Be sure to use "One header per segment" option when saving data

[Forrest_Bao]

Hi, I just noticed a trick on using the ECG Feature Extractor of NI Biomedical Starter Kit. When you save the data acquired from your DAQ, either in LVM or TDMS format, be sure to check "One header per segment" in "Write to Measurement File" express VI. Otherwise, ECG Feature Extractor will only load the part of the data specified by the "Samples" tag.

Another solution is to manually change the number of samples by your actual amount of samples in the "Samples" tag if you chose "One header only" when saving the data.

[ZJ.Gu]

Hi Forrest,

Thanks for your trick .

ZJ Gu

[Forrest_Bao]

For those who do not know what I mean by "Samples" tag, I am attaching a snapshot to explain. On Linux or Mac OS X, you can use head command to check the head part of your LVM file. The Samples tag is highlighed. By default, it is the number of samples per segment. But since i chose only one header for all segments when saving it, it was 1000. Now I have changed it to 84000 and ECG Extractor has no problem with it.

Also, for those who have no idea on the number of samples, I am attaching another snapshot to explain.

If you use tail command on Linux or Mac OS X, you can see the ending part of your LVM file. The last line of my file is 83.999000, -0.070161. According the specification in the head, 83,999000 is the last time stamp. So the number of samples is [(last time stamp) - (X0) ] / Delta_X where X0 and Delta_X are specified in the header as shown in the snapshot above.

For more details about LVM format, please refer to the specification: http://zone.ni.com/devzone/cda/tut/p/id/4139