Sewer Doppler Flowmeter Fails to Measure Flow [Dayu Electronics]

　　   1. Time: December 14, 2022

2. Location: Suiyang County, Hangzhou

3. Products used: Low-power manhole level meter and sewer Doppler flowmeter (velocity meter + battery + host + wireless RTU)

4. Application scenario: Urban sewer system

5. On-site condition and solution: The sewer flowmeter could not detect flow, and remote wireless data transmission was incorrect. After opening several manhole covers on-site, we identified the installation issue: the water level did not submerge the sensor of the ultrasonic Doppler velocity meter, so it could not measure flow velocity, and the flow rate was therefore 0.

The sensor should be installed as close to the bottom of the channel as possible. If there is a lot of sediment, sludge, aquatic weeds, or rolling stones at the bottom, the installation height can be raised to prevent the probe from being covered by sediment or weeds, or being struck by stones.

The sewer Doppler flowmeter should be installed in a location with steady water flow. In areas where the flow is unsteady, it is usually turbulent. Under turbulent conditions, the measured flow velocity fluctuates, is unstable, and the error can be significant. The water level for the Doppler velocity meter must be 15–20 cm above the device.