Hi there,
Many thanks for replying to my post.
I have just attempted to go through your instructions, but our version
of Labview is version 7, so your example code won't open. A couple of
the procedures were different as well..
I have not quite understood the exact idea of what your instructions are going to do. For instance what is MAX?
Perhaps if I relate more clearly what I need to do it will help me!
So, our setup has 4 input channels wired up to the input interface: ai0, ai1, ai2, ai3.
The first three are already used for recording relevant signals.
Channel ai3 is 'free', and I was hoping to use this to trigger the
other channels to record their signals. The input to this channel would
be a downwards going edge from a Berkley trigger box. There would thus
be a certain period of time whilst this was at a negative voltage,
before it returned to a zero level again. At the moment I want to use
the initial downwards going edge to trigger the recording to start, and
the either the following upwards edge or another downwards edge to stop
the recording. So, I think I'm using the trigger to stream..
What would be really great would be if there was a way to set the
system to capture the 3 input channels for a certain number of
repetitions of the trigger pulse. So for example, let's say:
downward going edge trigger input detected, recording starts
upwards going edge goes by, but recording continues for now
new downwards going edge goes by, recording continues for now
another upwards going edge appears
another downwards going edge appears, and recording is stopped.
So, in total the system has detected an initial downward edge and begun
to record, and it has been set up to cease recording when it detects
the 3rd instance of the downwards going edge (in actual fact it would
be fine for recording to be stopped either by the 3rd downward edge, or
the 2nd upwards edge - whichever is simplest).
Now I've got that off my chest, let's try a couple of questions..
I don't really understand from your instructions which channel I'm
setting up to detect the triggering pulses. Does it matter that we only
have these 4 analog input channels, and we want to use a digital
triggering edge on one of them? You say "Highlight your channels", but
I thought that the recording VI that I posted was what I would use to
actually capture the input signals. I 'thought' I just needed some kind
of application that I would wire to this VI that would trigger its
recording.. Perhaps this is what your instructions do say, but it's
frustrating because I'm a complete amateur at this and I wish I was
more intuitive with it all..!
🙂
I don't think I need the channels to be read iteratively. I just need
them to record until stopped in the manner I described... hmm.. not
sure about that one...perhaps I do..
Again, we really do appreciate your help. The labview expert in our
department has left and we can't get hold of him so things are a little
desperate!
Many thanks,
Mike
