What type of instruments are used to measure flow depths?

Flow depth measurement instruments are specifically designed to capture the water level or depth of flow in various applications, such as wastewater treatment or environmental monitoring. The correct selection includes bubblers, capacitance probes, floats, pressure sensors, and ultrasonic transducers, which all offer effective means to measure flow depth accurately.

Bubblers work by releasing air through a submerged pipe to create a pressure that corresponds to the depth of water above the outlet. Capacitance probes detect the change in capacitance caused by the dielectric properties of water, and floats provide a mechanical way of gauging depth by rising and falling with the water level. Pressure sensors measure the hydrostatic pressure that water exerts at a specific depth, while ultrasonic transducers gauge distance by sending sound waves that reflect off the water surface, allowing for precise height measurements.

Other listed instruments do not serve the purpose of measuring flow depths. For instance, thermometers and barometers are used for temperature and atmospheric pressure measurements respectively, while simple rulers and gauges may not provide the precision or capability required for flow depth. Wind vanes and anemometers are specifically designed for measuring wind direction and speed, making them irrelevant in the context of measuring flow depths.