Graphing Encoder Counter Input in LabVIEW Signal Express

[Shreve]

In LabVIEW SignalExpress, using a simulated daq system with a counter input, I set up a DAQmx Acquire of an Angular measurement based on a quadrature encoder.  Acquiring N samples, I acquired a table of measured values.  I would like to plot the results, however, I am not given the option to view the data in any other format.  I can plot if I acquire one sample, but that does not allow me to sync the data with the analog input signal I would also like to acquire and view.  I had to use an external clock to take the encoder data, so the data is acquired a double datatype.  I would like to be able to view in realtime, encoder position with respect to time.

[Jeff_T.]

Hi Shreve,

This was reported to R&D (# 478FEO4E) for further investigation.  If your application allows, you can set the acquisition mode to 1 Sample (On Demand).  This will allow you to select a Chart Display.

Thanks for the feedback!

Jeff Tipps
Applications Engineer
National Instruments

[lizardo]

I have this hardware:

Scc-ctr01 + scc-sg24 +scc  68 I/O module slot + PCI 6220 + signal express

I have a electronic dynamometer with an incremental encoder (scancon, 2RMHF) and a load cell,

And, I need representing the position in millimeters of the load cell vs the force in newtons.

For now, the signal of the encoder is applied in a counter. When I need to know the final position of the load cell, I must reset the counter and start the process, and later, I stop the process manually and the position is registered in a counter, and the force in a printer.

I don’t find any help in program about this, please help me.

Thank you very much

Best regards

[Paul_C.]

Hi Lizardo,

It sounds like you are going to be needing a counter task for angular position to aquire the position from the encoder.  In addition, you will require a task that will measure the voltage from the load cell.  This can be applied to a custom scale to find the force in Newtons.  This can all be managed with through steps within LabVIEW SignalExpress.  I'm not sure if I understand how you want the counter to behave after it gathers the final position of the load cell.  You could take the value of the final position and then setup a new task / step in LabVIEW SignalExpress to reset the counter and restart your next process. 

If you're unsure on how to do this within LabVIEW SignalExpress, I would recommend looking at our getting started with LabVIEW SignalExpress guide.  This can be found by going to Help » Getting Started with » LabVIEW SignalExpress.  I would also recommend taking a look at the LabVIEW SignalExpress Help (From within SignalExpress, this can be found at: Help » LabVIEW SignalExpress Help).  This is a great resource for learning the functionality of LabVIEW SignalExpress.

I hope this helps,
Paul C.

[lizardo]

HI,

I want to obtain of this combination of hardware and software a system that  allow me acquire a signal of the load cell and the counts of the incremental encoder’s pulses  and represent in a graphic the force vs the distance.

 The distance is pick up to a incremental encoder in a worm gear that with its movement, move a load cell in a base. the reading of the position is in millimeters.

In this moment, I can only represent the force, the position is only visible in a display, I want to take a samples of  the force and the count in millimeters, ten or more times per second and perform a graphic in a real time.

Thank you for your answer

Best regards

Lizardo Laguna

[Paul_C.]

Hi Lizardo,

I don't see a way to take an analog input (with a custom scale) and graph it vs. a counter input (counter tasks cannot be applied to a custom scale although this can be done with post analysis) as you require in real-time.  However, you can extract the information from LabVIEW SignalExpress to a spreadsheet file.  This would allow you to take the data and scale it to be graphed within a spreadsheet program.  I understand this would not be a real-time display, but you will still be able to read both the force of the load cell (scaled from your voltage input) and the edge counts seperately in real-time.  After the program is finish, you would be able to extract the data to be plotted in a spreadsheet file.

I hope this helps,
Paul C.

[lizardo]

Hi

Ok, I understand that I can export to spreadsheet the data of the force and the data of the position (the account of the pulses of encoder) and perform a graphic in function of the time?.

If it is really, is ok for me. My principal fear is don't   perform this graphic because is important to know in every cycle of data acquisition, the force and the position.

This kind of graphic allow to know one force in some tensile percentage before of the sample can be broken ,  this test is used in different materials like rubber, leather, etc.

Best regards