Synchronize analog data

[RudiRocker]

Hello,

how can I synchronize data coming from an external USB device and DAQmx? The DAQmx is buffered, sampling with a sample rate of KHz and the sampling rate of the USB device is varying and between 4 to 6 kHz. The data of the USB device is provided by another vi and can be read by a global variable. I would like to have a second vi which reads the data from the global variable and synchronize it with the data from the DAQmx. How can I implement this?

A sample vi which should clear things out is attached.

[crossrulz]

Does the USB device give a timestamp for when a sample was taken (like DAQmx does)?  Other than that, you need some kind of signal on both devices to be able to synchonize properly.

Furthermore, use a queue instead of a global variable.  Use a queue so that you don't lose data.

[RudiRocker]

No, unfortunately the USB device does not give a time stamp.What kind of signal could I use? I just have a sensor which outputs an analog voltage which is acquired by the DAQmx and the USB device giving some measurement values taken at arbitrary times with a rate between 4 to 6 KHz. I could implement some trigger inside the USB readout VI to tell me when a sample is taken?

How can I sample the global variable with a specific sample frequency?