Effect of digital acquisition on the complexity of chaos

The effect of data acquisition on the complexity of chaos using permutation entropy has been studied experimentally and numerically. The complexity of chaos is quantified using the normalized permutation entropy at the feedback round-trip time. Two "abnormal" variations of the complexity of chaos with bias current have been observed experimentally. The different vertical scales of the oscilloscope in data acquisition are attributed to this abnormal change. The method to remove the effect of data acquisition has also been proposed.