My Surf PI 1.2 sample width vs. ITMD example has me confused - what am I missing?

[Polymer]

I've had my oscilloscope for a week now and have been looking at many curves on the Surf PI 1.2
and trying to make sense out of what I'm seeing.

In this case I'm looking at the sample width (Pin 3 U4), which seems to be around 40us.
A lot of that covers the flat part of the decay curve.

That's not what I can see in ITMD 1st edition on Page 153.
The sample width there is during the curvy part.

Am I measuring/interpreting wrong, is my Surf PI somehow out of whack?
Can anyone give me a pointer here?

Here's two screenshots put together: TP1 & TP2 & pin3 4093

[kosacid]

i use pin6 on the ne5534 and pin13 of the 4066

[Qiaozhi]

I've had my oscilloscope for a week now and have been looking at many curves on the Surf PI 1.2
and trying to make sense out of what I'm seeing.

In this case I'm looking at the sample width (Pin 3 U4), which seems to be around 40us.
A lot of that covers the flat part of the decay curve.

That's not what I can see in ITMD 1st edition on Page 153.
The sample width there is during the curvy part.

Am I measuring/interpreting wrong, is my Surf PI somehow out of whack?
Can anyone give me a pointer here?

Here's two screenshots put together: TP1 & TP2 & pin3 4093

[ATTACH]40539[/ATTACH]

Your sample pulse width is ok.
You should also read page 154 of ITMD, especially note 13 at the bottom. The figure is showing a narrow sample width of around 10-15us to make it more sensitive to small gold targets. For coin hunting (e.g. at the beach) a wider width is more useful. Remember that the edge of the received pulse moves along to the right in the presence of a target.

[Polymer]

i use pin6 on the ne5534 and pin13 of the 4066

Pin 6 5534 = TP 2
Pin 3 4093 = Pin 13 4066

Thanks anyway!

[Polymer]

Your sample pulse width is ok.
You should also read page 154 of ITMD, especially note 13 at the bottom. The figure is showing a narrow sample width of around 10-15us to make it more sensitive to small gold targets. For coin hunting (e.g. at the beach) a wider width is more useful. Remember that the edge of the received pulse moves along to the right in the presence of a target.

OK, got it. Thank You!