When data are collected, the user can observe real-time measurement of data. At this time, the function to insert characters as if writing down a memo is called event setting. For example, when the condition of a subject changes in such cases that the subject tosses about or falls asleep, it is possible to mark an event at that moment. Once the events are marked in this way, various information can be obtained for convenience of analysis when data collection is over and the data are analyzed.