A usability evaluation or test should be conduced for a new product to reveal potential usability problems and find possible solutions. A new digital notebook with a sensor and a pen was evaluated in this study. In this paper, we conducted an experiment to find out the effects of sensor positions on the correctness of signal receiving, and employed the protocol analysis method to elicit and identify usability problems of the digital notebook. Results showed that the sensor positions influenced the rate of correctness of signal receiving as well as the number of operational usability problems. Compared to the positions of on-the-top and on-the-left of the paper, the position of on-the-left-top of the paper was the best position with the highest correct signal receiving rate and the least number of operational problems.