英语语法分析

Check oxygen concentration by a refractometer.

用折射仪测量一下氧气的浓度。

Calibrate the refractometer with water and press the Zero button.

校准折射水，并按下零按钮。

Actual humidity measurements in the boundary layers have been made with a microwave refractometer.

实际上已经用微波折射仪测定了边界层中的湿度。