How to see graph with labview web service

[ynse]

Hello everyone,

Im currently looking into the web services option of labview 8.6. I've seen some of the simple examples that can be found here on the site of NI. But these examples usualy deal with static data. Like the sum example, you enter your parameters in the URL and the result is displayed in your web browser.

What i would like to do now is display a graph in my web browser that show's a moving signal. But i'm having a hard time realizing this. How do i make this work? Do i need AJAX, Measurement studio? or is it enough just to use the labview web service.

Best regards.

Message Edited by ynse on 05-25-2009 06:36 AM

[Baji]

have a Look on this thread http://forums.ni.com/ni/board/message?board.id=170&message.id=400151#M400151

[ynse]

Hi Baji,

 

Thanks for the link, it's almost what i'm looking for 🙂 The principle is ok but i like to do this with the Web services, not with the web publishing tool and its remote panels. The thing with remote panels is that you still need to install the LV runtime engine at the client side, when using web services you don't need the runtime engine. Or am i wrong?

Example: http://zone.ni.com/devzone/cda/tut/p/id/7350

In this case they use adobe flex to display a wavefrom based on streaming XML data. I would like to do the same (create and display a waveform) without adobe flex. That's why i was thinking i might need measurement studio and AJAX. Or am i asking something that is not possible? 🙂

[NathanK · Accepted solution]

ynse,

You are correct that web services do not require the run time engine to be installed on the client. Unlike remote panels which render the VI on the client, web services do nothing with the client at all. The web service simply executes on the server and returns some data to the client. The client can render the data however it wishes.

Your question about measurement studio and AJAX is really asking about the client end. You can definitely use AJAX controls that update themselves with data that they acquire from a LV web service. A graph, however, would be extremely difficult as javascript does not yet have drawing capabilities.

The web graphs that I have seen do one of the following:

- "Draw" the graph points using HTML elements positioned with javascript. This is complicated, would be hard to getting working on all browsers, and would have severe performance problems with large data sets.

- The web service returns an image of a graph that the client refreshes. This takes more bandwidth than necessary and the server has to be able to take a snapshot of the graph. (LV real-time cannot use this approach.)

- The graph is rendered using a plugin for the browser. There are many technologies that can be used to do this: Java, Flash, Silverlight, etc. The example you referred to used Adobe flex which is a valid approach that you should not be quick to reject.

Measurement studio is not my area of expertise and I don't know what it can provide for creating a graph. Whatever it provides is likely making use of one of the approaches above.

Nathan

[ynse]

Hi NathanK,

Thanks for your reply, giving the 3 options you provided I think i will look deeper into the "plugin" method. Let's see if i can make something nice out of that 🙂

Best regards,

Ynse