Strip Chart history buffer

Hallo,
I have a little crazy question - is there some possibility to access strip chart history buffer?
I'm just lazy to develop data circular buffer management ....
Thanks a lot for any hint!
George

Hi, Evan,
thanks for reply.
My idea is use already used memory of the strip chart (not duplicate the amount of allocating memory) - mainly to export recorded traces - e.g. when user decided: "this is interesting - let's make some analysis of this, maybe at home".
The Strip Chart hasn't simple solution to use cursors - and by exporting the history buffer (traces) to some file / array is quite easy use standard graph with cursors etc.
Of course, the cicular buffer is OK.
George

Similar Messages

How to extract data from Chart History?

Dear all, I have read a lot of posts, but still don't understand how to extract data from Chart history.
Suppose you acquired 1024 points of data every time, then use "build array" to build an array, then send to intensity chart to show, then save the history into a .txt file, but how to extact data from the file?
How Labview store the data in the 2D history buffer?
Anybody has any examples?

The simplest would be to save the 2D array as a spreadsheet file, the read it back the same way.
Maybe the attached simple example can give you some ideas (LabVIEW 7.1). Just run it. At any time, press "write to file". At any later time, you can read the save data into the second history chart.
If you are worried about performance, it might be better to use binary files, but it will be a little more complicated. See how far you get.
LabVIEW Champion . Do more with less code and in less time .
Attachments:
IntensityChartHistorySave.vi ‏79 KB

Programmatically changing chart history length

I'm creating a VI where the user can choose the data sample rate via the wait(ms) used in a while loop. However changing the sample rate effects the time length being displayed on the chart. This is dependent on the chart history length, originally I thought I could just change this programmatically, but the history length doesn't appear on the property node.
I've had a look at the advice in the ni support section:
http://digital.ni.com/public.nsf/allkb/E9784F413A2269E086256F3A0064C8BB
This method seems a bit messy (especially when I'll be doing this for a number of charts), although I couldn't open the example as its v7.1 and I have v7.0.
Is there anything I can do?
Help would be appreciated (deadlines approaching)

The entire point of using a chart is that you update only the last value, so there is no point in writing the history data every loop. For that you can use a graph, which will allow you to do this without using a property node.
The history length is not supposed to control how much data is currently displayed on the screen, but how many points are kept in the buffer, so you can scroll back and see them. When you change the length of the history data array, the chart doesn't seem to like it. It starts acting a bit crazy. Also, keep in mind that there is no point in displaying 1000 points if your chart is 600 pixels wide.
There are problems with what you want to do, like if you add points, where do the extra points come from, or since a chart uses a constant multiplier, what happens to the old data when you change it and so on.
I've modified your example slightly, so that it doesn't write to the property every time and so it handles the enlarging the history buffer case, but it's still buggy and needs more work.
The main problem is that the History property doesn't change the chart length. If I understood you correctly, and you want to constantly display the last X seconds, I still think your only viable option is using a graph. The transition should be fairly simple and if you use a shift register it can handle it.
Try to take over the world!
Attachments:
chart.vi ‏63 KB

How do I programmatically set chart history length?

How do I programmatically set chart history length?

Hi, u could try instead of using a chart, u could use an xy graph with a chart buffer and with the chart buffer defining the length/amount points needed. And this also mimics what happens in a chart.
Stuart
Attachments:
XY_Chart_Buffer.vi ‏54 KB

Chart History Length

Is there a way to programmatically change the Chart History Length of a Chart Graph Indicator?

Hi Dude,
no.
Option:
Use graphs and maintain your own buffer...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

How do I mark a "not measurable" event on a chart history?

I have an application which is working very well and takes measurements - continuously plotting a result on a chart. The chart history is typically a 100 or so measurements. I plot on the chart both an upper and lower tolerance limit, hence the measurment plot should hopefully stay between the two (straight lines) limits.
Occasionally a sample is "missing" and when this happens a "measurement" of zero is given. This is currently displayed on the chart as a sudden drop to zero. The users like this as it shows them clearly that the sample was missing. All OK so far, however...
On rare occasions a sample is present and is measured but for reasons I will not go into we know (and the software can determine) that the measurement result is actually invalid. This situation I call "not measurable" in that although a sample is present it actually cannot be properly measured. The question is this; how do I show this on my chart history?The chart history plot is by far the most looked at display of data for the users. I realise that I could show a message box saying "not measurable" (and intend to do so) but this would only last for that measurement cycle. How do I "mark" the chart to show that there was a sample but that it was not measurable.
I don't particularly want to use a zero value because that is being used quite nicely for the "no sample" situation. Also I don't want to simply not plot anything because the fact that the sample was "not measurable" is potentially very important indeed. Ideally what I would like is to put a marker, say a thick vertical line at the position where the invalid measurment is, in order to both block it out to show that it is wrong and also show there actually was a sample there in the first place.
Any ideas as to how I can do this? Sorry this is a bit wordy!
Regards
Kevin

Hi
I have come up with a quick fix for using a chart which might give you a few ideas. This is just a quick fix and isn’t very nice at all. The green dots are meant to represent the immeasurable data, I have just triggered them by a set of limits. You would be better of using an XY plot and an array which you constantly up date. Using an XY graph will give you a lot more options such as using cursors to mark certain points.
I have attached my quick fix and an example of using text on an XY graph
Hope this at least gives you some ideas
Tim
AE NI UK and Ireland
Attachments:
quick fix.vi ‏17 KB
Text_by_Points_on_XY_Graph[1].vi ‏32 KB

Why do i get crashes when setting chart history length

I am trying to figure out how to get my chart to eat up less memory. At the moment it is capturing from 4 channels at 44100 samples/sec. It is a continuous capture and after a few minutes, the computer just runs out of memory and can no longer keep up with the capture, at which point the Vi quits. Opening up task manager, I noticed that as I capture, the memory gets chewed up really quickly, but when I stop my VI the used memory is not reclaimed. Even if I set the chart history to an empty array when the VI stops. I tried setting the chart history to a smaller number but whenever I set it below 512 the whole computer crashes.

I have seen similar problems. I created a simple VI to test this and am continously getting LabView crashes when I try and write an intensity chart history to an array.
First frame of the vi sequence generates a 100 random number array for the intensity chart display. The next frame in the sequence has the property node for chart history (of the intensity chart)set to read mode and it is wired to a two deminsional array.
So, I generate psuedo chart data and then try to recover the history into an array. It crashes every time. No matter where I set the chart history length. I attempted to do as you had previously suggested and store the data to a file. Same response.... Crashes LabView. Local and online help have not been very hel
pful. Will search the hardcopy literature now.
thanx
WLS
Attached VI
Attachments:
history_grabber.vi ‏22 KB

Cursors for strip chart controls?

I’m using a strip chart control to plot data during real-time. I allow the operator to pause the chart to view old data. The operators would like to be able to see a specific value when the chart is paused, either by enabling cursors, or clicking over a point on the chart with the mouse. I don’t see any way to do this for a strip chart control, or am I missing something?
Thanks!
Angie
Edited to add: I'm using CVI 2010.

Some ideas have been suggested here and here, may be it's of interest

Stack strip chart x axis

Hi y'all
is there a way, besides just putting one strip chart on top of another strip chart and have it aligned just right to hide the x axis and be on the same x scale as the others. For example: Schart #1 represents the pressure in the system, Schart #2 current , Schart #3 voltage.
Now I could have all these on one strip chart but while acquiring data it is hard to determine one line from another when you have 16 channels scrolling past on the same strip chart.
What I am looking for is something like the digital graphs where you have multiple views on the same x axis.
Is there a way to do this besides stacking strip charts on top of one another?
Are there any proposed changes coming that would include this?
Thanks

As far as I know there is no possiblity to obtain your goal other than stacking more charts one on top of each other. The digital graph is lot more simple as digital signals can have only 0 or 1 value, so it is possible to plot them on the same graph with some y-offset without losing the real meaning of the signal itself. With analog signals this is considerably more complex, as each of them must reference to an analog scale.
Alternative ways to address your situation are to use the secondary Y-axis to hold some of the plots or to use the legend to permit hiding/showing individual plots to make easy to the user to read the chart.
Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

Chart history explanation?

Greetings,
Perhaps I am thinking too much on this, or perhaps too little, but I am trying to figure out what chart history length is actually doing.
For example. I'm developing an app right now where I am monitoring 32 channels on a system at 10 Hz. I'm charting up to 10 of any of these channels (user selectable) at any time. This system can expect to be run for several hours for a test and I have been doing long runs to test stability. I've tweaked the time axis on the chart to be hours wide, 10 minutes wide, etc.
So, when I have my chart displaying 2 hours worth of 7 channel data on the screen, I'm getting lost as to what factor a chart history length of 1024 means to me? I'm able to have several hours of data plotted though a history length of 1024 implies I should only be able to see only 1.71 minutes. Can I only recall the last 1.71 minutes of data out of the chart?
Someone shine the light in the darkness for me eh?
Cheers,
Greg Cole
“It is not the ship so much as the skillful sailing that ensures the prosperous voyage.”

Hola,
You are correct, I am using waveform data. I'm attaching a screenshot. Apologies for the undocumented VI's. One sets up the daq task, the 2nd adds a channel to the front which is the sum of three other channels, and the last extracts the channels the user has selected to plot. I have about 2 1/2 hrs up on the chart right now. (started a log after my first post)
um... crap. I must make a correction. My history length is actually 180000 (I forgot I had been experimenting on it yesterday). Man, I'm glad it's Friday. However, I still do not understand the math.
180000 / (5 waveforms @ 10 Hz) = 180000/50 pts. = 3600 second chart length, = 1 hr. Yet I'm at 2.5 hrs.
Apologies for the bad data on the first post.
Cheers,
Greg Cole
“It is not the ship so much as the skillful sailing that ensures the prosperous voyage.”
Attachments:
daqloop.jpg ‏53 KB

How to set legend of strip chart in CVI8.0

Do somebody know how to set legend of strip chart in CVI8.0? I know that in CVI8.5 SettraceAttributeEx() can used to set legend of strip chart, but in CVI8.0, there is no the function. Thank you very much.

Hi Ravi,
If I am not wrong You are referring to article <b>Queues for Prioritized Message</b>. But this is about how to Prioritize message inside XI.
What I am intresetd in is to set a message priority (for example "2")for the message going to MQ. That is when the message reached the detination queue the priority of this message should be 2 in the queue.
Thanks
Abinash

Strip chart time stamp x-axis

Hello,
I have a strip chart and want to set the x-axis to current time from system.
How to do it please?
Thanks

Give this a shot:
http://digital.ni.com/public.nsf/allkb/6F0054EEABAFE4B886256F2700012142
Mark P.
Applications Engineer
National Instruments
www.ni.com/support

Generate report (just data out) from strip chart (DEADLINE LOOMING!!)

I have a VI that contains a dual strip chart ( Scalar data / Double precision floating point numbers) running in a while loop. One of the strips contains pressure information, the other contains deflection information. I need to know how to gather that data as it is recorded, save it to some kind of container during testing, and then output it in a format that I can see columns on Wordpad. Still waiting for MSOffice on my machine. I have tried several approaches, all of which ended in generating only the last 2 values measured. THis is a VI I just threw together yesterday, and it will be relaced by a (nearly completed) state machine next week. I just need something to hold me over until then... I have very little time left before my boss, who thinks LabVIEW is "Black Magic" comes back here to see my test run!!
One should welcome adversity as an opportunity to excel.

Thanks LVGWB!!! You are a guru. I used the example to which you pointed. It worked great. I think I will still have my job. Being a newbie it is kind of overwhelming all of the "apparent" choices available. I appreciate you steering me to a good one. Chris
One should welcome adversity as an opportunity to excel.

Question about strip charts

My question is quite simple:
I have a sequence, with let say 2 frames, in each one of them, there is a loop in which data flows. I have created a strip chart which plot the data from the first loop.
What I want:
I would like to keep the same chart so that when the loop in 1 is over, it starts plotting the data from the second loop.
Thank you,
Noel
and in similarly, I would like to know how to use one numeric input and use it in 2 different loops without having to make the wire go all around the VI.
Message Edited by Akatsuki on 11-28-2005 05:35 PM

Sorry,
herez the VI ;-)
Attachments:
2loop _chart.vi ‏27 KB

Command line history buffer in sqlplus

hi,
this question is not XE specific, but I want to know, whether there is a command line history buffer in sqlplus. It is not very comfortable to to work with sqlplus, when you have to work on a text only vt100 terminal :(

no, not natively but it on linux you can use something like rlwrap which will do it for you

Strip Chart history buffer

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