slope of a graph

[shubhi]

Hello

I am trying to get the slope of a graph and the minimum threshold value (which leads to highest change in the slope of the graph) after getting the measured value from the instruments as shown in the pic attached.

Would be glad if someone can help me with this.

[James_R]

Would this function give you what you are looking for?

[shubhi]

Hi James

I am using LV8.2 and actualy could not see this option available there. 

There is no signal for "slope" there.

I used the Curve Fitting Express for getting the slope and it displays slope in the front panel while running and saves only the last slope measured.

I was wondering if there is any way where I could save slopes from all the point and not just the last set.

Thanks !

[P@Anand]

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@shubhi wrote:

Hi James

I am using LV8.2 and actualy could not see this option available there. 

There is no signal for "slope" there.

I used the Curve Fitting Express for getting the slope and it displays slope in the front panel while running and saves only the last slope measured.

I was wondering if there is any way where I could save slopes from all the point and not just the last set.

Thanks !

---

I guess you need to do some modification like bundling all the slopes together in a loop tunnel. Could you show the code what you have done then its easy to suggest a method.

[johnsold]

You could use the Savitsky-Golay filter to calculate the first and second derivatives of your data.  The detailed help for the filter VI has information on how to use it to take derivatives.  Note that the number of "side points" appears as a shift in the x-axis of the results, so you need to compensate when finding the point of maxiumum slope in your original data.

Lynn

[shubhi]

Hey Anand

This is my vi. I want to measure the slopes at all the points (and display on front panel )which I measure and stop the loop when the maximum slope has been attained. 

Thanks a lot!

[P@Anand]

You cannot find slope for each point you have take set points and calculate that and also you will have only one slope for a ramp and it will be the same wherever you take the points. You may find this useful

[shubhi]

Yes, I agree , so I just want to get that slope which has the highest change from the previous one.

[P@Anand]

No you are confusing. How does your singnal look like is it possible to show a picture of it.

[shubhi]

Here is the picture. Two curves shows the area I am interested at. The turn on slope by means of which I could find the minimum voltage level and then the slope of the ramp.