Order Analysis Toolkit: Even angle reference signal processing

[MiamiVipul]

Hi:

Q1: Labview: Memory Full message.

I was using Order analysis toolkit and some of its examples. When I executed the "Even angle reference signal processing.VI", I'm receiving memory full  message. Can anybody who is aware of this toolbox give me a suggestion?

My system has NI 4472 card, and I'm collectig signals from 2 displacement sensors, and an analog Tacho.

Q2: How to save Cluster Data to a file:

I was trying to direct the data going to to graph "Compensated Even Angle Signal" to a data file. Basically, I wanted to see the Time vs Amplitude data on a text file in addition to the graph (Compensated Even Angle Signal). How do I convert the data type "1D Array of Cluster of 3 Elements" into a simple data file that list time vs amplitude??

Thanks a lot.

Vipul.

[Neil_S.]

Vipul,

Thanks for posting to the NI forums. 

Q1:
I was not able to reproduce the issue of an out of memory error.  I am successfully able to run the example without the error.  Could you provide me more information about how it is happening?  What tab do you have selected when the error occurs?  Are you able to successfully acquire anything before the error occurs?  What version of LabVIEW and the toolkit are you using?  What settings have you tried for the VI?

Q2:
The easiest way to save this information to a text file is to use the write to spreadsheet file VI.  You can take a look at the example below.  You have to generate a time array because the cluster does not contain an entire time array it only contains a start time and the dt or the time between points.  I used this information to generate an time array.  Also there can be more than one signal displayed.  I iterated between signals to add each signal to the file.  You will need to modify the example to suit your needs but hopefully it gets you started.

Example:

Regards,
Neil S.
Applications Engineer
National Instruments

Message Edited by Neil S. on 08-28-2006 01:27 PM

[MiamiVipul]

Thanks a lot for the reply. I will try your code (for Q2) and let you know the progress.

Again, for Q1:

I'm using Labview 7.1 and OAT 2.1 on XP platform, with 1GB RAM, AMD 1.8 GZ processor.

I was able to collect waveform in "Extract even Angle Reference" tab withour any trouble. I collect 1000 data points at a rate of 1800 samples/sec. Then I change the speed and as soon as I select "Remove slow-roll error" tab, it will wait few rotations and gives me the "Memory Full" error.

Even in the "Extract even Angle Reference" tab, I do not see any pattern on the graph for "Even Angle Reference".

Wne I have motor turning and the encoder signal is read through CH 6 (One pulse/rev) and if I start collecting data, it gives this error message.

(But when I stop the motor, but keep the sensor power supply on, I get noise through my displacement sensor channels and also via my analog tacho channel. It works without any trouble for this noise signal !!)

Any help would be greatly appreciated.

[Neil_S.]

Vipul,

With your additional information I was able to reproduce the out of memory error here.  I have escalated the issue to R&D and will work with them to see if we can find a possible workaround.  If you run across any additional information you think will be helpful in finding a workaround let me know.  I was able to discover that this issue only seems to occur when you change the number of samples from the default value.  I got the issue to occur even when I never went to the Extract Even Angle Reference tab and only acquired from 2 channels.

I am not sure if I understand what is going on as far as the graphs are concerned.  Is it that you are not getting anything on the graph at all or does the information just not seem to have a pattern?  You also mentioned you were getting an error when the motor is turning and you are reading the encoder through channel 6.  Is this the memory is full error or some other error?

Regards,

Neil S.
Applications Engineer
National Instruments

[MiamiVipul]

Dear Neil S.

Thanks a lot for your comments and also submitting it to your R&D.

I can collect a data sample at slow-run, and then when I speed-up the motor, I can proceed with een-angle compensation, etc. for a very short time. As soon as it starts displaying things on the graphs, it will give me this memory error.

I need one more favor from you. Last time you posted an image for modifying my VI to write data to a file. I tried to incorporate it into my VI but I'm having hard time getting it to run, as I'm new to Labview. Would you mind posting it as a VI? It would be great if you can take my VI and modify it; but if it is too much work, please kindly post your portion as a Labview VI (in version 7.1).

Again, thanks a lot.

Vipul.

[Neil_S.]

Vipul,

Attached is a VI in LabVIEW 7.1.  Let me know if you have any questions about it.  As far as the other issue is concerned, does changing the acquisition rate improve anything?  I noticed this error occurs often when each iteration of the loop can only detect a few tach pulses.  Is it possible the VI is missing pulses when you speed up the motor?  I would try to adjust the samples per channel and acquisition rates to see if you can avoid the error.  Since I don't have your exact setup it will be difficult for me to figure out what settings might reduce the chances of memory errors.

As far as the memory error goes in general: This was reported to R&D (40TC17VF) for further investigation.  The number is an internal number used to track the issue.

Let me know if you have any further questions.

Regards,

Neil S.

Message Edited by Neil S. on 09-01-2006 10:35 AM

[MiamiVipul]

Neil S.:

Thanks for the VI.

Well, I will give you more information about my system. I have NI 4472 card and Labview 7.1, OAT 2.1 on XP operating system with 1GB system memory. This is the only card I have in my system.

I'm collecting two displacement signals, 90 degree apart, mounted perpendicular to a rotating shaft. I also have an optical encoder givins a pulse per revolution. So I'm using OAT Even Angle Reference Signal Processing (analog tacho) VI to collect and visualize my data. Since very minimal giudelines are available on this tool kit, I'm basically running things by trial-and-error basis.

I collect 1000 samples per channel at 1800 samples/sec. At slow-run, I have the shaft running at 120 RPM. In other wards, I get a pulse from tacho at 0.5 sec. apart, and I'm collecting data for about 0.56 sec. so that I do not skip any of the pulses.

At slow-running, at Extract even angle ref. tab, I collect one sample, and I immediately see the collected waveform on "Acquired Waveform" graph. I do not see anything on the "Evan Angle Reference" graph.

Once I increase the speed, I click on the "Remove slow-roll error" tab, I see few pulses on the "Acquired Even Angle Signal" graph, and may be few pulses on the "Compensated Even Angle Signal" graph. Also, it will immediately tell me that "Memory Full" and stop the execution of the VI.

FEW OBSERVATIONS:

When I runn the setup at very slow speed, I get this memory full almost immediately. If I run the shaft at a much higher speed, I can see the graphs for a while. If the speed is even increased, it will show the graphs for a longer time without memory error.

Once I switch-off the power to disp. sensors and encoder, I basically get line noice. This noice signal work perfectly with the VI ???? Every graph is functioning very well !

Well, I do not really know what's going on. Any help to solve this OAT problem is highly appreciated. Attached are few JPG's when I have only the noise.

Thanks.

Vipul.

[Jeff_T.]

Vipul,

I have been working with Neil on this issue and wanted to let you know that we have discovered what we believe is a bug in this example.  We have seen that the "Memory Full" error will occur regardless of system specs and have identified the root cause of the error.  We have informed the developers of the problem and will let you know them moment when we find a work around.  Thank you for working with us on this issue and we will keep you posted.

Best Regards,

Jeff Tipps
Applications Engineer
National Instruments

[MiamiVipul]

Jeff & Neil:

Thanks a lot fpr your prompt attention.

Vipul.

[dmertz]

1.  I am getting the same "Memory is Full" error messages.  Is there an updated "Even angle reference (Analog Tacho)" example VI that corrects this issue?  I have Labview 8.0 with OAT toolkit version 2.1. 

2.  Does my even angle reference sampling rate have to be the same as my acquired even angle sampling rate?

Thanks.