Continuous data log and plot curve

[won_chulupa]

Hi, I'm new to Labview and currently in the learning process.

I have a load cell (LC105-500) and an A/D converter (D1521), both purchased from Omega.com. This allowed me to connect straight to the computer via RS232 and then from RS232 through USB. I did get Labview talking with the loadcell using the sample programs within Labview (basic read/write).

What we will be doing with the load cell is measuring the tension in a v-ribbed rubber belt on a rotating steel pulley. One end of the rubber belt will be attached to the load cell and the other end will have a dead weight. The load cell will be fixed to the wall. When the pulley is rotated, it will create tension in the belt. Basically, we're investigating the friction between rubber and steel and in order to do that we need the tension force on the belt. See picture below:

 

Ultimately, I'm asking for a simple .vi diagram (I think that's what you call it) that will datalog continuously for a short period of time (maybe 10 seconds), as well as a plot curve if possible. Again I'm only a beginner with Labview, any kind of information will be helpful.

Thanks in advanced.

P.S. This is the plot curve we're expecting after the test:

 

[bo200008]

It depends on how fast is the sampling rate. If it is not so fast (<100 samples/second), then maybe you can use a polling acquisition in a timed loop. Buffering the data in an array and save it after done.

[mishkin]

Hi won_chulupa,

What are you able to do with the VI at this point? It sounds like you can request the value of the load cell and read the current value back. To read these continously, you'll need to put your code in a while loop. You can also easily write the values to a file (text or TDMS - there are examples of how to do both in the example finder), and/or store them in an array in Labview. As far as the plot of the values, do are you simply looking to display the plot of points on the front panel of the VI? You can do this by wiring your values to the waveform chart. One thing here though: when communicating over RS232, you usually read back values in the string data type. To wire these values to the waveform chart, you'll have to convert them to numeric values - use something like a "decimal string to number" VI or "frac/exp string to number" VI in the string/number conversion palette.