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Offline Gwil
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« Reply #20 on: May 19, 2013, 03:39:53 pm »
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Hi Xavier

A metal object should cause a change in amplitude and/or phase of the sine wave at the output of the first amplifier, but the change might be very small, too small to observe on a scope.  (Also, the larger the signal present with no target, the harder it is to see a change.)  The TGSL uses loads more gain in the following stages to get an audible indication.   Your schematic in post no.12 didn't show a sync. det. stage, and you have a much better chance of seeing something worthwhile if there is one included.  Without one, the second amplifier is pretty useless as it can't handle 14.5kHz. 

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Gwil


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Offline xavierTopic starter
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« Reply #21 on: May 19, 2013, 03:59:40 pm »
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OK now that makes sense thanks Gwil I will make a third stage tomorrow, if I get back from the hospital before dark if not I'll do it some other time. I'll keep you posted on this one

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Posted on: May 19, 2013, 10:58:29 PM
Think I'll try a spice simulation first LOL

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So many questions so little time

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« Reply #22 on: May 19, 2013, 04:38:07 pm »
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Come to think of it, if you have a working TGSL it might be easier to open it up and probe it with the scope while showing it a target.  But you might not want to risk rendering it non-working...

Gwil


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Offline xavierTopic starter
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« Reply #23 on: May 19, 2013, 04:59:28 pm »
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Quote:Posted by Gwil
But you might not want to risk rendering it non-working...

Well it's not only that, I'm playing around with some digital stuff (PIC) and I need an input signal for it. All that I want is to see if my program will respond to the amplitude and phase shift and if it does then I will seriously get into the rest of it. The first tests that I did worked 100% the biggest problem that I can see at the moment will be stability but I have a pot to adjust the sensitivity ie a range for fluctuation. Hope this makes a bit of sense

HH
XAvier   


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So many questions so little time

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