How can I add the timestamp to data captured using Write Labview Measurement Vi?

[brinda]

I am capturing multiple analog differential inputs - I want to timestamp these samples and store this into a simple spreadsheet format ( supported by the write labview measurement vi). It would be great if someone could tell me how to go about doing this.
Thanks
Brinda

[BJD1613]

What you can do is to use the following example and using the concatenate strings function you can add it to each of your samples. Using a tab constant between them will tab delimit the time and sample. Using an end of line constant will allow a new line to start after you timestamp and sample. You also can use the write characters to file function or the LV measurement file. Hope this helps.

[BJD1613]

sorry here is the attachment. No coffee yet 🙂

[brinda]

Hey

Thanks !! Just any idea how accurate the timestamps are with respect to the sampling event ?

Brinda

[Philip_Courtois]

Hi Brinda,

The timing functions in LabVIEW can present absolute system time with a resolution of one millisecond (Get Date/Time In Seconds), but this timing is dependant of the software timer of your operating system. Are you interested in the relative time between measurements on the hardware or are you looking for the absolute system that the data was acquired (less relatively precise)?

Best regards,
Philip C.
Applications Engineer
National Instruments
www.ni.com/ask

[brinda]

Hi Philip

I am looking for absolute system time regarding when the data was acquired.

Brinda

[Philip_Courtois]

Hi Brinda,

To get the absolute time from your measurements when the data was collected, use the Waveform data type for the output of �DAQmx Read.vi� (for DAQmx) or �AI Read.vi� (for Traditional DAQ). The Waveform includes the t0 which is the start time of the acquired data.

Notice that this time is relatively precise, but only relates to the computers clock to get the absolutism.


I hope this answered your question.

Best regards,
Philip C.
Applications Engineer
National Instruments
www.ni.com/ask