How to check the sampling rate of a Data Acquisition device?
Use a function generator with a known frequency square wave, for instance 1kHz, and measure how many points you have on a full cycle, should be 100.

If you don't have a function generator, you can use a small optical sensor like photodiode or shorted solar cell and measure the flicker of the light, as it is a known 50 or 60Hz depending on the country you are in and count the number of points you have for a full wave.