PROBLEM TO BE SOLVED: To provide a medical knife capable of determining quality of a drive signal by a drive signal within one drive cycle.SOLUTION: A liquid injection device 1 includes: a drive waveform forming part 29 for outputting a drive signal for driving a piezoelectric element 45 at a prescribed drive cycle 55 and a waveform examination part 31 for examining a waveform of the drive signal. The waveform examination part 31: compares a first determination value 56 and a second determination value 57 smaller than the first determination value 56, with a drive signal represented by a first signal transition line 54 counts a first number of times as the number of times when the drive signal ascends within the drive cycle 55 and passes the first determination value 56, and a second number of times, as the number of times when the drive signal descends and passes through the second determination value 57 when both of the first number of times and the second number of times are one time, determines that the drive signal is normal and when one of them is the number of times other than the one time, determines that the drive signal is abnormal.SELECTED DRAWING: Figure 5【課題】1つの駆動周期内の駆動信号で駆動信号を良否判定できる。医療用メスを提供する。【解決手段】液体噴射装置1は、所定の駆動周期55で圧電素子45を駆動する駆動信号を出力する駆動波形形成部29と、駆動信号の波形を検査する波形検査部31と、を備え、波形検査部31は第1判定値56及び第1判定値56より小さい第2判定値57と第1信号推移線54が示す駆動信号とを比較し、駆動周期55内に駆動信号が上昇して第1判定値56を通過する回数である第1回数と、駆動信号が下降して第2判定値57を通過する回数である第2回数と、を計数し、第1回数と第2回数とが共に1回であるときに駆動信号を正常と判定し、少なくとも一方が1回以外のときに駆動信号を異常と判定する。【選択図】図5
