A depth finder is useful to locate structure, but not necessary.

找到结构，很有用，但不是需要深度仪。

Based on the principle of mass balance, the Pseudo-Level Depth Finder can attain the true level by testing annular gas rate.

根据物质平衡方法设计的拟液面测试仪，可通过测试油井环空排气量来确定油井的真实液面。

Laser detecting mine and laser depth finder, etc are testing and trying out laser weapon on board, laser communication and laser gyro are demon...

而舰载激光武器、激光对潜通讯和激光陀螺等还处在论证、试验阶段。

With help of a sonic depth-finder a proper shoal gets detected and the fishermen prepare special devices which look something like spinnings and attached to the handrails.

用超声波探测器可以定位鱼群，渔民们准备一种特别的装置：看起来象连着扶手的陀螺。