Creating GUI interface for cof

[johned]

I am attempting to create a GUI interface on Labview that will read the measurements from a load cell ( Futek model L2331) that is connected

through a DAQ interface and  will output Coefficient of friction measurements vs time.  I would also like to be able to save the data to a file (eg...excel). 

Can anyone help me out with this?

JC

[WNM]

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@johned wrote:

I am attempting to create a GUI interface on Labview that will read the measurements from a load cell ( Futek model L2331) that is connected

through a DAQ interface and  will output Coefficient of friction measurements vs time.  I would also like to be able to save the data to a file (eg...excel). 

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As far as the saving of data to an Excel file goes, you can use the "Write To Spreadsheet File" function on the Files pallet to easily create a ".csv" file which can be read by Excel.

If you want to write the data directly to an Excel spreadsheet then this post has pointers to a couple of other posts that point to a library for doing so and an example of how it is done.

[johned]

Thanks Warren Massey,

Do you know about how to construct the GUI for reading the measurements from a load cell? If I use the DAQ Assistant will the output for the load cell come out as a strain measurement and if so how would I convert this into coefficient of friction measurements?

JohnEd

[Conseils]

You need to calibrate the input load on your DAQ system (with known values of load.. weights) to arrive a calibration factor for your system then :-

Worry about differentiating between static and dynamic friction.....
This should help a little, nice diagrams too.... here you sould be able to use these as the basis for your GUI or at least some basic ideas.
The link includes the math you need as well.
http://www.tribology-abc.com/abc/friction.htm

[johned]

OK,

But after I calibrate the input load and I am trying to construct this GUI in LABVIEW, what will my input for the DAQ assistant be? For example when I use the DAQ assistant it will prompt for different inputs (voltage, strain, etc).  I figured since it is coming from a strain gage, it would be strain.  What will I have to wire the DAQ Assistant node to in order to get my COF measurements as outputs?

[Conseils]

What I suspect you need, more for comparison than anything else, is the Force in Newtons not the strain in µ strain.

So one technique is to leave the input in volts and then figure out how many grams of weight gives how many volts from the load cell, and applying the necessory factors to give the force in Newtons unless of course your working in Christian units (lbs force).

Either way, strain or volts you are going to have to calibrate the input. Unless the factors are all ready supplied. to arrive at the following

"The coefficient of friction is simply µ =  F_spring /F_normal =  F_spring /(m_{block ·}g ), g=9.81 m/s²"  Notice that there is no mention of strain here but force.

Strain is defined as: - "The relative deformation of an object subjected to stress. Hence, strain is dimensionless."


Don't forget to get the sense of compression and tension correct for the displayed units.