Experimental study of the input parameters of the data acquisition device NI USB 6009

The error of method appears when measuring voltage by data acquisition (DAQ) devices because of neglecting their input parameters. The experimental determination of input parameters, such as the equivalent Thevenin input voltage and resistance, for 9 DAQ devices NI USB 6009 was carried out. Uncertainties for these parameters are given as well. The experimentally determined parameters compared with that given in the device documentation.