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TDMS minimum property

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What forces TDMS Minimum and Maximum properties to be calculated?

I generate a TDMS file, open it with TDMS viewer or Excel toolkit, the Minimum and Maximum Values are empty.

If I convert it to TDM file and open, the values are calculated.

If I attempt to "Set" the Values, I get Error -2526 "Cannot write to this value"

Where may I find a list of NI TDMS properties?

Thank you, Jeff

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Message 1 of 8
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There is a few really good white papers on this.  I just can't seem to find them right now.

 

It sticks in my head though that the Max, Min, and monotonicity are calculated during indexing.  Or was it when DIAdem read the file?  I have the articles printed up at my office.  I'll have to see if I can find them again.


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Message 2 of 8
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The TDMS File contains groups and chanels of data

 

The File, Groups and Chanels may each have properties .  These are almost limitless since they are "Name-Value" pairs.

 

Some Common user properties are "Minimum" and "Maximum"  In fact they are so useful and common that some viewers automatically assume you will want them for any chanels that contain numeric data and calculate them by default.  BUT, unless you have calculated them and written the values to the file they do not exist in the file. (Although- thay are fairly easy to calculate)

 

Now, even some of those data writers think those properties are fairly important.  If you look under the advanced section of the "Write to measurements file" Express vi configuration wizard.  a lot of the common properties may be selected for "automagicilly" being added to the TDMS file

Capture.PNG

This is probably what you are used to seeing happen in someone else's existing code.

"Should be" isn't "Is" -Jay
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@JÞB wrote:

 

Now, even some of those data writers think those properties are fairly important.  If you look under the advanced section of the "Write to measurements file" Express vi configuration wizard.  a lot of the common properties may be selected for "automagicilly" being added to the TDMS file

 

This is probably what you are used to seeing happen in someone else's existing code.


I don't believe the question is about manually writing properites.  I believe the question was when are the properties written, that the TDMS Write function creates on its own.  Things like Datatype, Unit, Length, Minimum, Maximum, Description, NI_ArrayColumn are a few that get written to a channel within a group without having to do any other work.  I assumed this was written when ever the TDMS file is flushed to disk but I could be wrong.

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Message 4 of 8
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The Minimum and Maximum properties are not pre-defined properties in LabVIEW/TDMS (Please refer to http://zone.ni.com/reference/en-XX/help/371361K-01/glang/tdms_set_properties/ for all the pre-defined properties). Thus, they are added by third-party software/components like DIAdem and you should properly turn to them for the detailed information.

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Yes, I was asking what triggers the calculation of certain properties (Minimum, Maximum).

Based on the responses, I am calculating those values and setting them explicitly.

Thank you for the reference links for the TDMS Properties. 

-jeff

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Message 6 of 8
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Measurement studio now has .NET TDMS libraries and example code.   As far as I can see the maximum and minimum value are handled by the library automatically - I see no code that performs this calculation.

 

How can I be certain that the maximum and minimum is over ALL the data and not just what the tool read in.   We have a 3.5 GB TDMS file and the max and min values are highly important.  We've noticed that it doesn't display all the data which is reasonable give it would take about 3.5 million rows per channel.

 

The length (# of samples) is definitely correct.

 

We have 128 channels with approximately 3.5 million samples per channel (collected over about a month). 

 

We used signal express to pair a PXI-4071 DMM with a PXI-2530b Switch Matrix (bi directional triggering).  We used all 128 channels at 5 1/2 digits measuring a DC voltage.

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Message 7 of 8
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It looks like this thread is solved. I think it will be a good idea if you could start a new thread with your question. You will get better response this way

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