gas density gauge

例句：

1. 1.The gas density gauge is used to measure the concentration of gases in a sample.
   气体密度计用于测量样品中气体的浓度。
2. 2.The gas density gauge was used to determine the composition of the gas mixture.
   气体密度计被用来确定气体混合物的成分。
3. 3.The gas density gauge was used to monitor the level of gas in the pipeline.
   气体密度计被用来监测管道中气体的水平。