waveform graph DAQmx read

[me.yet.not.me]

Hi guys, I have posted this earlier but cant find my post anymore so here it goes again...

I am implementing a chart recorder system with a 1kHz sampling rate that is to run continuously for at least 2-4 hours based on the Cont-Acq-and-Graph-Voltage-Int-Clk.vi, . Having difficulties with the DAQmx-Read (analog wfm 1Chan Nsamp) and Waveform Graph area; have searched for answers but still cant solve it completely..

1) Turned on scrollbar for Waveform Graph, but nothing is scrolling when it's running.  How can I make that happen?  I know waveform chart can give me that option nicely, but I need to have cursors that's why I am using waveform graph now.

2) Attempt to change the x-axis to reflect real time data, able to manual change the axis to agree with what's on the 'scope but if i change the multiplier the axis change, graph does not. I need a more versatile way.  Say 1kHz sampling rate should give me a time interval of 1ms.  I tried using array and XY Graph and worked, but I am stuck on how to incorporate that with Wfm datatype in DAQmx Read since the program is sampling on the same time while I'm building my array using t0 and delta t.  On the same time, I'm worried that using array would slow down the program run...

3) Is it possible, and how, to put in an annotation by just one button? (e.g. put tags on graph while running) I know annotation list property is an array, and want to double check..so if I want to access one of the element, I have to index-array myself to that element and change it there? since annotation does not have a drop-down list in property node, unlike in cursor where a property node with all the element can be listed in front of you.

I'm new to LV8, so please any help would be great!

Thanks!
Perry

[Dennis_Knutson]

First of all, every time you do an acquisition with that example, you get a new waveform that gets written to the graph. It is simply overwriting the previous acquisition. Your graph is probably set to autoscale and with no history data, the scrollbar is not visible because you have no history to scroll through. You can writ to a shift register and append new data to it with each iteration but if you want this to run continously for 4 hours with 1000 samples/sec, you will soon have an array of samples that is too large to keep in memory. Instead, you might want to write to a file as you acquire it and then write a program to view it later. Your other option is limit the size of the array that you want to keep in memory. when it reaches a certain size, you discard the older data.

I don't understand what you are doing with the x-axis multiplier and what you want to do. Since you are getting a waveform data type, it already includes t0 and dt information and you should not be building an array with something else if you want to reflect real-time data. All you have to do is change the formatting of the x-axis to absolute time. If what you really want to do is display more or less than 1 second of data, then turn off autoscaling on the x-axis.

Sorry, I don't have 8.0 so I can't answer your question about annotation.

[me.yet.not.me]

Thanks Dennis, I'll try them out!

[Jonnie_5]

As a random sidenote - you can click on your user name to bring up the profile screen, and then click on "Find all posts by this user" to find older theads.

Or use a User Search to find an author.

So your original post is found at:
http://forums.ni.com/ni/board/message?board.id=170&message.id=183893#M183893