Open Channel Flow Measurement
The flow in an open channel can be calculated by measuring the liquid level or head (h) up stream of a standard weir of flume. Weirs and flumes increase the liquid inlet level to prevent the downstream discharge affecting the upstream liquid level measurement.


The more liquid that flows through an open channel the higher the level. In an open channel flow measurement the head of water measured is typically between 100 to 1000mm. The design of Flumes and weirs for open channel flow measurement has been standardised to achieve a reliable and accurate level measurement which is required to measure an open channel discharge. Open channel flow measurement is applied in a number applications including:

Rain water or Storm water
Raw water discharge
Industrial and municipal wastewater
Effluent and sewer measurement
Flow measurement of rivers and streams

Different types of level measurement are available including Ultrasonic, Microwave, Float, and Hydrostatic pressure. The ultrasonic method is now very popular as it is non-intrusive and low maintenance. The Ultrasonic flowmeter transmitter emits a sound pulse which is then reflected back from the surface of the liquid to be measured. The flowmeter transmitter measures the flight time and can calculate the instantaneous flow and the totalized flow.

LTH Electronics offer Ultrasonic transducers and transmitters for open channel flow measurement in flumes or weirs. The Flowmeter is a compact Ultrasonic transmitter for open channel flow measurement, with a 4-20mA output for instantaneous flow transmission, two relay outputs for impulses/ volume transmission and set point or diagnostic alarm functions and a MODBUS RTU output. The Swing controller takes up to 2 sensor inputs, has 5 relay outputs and can display both the Instantaneous and the Totalised flow.

Both the Flowmeter transmitter and Swing controller are suitable for use with Venturi, British Standard or Parshall flumes and have pre-programed flume dimensions simplifying the setting up procedure.

Call us on +44 (0)1582 593693 or email to find out how we can help you.