl..even a single trace 10mhz scope?
I have never used one,so I guess it will be another learning curve.
I probably have most of the equipt (except 'scope and L/C meter).
Do many people out there use commercial coils instead of winding yer own?
Thanks again
johnno

[Charles (Upstate NY)]

You can pick up a decent scope on ebay for very little. Here's a BK Precision dual 20mhz for a buy it now price of $65. Thats hard to beat. I paid $75 for my used BK scope off ebay and gave it to a friend when I purchased my new scope. http://cgi.ebay.com/BK-Precision-Mod...QQcmdZViewItem

This is where I buy all my test equipment. New scopes start at $207 for a single trace, about $285 for a dual, Instek brand.

http://www.testequipmentdepot.com/

[Carl-NC]

Thanks carl..even a single trace 10mhz scope?

I suggest dual-channel, which most oscopes are. 10MHz min, but as Charles says, even 20-30MHz is cheap, so look around.

[Ray-NM]

More is better

If I could afford it I would have a 4 channel scope or maybe 2 dual channels scopes so you can watch what happens all along the signal path.
RayNM

[Elie]

What about including oscilloscope displays in metal detectors? I mentioned this before, and no one replied.

[Carl-NC]

If I could afford it I would have a 4 channel scope or maybe 2 dual channels scopes so you can watch what happens all along the signal path.
RayNM

This is where a digital scope is valuable. Or a PC-based scope.

[Carl-NC]

What about including oscilloscope displays in metal detectors? I mentioned this before, and no one replied.

Expensive, plus it would be very difficult to create a meaningful display. Ferinstance, a time-domain display (even a Lissajous pattern) would not clearly distinguish phases a few degrees apart. And, most people would not be able to interpret the display.

- Carl

[Elie]

Expensive, plus it would be very difficult to create a meaningful display. Ferinstance, a time-domain display (even a Lissajous pattern) would not clearly distinguish phases a few degrees apart. And, most people would not be able to interpret the display.

- Carl

Metal detectors would finally be worth the exorbitant prices charged for them!
What about a phase difference multiplier?
The idea is that, after getting several thousand signals, the user would learn how to interpret the display, just like learning to interpret the beeps.

[Elie]

Phase difference mulitplier?

[Carl-NC]

Not sure what you mean... It's not hard to measure the phase response of a target and display the number, detectors already do that. I just think that an oscope-style display makes interpretation far more difficult. Actually, I think the XLT/DFX phase spectrum meter is a good way to display phase response.

[Elie]

Those graphs just display the phase response at one moment in time. An oscilloscope display constantly changes. With a Lissajous pattern, you could really get a good idea of what you were detecting. Give it a shot.

[Carl-NC]

Those graphs just display the phase response at one moment in time. An oscilloscope display constantly changes. With a Lissajous pattern, you could really get a good idea of what you were detecting. Give it a shot.

Yes, but I don't think you could watch a Lissajous pattern and ever hope to mentally process it. As the target sweeps by the coil, the pattern goes from, say, a diagonal line to a diagonal ellipse. You would have watch the "peak" ellipse and try to figure out the phase from its shape... I don't think you can visually resolve 55 degress (gold) vs. 58 degrees (pulltab)*. I know I couldn't.

I've done this on the bench... a simple IB circuit directly feeding an oscope, and watching the Lissajous image. It's interesting, but not a practical display.

- Carl

[Elie]

Yes, but I don't think you could watch a Lissajous pattern and ever hope to mentally process it. As the target sweeps by the coil, the pattern goes from, say, a diagonal line to a diagonal ellipse. You would have watch the "peak" ellipse and try to figure out the phase from its shape... I don't think you can visually resolve 55 degress (gold) vs. 58 degrees (pulltab)*. I know I couldn't.

I've done this on the bench... a simple IB circuit directly feeding an oscope, and watching the Lissajous image. It's interesting, but not a practical display.

- Carl

Start with a circle.