Abstract—Useful for lecturers to gather real-time online feedback from students in a large lecture environment. Nevertheless, the fast pace of a lecture relative to a large audience can make it difficult for the lecturer to process and respond to large amount of feedback in real time. To address this issue, we propose a mobile digital backchannel system ClasSense that allows students to express their emotions during a class and analyses the sentiments of their feedback in real time so that the lecturer can continuously monitor the morale of the student population and respond to the most important concerns students have in common. This paper presents the key design considerations and a pilot study of the proposed system.