TDMS: Best way to store small integers with scaling?

[JKSH]

I'd like to log high-speed data in a TDMS file. The data arrives as I16 (non-DAQmx), with some scaling + offset.

If I call "TDMS Set Scaling Information" and then write I16 arrays to the TDMS file, they all get converted to DBL behind the scenes (NI_DataType == 10). This seems a bit wasteful and causes file bloat.

Is there a way to store scaling information without triggering an implicit conversion to DBL? Or would I have to scale all the data myself and then write smaller types (say, I32 or SGL) into the TDMS file without writing the scaling info?

[GerdW]

Hi JKHS,

TDMS allows to set properties for each channel/group in the TDMS file.

So you can easily save your data as I16 (as is) and store the scaliing information as property of the channel…

[JKSH]

---

@GerdW wrote:

TDMS allows to set properties for each channel/group in the TDMS file.

So you can easily save your data as I16 (as is) and store the scaliing information as property of the channel…

---

Thanks GerdW.

To confirm that I've understood your suggestion correctly: I would avoid "TDMS Set Scaling Information" but instead write the scaling info as a custom property. The reader of the TDMS file would then read the raw I16 values back out, get the scale/offset property values, and then perform the scaling themselves as a post-processing step; is that right?

I was hoping that there's a way to store the data points as I16, store the scaling info, and then have "TDMS Read" (or an off-the-shelf TDMS viewer) do the conversion automatically. Does such a feature currently exist?

[GerdW]

Hi jkhs,

---

@JKSH wrote:

I was hoping that there's a way to store the data points as I16, store the scaling info, and then have "TDMS Read" (or an off-the-shelf TDMS viewer) do the conversion automatically. Does such a feature currently exist?

---

AFAIK there is no such feature built in. You either get scaled data stored as DBL, or you get unscaled data stored as I16.

When you need a feature not provided by NI then you need to implement it on your own...