基准零点 meaning in Chinese

reference datum

B . all undimensioned features shall be located within a tolerance of . 005 from datum zeroo
所有未注的特征相对于基准零点的位置偏差须在0 . 005之内
Acoustics - reference zero for the calibration of audiometric equipment - reference equivalent threshold sound pressure levels for pure tones and supra - aural earphones
声学.音响设备校正基准零点.纯音和超听觉耳机用基准等效阈值声压级