How to detect threshold crossing signal in Labview with NI USB 6008?

[Array01]

Hello Everyone 

Here I include the rar file used.
This program is used to detect eye movements based on the polarity of the signal. the polarity detected on channel 1 and channel 2 is the half-signal polarity.

eye activity that is detected looking up is when the eye from its normal position then looks up. but when looking back to the normal position, a signal will be detected as when looking down.

So, I want to combine 2 eye movements to make one command. this way I have to determine the polarity of the signal for the 2 movements. where the polarity will cross the threshold. like the following picture.

But i don't know how to detect the polarity if there's crossing threshold.

[Bob_Schor]

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@Array01 wrote:

Hello Everyone 

Here I include the rar file used.  No, there were no attachments.
This program is used to detect eye movements based on the polarity of the signal. the polarity detected on channel 1 and channel 2 is the half-signal polarity.  What are the two signals?  Horizontal & Vertical Eye position?  In what units (degrees, mV, something else?)

eye activity that is detected looking up is when the eye from its normal position then looks up. but when looking back to the normal position, a signal will be detected as when looking down. This doesn't make a lot of sense.

So, I want to combine 2 eye movements to make one command. this way I have to determine the polarity of the signal for the 2 movements. where the polarity will cross the threshold. like the following picture. This doesn't make much sense either.

But i don't know how to detect the polarity if there's crossing threshold.

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Some comments (from someone who has, in fact, recorded 3D Eye Positions in human subjects):

• What kind of eye movement are you recording?  Is it a saccadic eye movement?  Is it "smooth pursuit"?  Is it a result of a head movement (a vestibulo-ocular reflex)?
• I'm guessing that you are recording gaze, which i'll define as subject-induced 3D eye records where the eye position is relatively stationary in the 2D "Gaze space" (two coordinates describing the direction in space, sometimes called azimuth and elevation, of the center of gaze),  then makes a saccadic jump to another "Gaze Position".
  • Are you interested in the (relatively static) Gaze positions?  Do you want to describe them as a 2D position (in what I called "Gaze Space" or 3D position (taking into account that, to a first approximation, saccadic eye movements are single-axis rotations that can include torsional movements of the eye)?
  • Alternatively, are you interested in the saccadic eye movements that take the eye from one 2D Gaze Position in space to another?  Are you restricting yourself to single axis rotations (Left-right from a straight-ahead gaze, or up-down from a straight-ahead gaze), or the unique single-axis rotation to go from one Gaze Position to another (which requires a 3D "Rotation Vector")?

If the above questions seem unfamiliar to you. you may need to learn a little about rotatory movements of (spherical) objects.  Note that you can also say you want to study only horizontal movements involving the eye rotating about an earth-vertical axis, or vertical movements where the eye rotates in a vertical plane that includes the initial gaze position.

If this sounds too mysterious and weird to you (it can get even more complicated!), I recommend first solving the 1D problem of horizontal eye movements that start with the eye looking along an axis lying in an earth-horizontal plane that intersects the eye, with movements (or gaze positions) that remain in this horizontal plane.

Bob Schor

[Array01]

thanks for the response sir
Here I include the rar file used.
This program is used to detect eye movements based on the polarity of the signal. the polarity detected on channel 1 and channel 2 is the half-signal polarity. I will use this motion detection result as a command input for the device.

in this program, the polarity relationship with the command as shown below.

after I did some research, it turns out that eye activity that is detected looking up is when the eye is from its normal position and then looks up. but when looking back to the normal position, a signal will be detected as when looking down.
So, I want to combine 2 eye movements to make one command. this way i have to determine the polarity of the signal for the 2 movements. where the polarity will cross the threshold. like the following picture.