Ciro,
The first thing I suggest, is going to Settings >> Audio interphase and setting up your sampling parameters.
Suggested:
384 kHz - 16 Bits - left Channel
In the latest version of PRA 22 you may as well go for the highest sample rate 384 kHz even if your sound card is slower, the software does a good job of interpolating the samples.
Next, I think it is important to know the
pulse direction, pulse length and pulse height from your detector and spectrometer setup.
The pulse direction is easily identified from the
View >> Audio Input window (it is like a simple oscilloscope).
Then run the software with "Shape Tolerance method" un-ticked. and look at
View >> Pulse Width Histogram to identify and adjust your mean pulse width.
Once you have determined the pulse width, say for example 75 µs. you can open the
Settings >> Pulse shape editor and adjust the number of samples you want to use.
i.e. say you are sampling at 384 kHz then;
\[ (1 sec /384000 kHz = 2.6 µs) \]
So there will be 2.6 µs between each sample, so to capture the 75 µs pulse you will need a minimum of 30 samples to capture your pulse , and I would allow for a bit of space either side and round it up to 40 samples.
PRA now has up to 60 samples and the pulse peak always sits in the middle at around the 30th. sample, so if you want to sample with 40 samples, you need to untick samples 1 to 10 and 50 to 60, leaving the samples 10 to 50 ticked, giving you a window of 2.6 * 40 = 104 µs. wide.
Keep in mind that the sample window size affects your dead time, so with a sample window of 100 µs the maximum count rate will be around 3000 cps.
There may be a more scientific way to calculate this, but as a rough estimate I use;
\[ Max Count Rate = (1 sec) / (window size) * 3 \]
If you need to push your count rate higher, you can narrow down the sample window.
Once you are happy with the settings you can tick the
Use shape tolerance box and start recording.
Hope that makes sense..
Steven
PS: Latex Math was used in this post.
It's easy just start and end your expressions
with
backslash squarebracket like this;
(ignore the Latex button in the editor.)
- latex.png (6.13 KiB) Viewed 5334 times
looks like this..
\[ a^2 + b^2 = c^2 \]
