Are you trying to detect the transitions as you collect your data or with the completed data set? If you are testing while collecting, a fast transition will give a large derivative. By subtracting the last 2 values, you should get a large difference when you have reach a transition, with the sign proportional to the direction of the transition. This could also be done on a completed data set by shifting the entire array by one position before subtracting, but you would be dealing with 2 copies of your data set.
On the other hand, if you used threshold array.vi, after detecing the first transition from 0 - 10V, then invert your data by subtracting the it from 10V and start checking for the threshold at the next point. By inverting your data after each identified transition, you keep the values you are searching below the threshold value until the next transition.
