Abstract: To monitor the drainage flow by caisson volume method, a caisson linking with the bottom of the drainage ditch is installed. During off-hours, the caisson is a storage well, and the ditch water flows to the downstream through the caisson. Main equipment of the monitoring system includes a submersible pump, a two-float liquid level switch, as well as control and measuring single-chip microcomputer. During working time, the water stored is pumped out until it drops to the lower float liquid level switch, then all the ditch flow goes into the caisson, indicating another water storage process. By measuring the volume between the upper and lower float liquid level switch as well as the time of filling-up, the flow rate of the drainage ditch can be obtained. After the caisson is fully filled, the ditch water flows through the upper part of the caisson and gets back to normal drainage.

Key words: flow observation, drainage flow, caisson structure, pump control, float switch, single-chip microcomputer

摘要： 排水沟流量沉井式容积法监测系统的结构特征是在排水沟底部设一个与之相通的沉井，不观测时沉井为蓄水井，沟内水流通过沉井处流向下游侧。该监测系统主要设备包括潜水泵、双浮子液位开关以及控制和测量单片机等。需要进行排水沟流量观测时，先抽排沉井中的蓄水至低位浮子液位开关，然后自动停止抽水，排水沟的来水全部流入沉井，形成由井底向上的再次蓄水过程，通过测量流入沉井双浮子液位开关之间容积所花费的时间，计算确定排水沟的实际流量。沉井蓄满水后，排水沟的来水从沉井上部流过，恢复排水沟的正常流通。

关键词: 流量观测, 排水沟流量, 沉井结构, 水泵控制, 浮子开关, 单片机