Surf Pro Kit

[waltr]

Thanks but that part is done. In just looking to figure out how to measure the pulse delay just to know where I'm at.

As on all PI detectors use Two channel scope.
Ch1 trigger on TX pulse off.
Ch2 on the Sampling pulse.
Measure on scope time between.

[Wahyu]

Here is an example of the type of targets you eliminate as you increase the delay.

Hello 6666,

I have been test at my MD, if delay 20uS , my 1 gram gold ring, cannot detect,

What kind gold ring at table list?

[Tibuck19]

Thanks but that part is done. In just looking to figure out how to measure the pulse delay just to know where I'm at.

Its not that complicated! connect your coil, use a few coins like a nickel and pennies also a ring if you plan on finding said items, wave it over the coil and keep tuning the delay up till you have the best results, and that the coil does not beep from its self when swinging it! I might be wrong bet there is no right and wrong delay, slow delay will let you find one thing and fast another, you just need to find happy middle for what you plan, heck you can even wire in a 100K external Pot and
adjust as u go .

[dime196604]

Its not that complicated! connect your coil, use a few coins like a nickel and pennies also a ring if you plan on finding said items, wave it over the coil and keep tuning the delay up till you have the best results, and that the coil does not beep from its self when swinging it! I might be wrong bet there is no right and wrong delay, slow delay will let you find one thing and fast another, you just need to find happy middle for what you plan, heck you can even wire in a 100K external Pot and
adjust as u go .

I dont think you understand what I am asking. Delay is set already and in happy with it. What I was aking was how to measure it. Thanks to everyone else for the fast response. I will let everyone know how it turns out when done.

[Tibuck19]

I dont think you understand what I am asking. Delay is set already and in happy with it. What I was aking was how to measure it. Thanks to everyone else for the fast response. I will let everyone know how it turns out when done.

Please don't be insulted by this, but we do all understand what you are asking, however it is very clear if you have an oscilloscope, you are not sure how to use it, to measure time base, which in terms will give you the Delay uS measurement's. which is why I suggested the Back to basic video. Trust me I am no electronics Guru, I know how it feels like to be new to electronics, and trying to piece all the information together.

[dime196604]

Please don't be insulted by this, but we do all understand what you are asking, however it is very clear if you have an oscilloscope, you are not sure how to use it, to measure time base, which in terms will give you the Delay uS measurement's. which is why I suggested the Back to basic video. Trust me I am no electronics Guru, I know how it feels like to be new to electronics, and trying to piece all the information together.

Not at all insulted. Your replys are helpful , just were not the ones I was looking for. I kept asking about measuring the pulse and it seemed like you kept telling me just to tune it and it dont matter where it is. When I was just asking how to find out what thr delay was, not to adjust it. But all is good.

[Polymer]

Hi dime196604,

Hmmm, I don't know the surfxx!? Maybe you can post a picture of the board.

Just read more thoughrougly and see you have only one channel on oscilloscope. That's a bummer, but not the end of the world.
I am posting a screenshot of surf PI signals of PIN6 5534 & PIN10 4093 so you can see the time/voltage adjustments you
approximately need. The yellow one is the delay time.
I would suggest probing the pins of the 4093 whilst adjusting the delay pot, you'll see the yellow part getting longer/shorter.
This is of course assuming the surfxx is built in a similar fashion.

Good Luck!

[dime196604]

Hi dime196604,

Hmmm, I don't know the surfxx!? Maybe you can post a picture of the board.

Just read more thoughrougly and see you have only one channel on oscilloscope. That's a bummer, but not the end of the world.
I am posting a screenshot of surf PI signals of PIN6 5534 & PIN10 4093 so you can see the time/voltage adjustments you
approximately need. The yellow one is the delay time.
I would suggest probing the pins of the 4093 whilst adjusting the delay pot, you'll see the yellow part getting longer/shorter.
This is of course assuming the surfxx is built in a similar fashion.

Good Luck!

[ATTACH]44315[/ATTACH]

So if I am reading that correctly, your delay is at about 10us in the pic?

[dime196604]

First thing you need to do is tightly wrap you lose bundle of wire to make it a coil, you can not tune your detect with your coil that way, Second task is to watch this https://www.youtube.com/watch?v=OQMnjaMSKn8 , it will teach you how to measure time with your oscope , which then , you will know the delay pulse you are setting the detector too. Another thing that will help you understand more, Which was suggested to me , and was very helpful is, Buy the book Inside the metal detector written by Geotech very own Carl and George. https://www.amazon.ca/Inside-Metal-D...metal+detector

What's funny is the scope in that vid is the scope that I own. Just never been able to get channel 2 to work. I traded a old Realistic TRC 40ch SSB base radio 📻 for the scope. Got started in the radio hobby when I was young and broke, so I bartered a lot.

[Tibuck19]

What's funny is the scope in that vid is the scope that I own. Just never been able to get channel 2 to work. I traded a old Realistic TRC 40ch SSB base radio  for the scope. Got started in the radio hobby when I was young and broke, so I bartered a lot.

You can turn on the second channel with a either a dial or a switch, Im sure someone in here has the tektronix 465b and they can walk u throw it.

[Polymer]

So if I am reading that correctly, your delay is at about 10us in the pic?

Yes.

Perhaps the following can help with only 1 channel measurement, just came across it. See the 3rd paragraph.
Have observed this phenomena myself, was thinking it was an oscilloscope artefact.

Copied from Post #17 http://www.geotech1.com/forums/showt...=measure+delay

"Hi Bob,

Do you have a dual trace scope? You can monitor TP1 and TP2. One will be the output of the preamp and the other will be the delay pulse. You can measure the delay from the beginning of the pulse from the preamp to the fallling edge of the delay pulse. Adjusting your delay pot will shorten or lengthen your delay pulse.

The falling edge if the delay pulse will be somewhere on the decay curve. This should be your delay. Your decay curve will most likely have a flat spot on top, caused by the diodes clipping the flyback signal. If you can decrease your delay until it hits the flat spot on your preamp signal, your detector will stop resonding. This is your minimum delay setting.

Now if you DON'T have a dual trace scope, you can take advantage of the imperfections in the design. Look very closely to the output of the preamp and you will see as small blip in the decay curve that changes with adjusting your delay. That will coincide with the falling edge of your delay signal (neat huh!?).

I'm not near my scope this week, so I cannot post any images.

Hope this helps.

Don"

Good luck! Polymer

[dime196604]

You can turn on the second channel with a either a dial or a switch, Im sure someone in here has the tektronix 465b and they can walk u throw it.

No. I'm sure it's dead. I can get a trace on channel two but that's it. Think it might be a connection issue on the backside of the panel. I opened it up once but That's way too much for me. Way too much stuff going on inside that for me.

[waltr]

Now if you DON'T have a dual trace scope, you can take advantage of the imperfections in the design. Look very closely to the output of the preamp and you will see as small blip in the decay curve that changes with adjusting your delay. That will coincide with the falling edge of your delay signal (neat huh!?).

I see this on the PI detector I have built and is a way to see and measure Sampling delay.

No. I'm sure it's dead. I can get a trace on channel two but that's it. Think it might be a connection issue on the backside of the panel. I opened it up once but That's way too much for me. Way too much stuff going on inside that for me.

There should also be an External Trigger input on the scope. I have a two channel scope and use the external trigger from the TX pulse then have two channels to measure two other parts of circuit.
You should be able to do the same thing.

[dime196604]

Found this in another post. Would this method be better at setting the delay? I've set the delay by ear with a gold ring, but came across this and wanted to know if it was better.

This is a direct copy of what was posted in a different thread.




With this fixed, next is minimal delayadjustment, first sample must start as soon as possible. Easiest way is tomonitor integrator output (first half LM358 after analog switch, pin 7 onsilverdog PCB). Will be about zero, or less than volt in any direction atlonger delay setting. Now decrease delay, pot and trimmer and observe voltagechange, at shorter delay it will start to rise, at one point will reach some3.8V saturation, chip is unable to output more, and detector will stopresponding. Increase delay a bit and this is speed limit for coil used, fewhundred mV or so less than saturation point. This output is very sensitive,less than mV of change will trigger audio when metal is detected.

[waltr]

That is a method to find the MINIMUM Delay that could be used.

In real practice this is probably not the best delay value for a wide range of targets.
I like to increase to delay a little bit from minimum to have a bit of dynamic Voltage range on the integrator output.

This method would work to put a mark on the Delay setting dial of the minimum delay.
This will also change with a different coil/damping resistor.

So try it then check various targets and then use in real conditions.