Using a Radar Level Sensor for Flow Measurements

By on August 16, 2010


Fondriest Environmental water level monitoring stations can be equipped to measure water level in a number of ways. These readings can be used with a water flow rating curve to estimate flow continuously. Level is measurable either with a pressure, bubbler, or non-contact radar level sensor. A radar level sensor is an ideal choice when a bridge or above-water structure is available for mounting. Unlike other level monitoring systems, the entire radar system is safe from any debris since it can be mounted far above the water.

Radar level sensors can mount to a bridge, frame, pipeline, or extension arm above the water and determine level based on its distance from the water surface. Antennas transmit and receive pulses to and from the water surface. The transmitting antenna transmits short radar pulses, and the receiving antenna receives the pulses reflected from the water surface. The time delay from transmission to receipt is proportional to the distance between sensor and water surface.

Radar Level Sensor Technology

Historically, radar level sensors have not delivered the same accuracy as bubbler sensors or pressure transducers. The OTT RLS non-contact radar level sensor, however, uses an advanced non-contact level measurement technology, which provides the USGS accuracy requirement of +/-0.01 feet with a non-contact measurement distance range of up to 115 feet to water.

The pulse radar technology is ideal for monitoring in remote areas and applications where conventional measuring systems are not suitable. The sensor is IP67 waterproof and has extremely low power consumption, making it ideal for solar-charged monitoring systems.

Two antennas are enclosed in a compact housing and transmit pulses toward the water surface. A sampling rate of 16 Hz (16 measurements/second) with 20 second averaging minimizes water surface conditions such as waves and turbulence. The OTT radar level sensor does not require calibration and is unaffected by air temperature, humidity, flood events, floating debris, or contaminated water.

The sensor includes built-in RS-485 and SDI-12 outputs for interfacing with NexSens iSIC and SDL data loggers. Sensor cable can be factory-connectorized with NexSens underwater connectors for integration to an SDL submersible data logger sensor port. Data collection options include direct-connect, landline phone, cellular, radio, Ethernet, WI-FI, and satellite telemetry. NexSens iChart Software, a Windows-based program for interfacing both locally (direct-connect) and remotely (through telemetry) to a NexSens data logger or network of data loggers, is also available for radar level monitoring systems.

To learn more about radar level sensor features or other water level monitoring technology, call a Fondriest Environmental application engineer at 888.426.2151 or email

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