In these times of increased labour costs, new electronic methods of monitoring open channel flows have come to the fore. There has been a shift in focus from open channel flow monitoring to ultrasonic sensors and hydro-static pressure sensors.
Open channel flow monitoring is the traditional technique for measuring water flow rates in irrigation channels, streams, and storm water systems; and for monitoring the effluent discharge in wastewater management.
This old method usually involves the use of weirs and flumes. The flow rate is calculated by measuring the change in the height of the water in the channel (with a simple vertical water level ruler).
Of course, this method relies upon human measurement and regular maintenance – blockages from debris and logs always need to be cleared to ensure accurate readings.
In contrast, the use ultrasonic sensors and hydro-static sensors is far less labour intensive and eliminates the need for regular maintenance.
Dwyer Instruments offers ULF Series Ultrasonic Flow Transmitter as an ideal sensor for monitoring open channel flow. The ultrasonic signal of the ULF sensor provides a non-contact measurement of flow which eliminates the need for maintenance.
In addition, the 4 mA to 20 mA transmitter output can feed back to a local panel meter, telemetry system or SCADA network for remote flow monitoring rather than checking the reading locally.
Another option for open channel flow monitoring is Dwyer's PBLT2 Series Submersible Pressure Level Transmitter. Through careful positioning, the sensor can provide an accurate 4 mA to 20 mA transmitter output of level reading based on height of water (pressure).
Even when placed directly into the channel, its ‘bird cage’ design and large diaphragm allow it to resist sediment build-up and debris fouling.