Limit Testing VI Explanation

[dave56]

I am fairly certain that what I am trying to do is clearly done in the "Limit Testing for Unevenly Sampled Data Measurement VI" example. However, I am not quite sure how it is working. I don't quite understand what the values inside the Upper and Lower Limit Specification Cluster are. They don't meet exactly at their specified values, so when they are fed into the Limit Specification for UnEvenly Sampled Data what is it doing to the data?

This VI is somewhat what I would like to do in my own application. Basically I have several excel files that contain X and Y values and I graph them out. Next I'd like to set alarms to indicate areas of interest. This is where I'd like to implement something such as this example VI. Another question I hav
e about the VI in the example, when they are constructing their waveform, not only do they wire in the Y values, they also worry about the dt and t0 values as well. Since I only have the Y values, is this something that I have to worry about as well?

Thanks for any help or hints.

[Ankita A.]

Hi,

The X values inside the upper and lower limit specification cluster define the interval in which you want your limits to be applied. The Y values inside the upper and lower limit specification cluster are used for interpolation. To illustrate how the "Limit Testing for Unevenly Sampled Data Measurement VI" works, lets use the numbers in the example program and see how high limit curve is plotted.

Based on the numbers in the example
X_high Y_High
6 1
11 0.8
16 0.5

X values of signal between the lowest and highest values of X_high (i.e. between 6 and 16)are
6.7
9.0
11
13

Now this VI is finding the y values of high limit corresponding to x values 6.7,9.0,11,13 using interpolation. So in the XY graph, for the
high limit, you see four points corresponding to
x = 6.7,9.0,11,13. Similarly since the Lowest and highest values for low limit are also 6 and 16, so for low limit curve, you see four points corresponding to
x = 6.7,9.0,11,13.


About dt and t0 values, you need to wire a "-1" to dt and t0 should be equal to the first value in the "X values for signal".

Regards,
Ankita A.

[Alv]

Where do I find the example above..."Limit Testing for Unevenly Sampled Data Measurement VI"

R/Scott