Timestamp edge count

[jball]

Hi.  I am very, very new to Labview.  In fact, I am working on my first program so my question is probably really simple, and I bet I overlooked the question when reviewing previous posts.  Here it goes.  I am using LabVIEW 8.2 and I have some tipping buckets which collect data through an analog edge count.  I would like to timestamp and record the data only as it occurs.  I have figured out how to continuosly save the data without a timestamp, but this is problematic because this will create an extremely large file due to the time requirments.  I will post a screen shot of my code.  Thanks!

[jball]

Bump!

[RavensFan]

You will need to be a little more clear about "I would like to timestamp and record the data only as it occurs.".  What do you mean by "as the data occurs"?

It sounds like you need to do some analysis on the data that you acquire and when it meets whatever is the condition you are talking about, then write to a file.  In that case, the write to a file would be in a case structure.

I would recommend looking at the online LabVIEW tutorials.

LabVIEW Introduction Course - Three Hours

LabVIEW Introduction Course - Six Hours

[jball]

Okay, may be I was not clear enough.  As the data occurs, means that it may be days or weeks inbetween data points and I don't want to continuously save the data for that long.  The DAQ sends a signal everytime a specific volume is obtained.  No data is collected until that volume is reached.  I wish to only write to the file with a timestamp when the specific volume occurs.  I will look over the links, however.

[stanthetiger]

Hi jball,

The size of the measurement file will depend on the sampling rate and the duration of your data acquisition. If you set up your analog trigger correctly, then you shouldn't be logging/acquiring any data until the trigger occurs. If you want to selective log the data depending on certain conditions then perhaps you can place a case structure around the Write to Measurment File express VI.

To log the timestamp to the measurement file, you just need to double click on the Write to Measurement File express VI and change Emtpy Time Column to One Column Only in X Value Column section.

Regards,
Stanley Hu
National Instruments
Applications Engineering
http://www.ni.com/support

[JoeFriedchicken]

Hi,

I'd like you to also expand on how you're collecting your data. What do you mean by "analog edge count"? I don't know what kind of signal you're measuring. Is it an analog signal, and if so, what are these 'edges'? Most of the time, counting edges means counting digital edges, so 0 to 5V rising edges or 5 to 0V falling edges.

At any rate, I'd like to explain a little bit about how a DAQmx task works, and I'm assuming you're continuously measuring analog signals with an analog input task. When you start an acquisition, the board will use the sample rate you specify to grab samples from the analog inputs. If you specify a continuous acquisition, it will continue to grab samples until you end the operation. Regardless of whether or not the signal value changes, the board will grab samples at the same rate. If you only care about when the signal's value changes, then you'll need to read your data and only record it to file when it does change. In that case, Ravens Fan is correct, and you'll need to do some simple post-processing to save the data of interest to you.

[jball]

Thanks!  I didn't get a chance to work on my code any the past few days, but I will take your advice. o_0