I am recording low-bandwidth data in a stripchart-like fashion. I would like to add notations to the data that are time-synchronized and logged with the data, just like I was physically writing notes on a paper stripchart. Is this possible in SignalExpress? If not in SignalExpress, could someone give pointers to doing this in LabView?
Do you need to annotate your log while recording is in progress (for example, by pressing per-defined keyboard keys during logging), or do you just need to annotate the log from the data viewer after logging has completed?
None of these operations are currently possible in SignalExpress, but we are interested in what your needs are to improve the next version of the product.
I suppose either solution would be suitable. Ideally, the annotations could be made in realtime as the data is coming in. However, being able to add them after the fact would be a usable work-around. Currently, I just use Notepad: I type in the time (HH:MM:SS), tab over, then write the comment as the data comes in. The notepad text file travels with the recorded data file, and is used as a reference when reviewing the data. Sometimes, I have exported the SignalExpress time history data to Excel, then transcribed the comments to that Excel worksheet.
You can do this in LabVIEW in a number of ways. The easiest is probably to have a text field on your front panel, and every time you change the text, you write the data to your file with the current system time. Use the event structure to trigger the write to the file. To coordinate with your data file writes, you probably want to use a single, non-reentrant VI for both data and notation writes. That way they will be automatically interleaved. The VI would take either data or text as an input, with a switch to determine what gets written. Open the file once at the beginning of your data acquisition and use the file reference as an input to your write VI.
Note that detecting when a text field changes is somewhat tricky. By default, LabVIEW signals a change in a text control when the control loses focus (you click off the text box or click the enter button on the toolbar). You can set options to make the text control send change events on every key stroke or when the enter key is pressed. You probably want to set the latter.
Let us know if you need more info.
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