DaqMX & TDMS Logging - No Datestamp and dt until Close

In our application, we are continuously logging data to a TDMS file using the "DaqMX Configure Logging (TDMS).vi". However, there are times when we need to look at the TDMS data while the application is still running (i.e. when a failure is found). What I've noticed is that the initial timestamp and dt are missing from the TDMS file until the "Stop and Clear Tasks.vi" is called, which in our application only occurs when the application is being terminated.
In other words, when I go to look at the TDMS data while the app is running, the TDMS File Viewer shows the time starting in year 1903 and the wrong sample width until after the application exits, and then it shows the correct time and sample time. How can this be fixed so that the initial timestamp appears while the app is running?

Duplicate:
http://forums.ni.com/t5/LabVIEW/DaqMX-Access-TDMS-dt-and-timestamp-Before-quot-Stop-Task-quot-is/m-p...
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I write digital port by 'DAQmx Configure Logging.vi' and receive TDMS file with 8 boolean channels. How can I write to 1 integer channel?

Hello!
I want to write 1 digital port from PXI-6536 with streaming to TDMS file.
I'm writing by 'DAQmx Configure Logging.vi' and become TDMS file with 8 boolean channels.
How can I write to 1integer channel?
Attachments:
1.JPG ‏27 KB

Hey Atrina,
The actual data stored on disk is just the raw data (that is, a byte per sample in your case). It's really just a matter of how that data is being represented in LabVIEW whenever you read back the TDMS file.
I'm not sure if there is a better way to do this, but here is a way to accomplish what you're wanting:
Read back the TDMS file as a digital waveform. Then there's a conversion function in LabVIEW called DWDT Digital to Binary. This function will convert that set of digital channels into the "port format" that you're wanting. I've attached an example of what I mean.
Note: When looking at this VI, there are a few things that the downgrade process did to the VI that I would not recommend for these TDMS files. It added a 1.0 constant on the TDMS Open function, and it set "disable buffering" on the TDMS Open function to false; you can get rid of both of those constants.
Message Edited by AndrewMc on 01-27-2010 11:21 AM
Thanks,
Andy McRorie
NI R&D
Attachments:
digitalconvert.vi ‏13 KB

DAQmx configure logging (TDMS) and counter

Hi,
I'm trying to stream analog data jointly with counter data to one TDMS file with use of DAQmx configure logging vi. This is quite new but powerful function but I can't manage with it successfully. I'm able to acquire analog data only and display no. of counts simultaneously (attached diagram). I have no idea how attach counter data to TDMS stream as separate channel group.
It is important for me to stream data with this VI bacause I'm sampling analog data with 95kHz per channel (PCI-6143 board).
Could you post any ideas how to resolve this problem?
Best regards
Mark
Attachments:
acq_analog_and_contr.PNG ‏44 KB

Eric, hear is short info about DAQmx configure logging http://zone.ni.com/devzone/cda/tut/p/id/9574.
Yes I thought about producer/consumer structure, It is first alternative way.
There is also another very simple way - connecting encoder to analog input and acquire together with analog signals. Of course It will be neccasary to process sigal from encoder after recording. I'm also concerning such solution
Ok I have to sleep with this problem
Best regards
Mark

Data collection was switched from an AI Config task writing to an hsdl file to synchronized DAQmx tasks logging to TDMS files. Why are different readings produced for the same test?

A software application was developed to collect and process readings from capacitance sensors and a tachometer in a running spin rig. The sensors were connected to an Aerogate Model HP-04 H1 Band Preamp connected to an NI PXI-6115. The sensors were read using AI Config and AI Start VIs. The data was saved to a file using hsdlConfig and hsdlFileWriter VIs. In order to add the capability of collecting synchronized data from two Eddy Current Position sensors in addition to the existing sensors, which will be connected to a BNC-2144 connected to an NI PXI-4495, the AI and HSDL VIs were replaced with DAQmx VIs logging to TDMS. When running identical tests, the new file format (TDMS) produces reads that are higher and inconsistent with the readings from the older file format (HSDL).
The main VIs are SpinLab 2.4 and SpinLab 3.8 in folders "SpinLab old format" and "Spinlab 3.8" respectfully. SpinLab 3.8 requires the Sound and Vibration suite to run correctly, but it is used after the part that is causing the problem. The problem is occuring during data collection in the Logger segment of code or during processing in the Reader/Converter segment of code. I could send the readings from the identical tests if they would be helpful, but the data takes up approximately 500 MB.
Attachments:
SpinLab 3.8.zip ‏1509 KB
SpinLab 2.4.zip ‏3753 KB
SpinLab Screenshots.doc ‏795 KB

First of all, how different is the data? You say that the reads are higher and inconsistent. How much higher? Is every point inconsistent, or is it just parts of your file? If it's just in parts of the file, does there seem to be a consistent pattern as to when the data is different?
Secondly, here are a couple things to try:
Currently, you are not calling DAQmx Stop Task outside of the loop; you're just calling DAQmx Clear Task. This means that if there were any errors that occured in the logging thread, you might not be getting them (as DAQmx Clear Task clears outstanding errors within the task). Add a DAQmx Stop Task before DAQmx Clear Task to make sure that you're not missing an error.
Try "Log and Read" mode. "Log and Read" is probably going to be fast enough for your application (as it's pretty fast), so you might just try it and see if you get any different result. All that you would need to do is change the enum to "Log and Read", then add a DAQmx Read in the loop (you can just use Raw format since you don't care about the output). I'd recommend that you read in even multiples of the sector size (normally 512) for optimal performance. For example, your rate is 1MHz, perhaps read in sizes of 122880 samples per channel (something like 1/8 of the buffer size rounded down to the nearest multiple of 4096). Note: This is a troubleshooting step to try and narrow down the problem.
Finally, how confident are you in the results from the previous HSDL test? Which readings make more sense? I look forward to hearing more detail about how the data is inconsistent (all data, how different, any patterns). As well, I'll be looking forward to hearing the result of test #2 above.
Thanks,
Andy McRorie
NI R&D

Our airport extreme network works fine with our 6 devices. But when someone comes over and tries to log on, they can't until we restart the airport. Then they can get on, but it knocks one of our devices off the network. Any ideas?

Our airport extreme network works fine with our 6 devices. But when someone comes over and tries to log on, they can't until we restart the airport. Then they can get on, but it knocks one of our devices off the network. Any ideas?

I have not done a factory reset, I was trying to find out if I had some setting configured wrong first. I figured I'd just make things worse if went through a reset!
Here is a couple of screen shots:

Analog pulse, external trigger and TDMS logging

I am working on a VI that will output an analog pulse, then log data when it receives an external trigger. I have both parts working separately: I can output the pulse and read data when an external trigger is received (Pulse&Acq.jpg), and I can log data when an external trigger is received (TDMS Logging.jpg). However, when I try to combine them I cannot import the resulting TDMS file (Pulse&Log.jpg). I get the following error: USI encountered an exception: (326): Bulk:: GetValues failed for attribute. Additionally, the importer opens two workbooks, which appear to be identical, and both have the USI error.
Any ideas? Thanks!
Attachments:
Pulse&Acq.jpg ‏138 KB
TDMS Logging.jpg ‏39 KB
Pulse&Log.jpg ‏130 KB

Hello,
For the bottom part (Analog Input triggered by digital pulse and saved in TDMS) you start the task AFTER the pulse is sent (by the top part), if you place the start for the analog task before the while loop I think it will work fine.
EDIT : The thing that surprises me a bit is that the Pulse&Acq example works... maybe I'm just all wrong...
Hope this helps
When my feet touch the ground each morning the devil thinks "bloody hell... He's up again!"

DAQmx TDMS streaming

When streaming data to a TDMS file in LabVIEW I have a DAQmx task that uses reference trigger. Is it possible to read the file during the acquisition? It appears that the code is not writing to the disk until the acquisition is complete, by then it's too late for the application I have in mind.
I tried to open the file, set the buffer size (smaller), and close the file, but that resulted in the file not even getting created (no data even after the acquisition had completed).
Any suggestions would be greatly appreciated.
David Dupont

Hi David,
Let's simplify the problem by ignoring TDMS for now. When you do a reference triggered acquisition with DAQmx, when does the data become available to be read from the DAQmx task? The answer to that question depends on the type of device.
I wrote a quick test VI (attached) to demonstrate the difference. It performs a reference triggered AI acquisition, acquiring 5 seconds of pretrigger data and 20 seconds of posttrigger data (at 100 S/s, so 500 pretrigger samples and 2000 posttrigger samples). A counter/timer is used to generate the trigger 7 seconds* after the start of the acquisition. During the acquisition, the "available samples per channel" and "total samples per channel acquired" properties are queried at regular intervals, as well as the "counter output pulse done" property indicating where the trigger was generated.
Here is the behavior of an M Series board: none of the samples are available to read until the entire acquisition is complete.
On M Series, until the acquisition is complete, AvailSampPerChan returns 0. This happens because the beginning of the posttrigger samples is determined by counting 2000 samples back from the last sample, and the beginning of the pretrigger samples is determined by counting 500 samples back from the beginning of the posttrigger samples. (As I mentioned
previously, a workaround is to use the RelativeTo and Offset properties to make the samples available sooner, but then you have a different problem: finding the trigger.)
X Series devices (as well as SC Express and NI 6535/6/7 devices, as far as I know) display a significant improvement: the pretrigger samples are available as soon as the trigger is detected, and the posttrigger samples are available as soon as they are acquired.
On X Series, AvailSampPerChan jumps from 0 to 500 when the trigger is detected, and then it increments continuously. Note that it is still impossible to read any pretrigger samples before the trigger is detected, because doing so would require predicting when the trigger will occur, before it occurs.
When you enable TDMS logging, DAQmx can't write samples to the TDMS file before they are available for reading, so reference triggering still limits when you can read back the data from the TDMS file.
What type of device are you using? Is it a USB device? USB also affects when data is available for reading, because data is transferred in larger chunks to reduce communication overhead.
Brad
* I didn't use a start trigger to synchronize the counter with the AI task, so the 7 second delay is not exact.
Brad Keryan
NI R&D
Attachments:
Ref Trig Data Arrival.vi ‏37 KB

Configure Logging VI start and stop without losing or dropping data

Hi there,
I am currently using a M-series PCI-6280 and a counter card PCI-6601 to do measurements on Labview 2010.
I have 3 tasks set up, 2 linear encoder counter tasks on the 6601 and 1 analog input task with 4 x inputs on my 6280. These are all timed with a counter on the 6601 through an RTSI line.
On all of these tasks, I have a similar set-up as the picture in http://zone.ni.com/devzone/cda/tut/p/id/9574 except they are all set up as "Log" only and "create/replace" file for the configure logging.vi.
Since I want to have the encoders continuously locate my position, I never "stop" the counter tasks. However, I need to use the data acquired after every move along the path to obtain and process the location and the subsequent analog input data points I have. What I have done, is I would "stop.vi" my sample clock on the counter, then open the tdms file, read the tdms file, get the array from there, close the tdms file, then "run.vi" the sample clock on the counter. However, I found when I stop the sample clock, not ALL the data points have been streamed into the file.
For example, say I move my carriage to 100mm to the right while logging, then stop the sample clock, obtain the array from the tdms file, find the size of this array called "X" for future use. Then, I move the carraige back to the origin WITHOUT starting the clock again. THEN I start the sample clock again and move 100mm towards the left. After this is done, I again, stop the sample clock and obtain the data from my tdms file starting the offset of read at "X+1". I EXPECT that this array SHOULD start at 0 then move on to 100mm to the left. However, what it does, is I see the data start at 100mm from the right for a few data points, then JUMPS to 0, then moves to the left as expected.
I propose that this means that when I stop the sample clock, the data from the counters (buffer?) have not all been streamed to the tdms file yet, and when I start the clock again, the remaining gets dumped it. Here, I am confused since I thought that "configure logging.vi" streams directly into the file without a buffer.
I was wondering if I am doing anything wrong, expecting the wrong things, and if there is a way to implement what I want. As in, is there a way to flush the remaning data in the "buffer" (i tried the flush tdms vi, but that didn't work and I didn't think it was relevant) after I stop the clock or something like that, or is my implementation competely off.
Thanks for reading,
Lester
PS. Having a way to read the most recent point from the counters would be awesome too. However, everytime I set the offset/relative to most current, it says that I cant do that while logging, even though I saw a community post saying that it works with analog inputs. Maybe this is off topic, but yeah, currently I'm just trying to get the arrays from tdms working, THANKS!
Solved!
Go to Solution.

Hello, Lester!
There are a few solutions for you here.
First, since you don't need the excess data points, you can set the "DAQmx Read" Property Node to "Overwrite" any data from previous acquisitions.
To do this, first select a "DAQmx Read Property Node" from the functions palette. The first property should default to "RelativeTo." Click on this, and instead select "OverWrite Mode" (see attached). Next, right-click on the input, create constant, and select "Overwrite Unread Samples" from the drop-down enum. After wiring the other inputs and outputs on the node, This should accomplish what you're looking for. If for some reason it doesn't, consider the following options.
Your second option is to limit the buffer size. If you know how long you want to acquire data for, you can use the sampling rate (it looks like 5000Hz, in your case) to determine the number of samples to acquire. Simply use the "DAQmx Buffer Property Node" and input the number of samples desired. When the required number of samples is acquired, the buffer will begin to overwrite the old samples. This, of course, is not a very flexible method, and obviously requires a pre-set number of data points.
Your final option is to do a brute-force open and close of your task with each acquisition. Simply use the "Clear Task" and "Create Task" functions with every new set of data desire. This should clear the buffer, but will be fairly slow (especially if you eventually change your program to take many sets of data very quickly).
As mentioned, the "OverWrite" property in the "DAQmx Read" node should take care of this for you, but feel free to try the other options if they better suit your needs.
Let us know if you have any further questions!
Best,
Will H | Applications Engineer | National Instruments
Will Hilzinger | Switch Product Support Engineer | National Instruments

Daqmx Configure Logging with Time Stamp

Hi All,
I was wondering if it is possible to use Daqmx Configure Logging to log both data, and a row of the exact time (not a relative one), or at least add the FIRST time and date to the information?
Thanks,
Lester

Hi,
I got it to work, I just forgot to put in the "Group Name" and "Channel Name" which is necessary to get the properties, I wasn't aware of that. The info can be seen at http://zone.ni.com/devzone/cda/tut/p/id/3539 .
I got the time stamp now, but the resolution is only to seconds. I tried using the "Format Date/Time String" vi to format the resolution to milliseconds, but that doesn't seem to work because all the decimals after the seconds is just ".000000". Does TDMS always start at .000 seconds, or does it just not go down to that resolution of timing?
Thanks for your help,
Lester

Position, Velocity, Acceleration From Single Encoder, With TDMS Logging

I'm still a fairly new user when it comes to Labview. I started to feel comfortable enough to check out TDMS data logging and I'm kicking myself for not using it earlier.
That said, I am currently reading angular position from an encoder, and estimating it's velocity and acceleration from the sampling rate & encoder resolution. I'm using an FGV to do all the calculations and I've fine-tuned it to be as accurate as I would like.
What I would like to do is implement TDMS logging that records position, calculated velocity and acceleration with the Log and Read option of TDMS. I'd like these to be synchronized with the encoder reads, and I would like them to be handled by a single DAQmx Read vi. As far as I can see though, you can only read the position information from the encoder. I tried to drill down into the DAQmx Read.vi to create a modified version so that I could eploit the TDMS logging, but the subvi uses a call library function vi that currently is beyond my abilities.
I've been in MAX and I can't create any additional outputs for velocity and acceleration. It seems like MAX takes enough information to create approximations from the sampling clock and resolution of the encoder. Why doesn't it (or if it does, how do I implement it).

What hardware are you using for reading the encoder? I have recently completed a similar project where the encoder was connected to a counter that was triggered by the counter increasing, so that it would only read on new positions, this worked reasonably well and seems like it should work well for your case.

Parallel TDMS Logging

Good day all,
Just for a brief summary, I have a PCI-6280 M-series board using LV2010.
Currently, I have 4 Differential AI inputs created on one task, and a Linear Encoding Input using a counter on another task. As you can probably guess, I would like to know the different AI measuremetns at every position I am at (using the linear encoder). Since this is such a big task, I have decided to use the "DAQmx Configure Logging.vi" for logging into a TDMS file.
However, I noticed that both tasks could not be written or "streamed" at the same time. I read on this link that a way to do this is to concactenate the files together. However, I was wondering if this would affect how "synchronized" the position and measurements would be. Is there a better way to do this?
Thanks
Lester
Solved!
Go to Solution.

Hey Lester,
Since all the concatenation is done as post-processing it should not affect the synchronization of your data. Another forum you can check for information is here:http://forums.ni.com/t5/Multifunction-DAQ/Multiple-TDMS-DAQmx-streaming-to-the-same-TDMS-file/td-p/1.... Please let me know if you have any additional questions.
Regards,
Kevin
Product Support Engineer
National Instruments

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DaqMX & TDMS Logging - No Datestamp and dt until Close

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