Problem with measuring with niscope

[christian1996]

Hi,

I have a Question with the niscope measurement. I want to measure a long time period, therefore I am using the Fetch Record. This Vi is running without any problems but at the analysis of the TDMS there is a loose of information. Is there any better solution to save my measurement?

Kind Regards

Christian

[mj0541]

The consumer loop will end when the TDMS Write VI throws an error. You close the TDMS file when the producer loop exits so you would lose whatever data the consumer loop may have been trying to write after the TDMS file was closed.

I can't tell what you sample rate or record length is set to from the screenshot. I think there might be a problem with the 1 second delay in your producer loop and the sample rate/record length but I'm not sure.

[christian1996]

The Oszilloscope settings were set to 100k record length and 100 kS/s so it measures a second and then it fetches the record. Therefore I set the loop timing to one second because otherwise the loop dont work. My thoght is because the measurment was simulated it didnt work.

[mj0541 · Accepted solution]

I think what is happening is expected based on your measurement configuration. It looks like you're using an Immediate trigger which will take a measurement, well, immediately and each fetch from memory almost certainly won't be in phase with the previous fetch. 

For how long does this measurement need to run? A few minutes or several hours? 

Also, what device are you using? If you're device has enough memory and the measurement duration is short enough, you might be able to capture the entire waveform in one single acquisition.

For example, if your scope has 8MB of memory and you're sampling at 100kS/s (assuming 8 bits per sample) then you could capture about 80 seconds at once.

My advice is to consider the nature of the waveform you're trying to capture and tailor the measurement configuration to the waveform. 

The following link may be helpful, Acquiring waveforms at hardware timed intervals ,and this link as well, Continuously acquiring data . There are some links at the beginning of the last document that might also be helpful.

Keep in mind that, due to the way oscilloscopes acquire data, you will almost certainly lose some data. 

[christian1996]

Thank you for your Help. It seems that if you simulate the Oscilloscope than it records and after the next fetch it starts from new. In the real system there are no drops in the voltage.