PeakSonic M1,M1-W,M3 series is a handheld portable bladder volume instrument, which can be applied in the department of Surgery, Emergency, ICU, Obstetric, Gynecology, Radiotherapy, Home and Nursing home. It provides the basis for clinical catheterization, evaluates the post-void residual after patient urination, and helps to make auxiliary diagnosis on the bladder and kidney diseases. It is also suitable for patients of lower body disability or loss of auto-urination function, to confirm the proper timing of urination.