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counting of Triggerpulses

Question asked by VRFuser on Nov 11, 1996
Hi all,

I'm trying to do a program, which should count triggerpulses.
I'm using a ComputerBoards ADC and i get out an array of Measurement Values.
How can i look at each of the values whether they are over or under the
trigger threshold? The problem is that it must be very fast. We are sampling
at a rate of at least 48kHz.
But i think i should first give U a short discription of my problem.
We get some analog triggerpulses (not TTL) out of our Magnetic Resonance
Tomograph. I want to use these triggerpulses to regulate some patient
stimulating equipment. The pulses must be sampled at at least 48 kHz in
order to not missing any signals(they are very short in time!). There are
either 128 or 256 triggerpulses in a time range of 10 to 20 sec. After that
there is a pause of about 1 sec and then it begins again.
I want to count up the triggerpulses to a value of 128 or 256 and than start
a program  on my PC (or give out a signal on a dig. I/O) and stop it again
after the next 128 or 256 pulses.
Has anybody done anything like this before?
Another Problem is the output as a Graph or a file. When I sample with such
a high frequency i miss all values after about 3 to 8 sec.
I have a Pentium 120 MHz PC with 32 MB Ram an Win3.11. I tried to write the
File to a Ramdrive but that doesn't improve the problem really (only a bit).
The third problem is that I want to write the time scala to the file, too. I
wrote a program that calculates the time of each sampling but that takes (at
high frequencies) 10 to 20 times longer for each mesurement. Is there a
possibility to get the time directly (from the DAC f. e. ), and would that
be faster? 

I'm looking forward to hearing of you.


Bjarne Roscher

stud. Ing. (FH)

Haukeland Univ. Sykehus
med tek avd
N-5021 Bergen