topic Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)? in LabVIEW

How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

m@NI_forum — Fri, 04 May 2018 17:12:16 GMT

Hello,

I am scanning 10 resistors (measuring resistance) using a multiplexer card PXI-2503 and a soursemeter Keithley 2400. As I'm reading data one by one and from each reading create a cluster containing a channel, time, resistance value. Then every cluster is sent to a queue.

Queue is used to write data to a TDMS file and also I would like to plot resistances of all channels on a graph vs time. The question is how to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

Gregory — Fri, 04 May 2018 17:34:13 GMT

Hi m@NI_forum,

You can use an XY Graph. In a shift register, you will hold an array of XY graph data, which itself is a cluster of x-array and y-array. When you receive a new point, index to the correct XY data (using the channel #), add your new X and Y points to corresponding arrays, and reassemble your data.

You can use a nested "in place element structure" to access the array element and the cluster elements.

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

m@NI_forum — Fri, 04 May 2018 19:30:00 GMT

For some reason, I cannot find Build XY Graph VI in my palette. Is there a way to plot without using Build XY Graph VI? By the way, can I download Build XY Graph VI anywhere?

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

Gregory — Fri, 04 May 2018 19:53:44 GMT

You can create an XY graph without the express VI, in fact I'd prefer if you did!

Here is an example of building the plot one point at a time. Note that it is not an example of good programming practice (no errors, typedefs, queue release, loop stopping) it is just meant to get you up and running.

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

m@NI_forum — Fri, 04 May 2018 22:04:49 GMT

Thank you. Could you please write me the name of the tool? I cannot find it. Unfortunately, I cannot open your VI as I use an older version of LabVIEW.

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

Bob_Schor — Sat, 05 May 2018 02:47:14 GMT

The function is called "Build Array". It exhibits "polymorphism", changing its appearance (and behavior) depending on what is wired to its input(s). Drop one down on a Block Diagram and read its Help entry.

Bob Schor

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

Gregory — Mon, 07 May 2018 16:08:16 GMT

Here it is for LV 2012

Re: How to plot multichannel graph taking data from a queue (i.e. points of random channels one by one)?

m@NI_forum — Tue, 08 May 2018 07:29:58 GMT

gregoryj & Bob_Schor, thank you both for answers. They are helpful. The VI works now.