measuring distance between two points on a graph

[errcricket]

greetings.

i would like to perform some simple subtraction. i am using a ni sub-6210 (w/ SignalExpress) to measure the voltage output from a fluoremeter. i would like to know the change in voltage from one point to another on the graph. very similar to the "info" window in photoshop where you move the cursor over a certain area and it will give you the coordinates, i would like to move the cursor over a particular point on the graph and be able to get the voltage at that particular spot. image programs have a "measure" or "ruler" tool which measures will give you the difference when you select two points.

if someone knows how to do the latter - great. but i would be equally satisified to be able to know the y-coordinate by moving a cursor over a graph.

thank you and regards,

 - c

[GerdW]

Hi c,

the graphs have property nodes to read the actual cursor positions!
Just read one position, store it in a shift register, read next position and subtract... Distance z is sqrt( (x1-x0)^2+(y1-y0)^2 )

Btw. I would prefer to use 2 cursors for this purpose (in the picture are 3 cursors, but the first two are used for measurements/calculations left to the graph):



Message Edited by GerdW on 01-29-2008 03:38 PM

[errcricket]

GerdW,

thank you for your response - it is spot on. unfortunately after speaking with a ni rep, i don't believe i will be able to do this with just SignalExpress. thank you for taking the time to answer my question.


regards,


 - c

p.s. how do i rate your response


Message Edited by errcricket on 01-29-2008 10:05 AM

[Chris_K_]

Hi errcricket

Thank you for using our discussion forums.

You can access the curser functionality in LabVIEW SignalExpress by dragging the desired acquisition into a data view window, then right-clicking and selecting Visible items>>Cursors.

 

This will bring up two sets of vertical and horizontal lines along with a status window with cursor information.  As shown above.  You can move these lines to particular points on the acquired data and the values in the status window will update and relay the information that you are looking for. 

Chris_K

Message Edited by Chris_K_ on 01-30-2008 01:53 PM