English: A Dumas Neyrpic water current meter with propeller, made in France. This horizontal-axis instrument is used for measuring water velocities between 0.2 and 2.4 metres/second. An array of these devices can be used for hydroelectric turbine flow measurements. A single device can be lowered on a wading rod and used to measure flow in a stream or an ocean current. The number of the revolutions of the propeller is proportional to water velocity and is counted electronically. This style of instrument has a cosine response to off-angle water currents.