I am trying to save TDMS files that ideally contain the following:
- 3 xy graphs (each containing two 1d arrays)
- 1 waveform
The problem i'm running into is that when I convert the xy graphs to waveforms, the x-axis is converted to time, which isn't real or useful to me. I've attached screenshots of what the XY graph should look like VS what it ends up looking like with the waveform.
How to I make sure the x-axis is preserved so that I can save to TDMS?
Edit: VI is included & pictures have been updated to better represent my code.
TDMS Waveform Example.vi
I am supporting a legacy application in LV2010, running on a realtime PXI controller. The application is throwing occasional TDMS errors, typically -2505, when I do TDMS Flush or TDMS Close operations. The description of this error is simply "LabVIEW failed to write data to the TDMS file," which doesn't really tell me what happened. Every time I write or flush, the same quantity of data is being written, and most of the time, it operates as expected. After iterating for anywhere between 2 and 14 hours, though, it eventually throws the error.
Does anyone know in more detail what this error means, and how to deal with it?
By Christian Butcher
Question: I'm trying to determine the 'best' way to structure my data when storing to disk. My data comes from a variety of different sensor types and with quite different rates - e.g. temperature data (currently) as a 1D array of temperatures and a timestamp [time, t1, t2, ..., tn] at maybe 1 Hz and analog waveform data from load cells at data rates ~O(kHz).
I also want to be able to read back data from previous experiments and replot on a similar graph.
Reading threads on this forum and at NI I'm uncertain if I'll be better pursuing a set of TDMS files, probably one per sensor type stored at the group/channel level, then at the end of an experiment, collating the TDMS files into one master file and defragmenting, or trying instead to write to a SQLite database. (I have nearly no experience using SQL, but no problem learning - drjdpowell's youtube video was already very informative.) An alternative possibility mentioned in a thread somewhere here was to write TDMS files, then store records on which files hold what data in what I understood to be a catalogue-style SQL database.
Could anyone with a clearer idea/head than me comment on which avenues are dark tracks down which time will be easily lost in failed attempts, and which seem likely to be worth trying?
Background: I'm currently rewriting some code I wrote last year based on the 'Continuous Measurement and Logging' template/project. The logging in that case was writing to a single, binary file. Keeping my data format in line as I changed sensor arrangement became increasingly annoying and an ever expanding series of block diagrams lead me to start on the 'Actor Framework' architecture.
I have some initial progress with setting up actors and generating some simulated data, passing it around and getting it from different formats onto a waveform or XY-graph (can be chosen by choice of child class to insert into a subpanel). I'm now looking to write the logging code such that I have basic implementations of several of the components before I try and write out all of the measurement components and so on - I already have a temperature measurement library for an LTC2983 based PCB and so can use that to test (with hardware) inputting 1D arrays, whilst I'm planning to use just the sine wave VIs to test waveform input.
I'm not so far into this set of coding that anything is set in stone yet, and so I want to at least try and start off in the right direction. Whilst it seems likely changes to requirements or plans will require modifications to whatever I write, it would be nice if those weren't of the same magnitude as the entire (e.g. logging) codebase.
Apologies for the somewhat verbose post.
I'm using the 9229 and borrowed a community example to log 4 voltage inputs to TDMS. I need to output RMS voltage on channels 1&2 and the wavform on channels 3&4.
Essentially what I've done is averaged channels 3&4 using the same # of samples that the RMS is averaged, that way I'm able to make sure they are time synchronized (see code attached). Another advantage doing averaging the samples is that I am reducing the amount of data to analyze later.
When i compare the TDMS read results to the # of samples in the TDMS file there seems to be a discrepancy in time. I tried to add a time stamp to the logged TDMS file but couldn't get it to work. besides using time stamps, Is there an easy way to confirm that I am saving all of the data I am capturing? Eventually i will be logging data at 30min-40min intervals so I want to make sure that i'm not losing data.
I'm currently investigating using TDMS as a data storage for a new measurement method. In our routine, we sweep up to 3 outputs (with X, Y and Z points each) and record up to 24 channels so we have XxYxZx24 datapoints.
We create the following:
Up to X data points for 24 channels of data interleaved in the first dimension (multichannel 1D)
Up to Y times this first dimension (making the data multichannel 2D)
Up to Z times this second dimension (making the data multichannel 3D)
So in a sense, we create 4D data.
Trying to use our old method of storing the data in memory fails quickly when the number of steps in each dimension increases. So we want to store them in TDMS files. But looking at the files and trying to imagine what read speed will be like, I'm unsure how to best store this data. DO I need multiple TDMS files? A single file? How to map the channels / dimensions to theinternal TDMS structure?
In a further step to my efforts, I would be investigating having the routine for retrieving any sub-set of this data (1D or 2D slices from any combination of dimensions but almost always one channel at a time.
Can anyone with more experience with TDMS files give some input and help a TDMS noob out?