field point replacing simulate signal problem

[twseb]

Hi,

I have been doing a simple code to display waveform on a graph. I was supposed to be using a compact fieldpoint instead of simulate signal, however as i does not have the compact field point back then, I proceed to do the code using simulate signal. The graph did show the waveform. Recently I tried replacing simulate signal with a fieldpoint input, the waveform did not show on the graph...The graph is in autoscale for X and Y axis. What did I do wrong? Is there any way to overcome that problem?

Thanks for any help

Sebastian

[Jesse_O]

Hello Sebastian,

I suspect the problem you are seeing is related to the different data types that comes out of the Simulate Signal Express VI and the FieldPoint VIs.  The Simulated Signal Express VI allows you to specify how many points you want returned to your application.  For example you can specify to receive 100 points a sine wave with a frequency of 10.1 Hz where you sampled at 1KHz.  In this situation you would acquire 100 points and graph them.  If you then switch over to use the express or standard FieldPoint VIs, they return a single point.  If you try to graph a single point it appears, however it shows up right along your axis and is hard to tell that anything is graphed. 

The above assumes that you are using a waveform graph to display the data.  If you change this to a waveform chart it keeps a history of data points and you can send a single point to the graph at a time.  For example if you send 1 point at a time to a chart 100 times, you will see 100 points.  This is different from the graph because the graph will only display what you send it (with no history).

If you are using a waveform chart, and you are still having problems, can you confirm with a probe or highlight execution that you are getting data back from your FieldPoint controller? 

If you determine that you are having problems reading data from your FieldPoint controller, are you able to configure and read data from your controller through Measurement and Automation Explorer (MAX)?  If you are getting errors in LabVIEW when executing your code, what is the error and where is it occurring?  Finally, what FieldPoint controller, modules, LabVIEW software and driver versions are you using?

Regards,

Jesse O.
Applications Engineering
National Instruments

[twseb]

Hi Jesse

Thanks for clearing my doubt, it seems to me that i need to do a VI that aqquires the number of sample I want. I am able to configure and read data through MAX. Currently I am using cFP-2120 controller with a strain gage module, and LabVIEW 7.1. Regarding the code, there is no error generated.

Sebastian

[Jesse_O]

Hello Sabastian,

The FieldPoint VIs always return a single value.  You can however keep a history of your data by creating an array of that data or by using the waveform chart.  If you need a larger set of data for processing (i.e. filtering) you will need to build an array of data.  Since you are able to acquire data in MAX, and are not getting any errors in MAX everything should work.

Please confirm that you are getting correct data in LabVIEW (even if it is one point).  Once you confirm this you can start to either build an array of data or use the waveform chart to display a history of data.

Please let me know if you have any problems with this.

Regards,

Jesse O.
Applications Engineering
National Instruments

[twseb]

Hi Jesse

I have use a vi that someone had created to plot the graph with the fieldpoint. Currently I am able to complete my task and saving the results in LVM file. I have yet to try it on my fieldpoint in Real-Time, will post my problem if I encountered any. Thanks again for your help.

Sebastian