Mainstream uses the area-velocity method to measure the liquid flow rate.
A submerged pressure transmitter or ultrasonic sensor determines the liquid level, and Mainstream calculates the flow cross-sectional area from a stored description of the pipe or channel geometry.
The Mainstream velocity probe operates immersed in the flow and projects two ultrasonic grid patterns into the moving liquid. Bubbles and solid particles carried by the flow act as tracers, reflecting ultrasound back to the probe as they pass through the two grids.
Mainstream measures the time for tracers to travel between the two grids. Dividing the grid separation by the travel time gives the tracer velocity.
Hundreds of tracer velocity measurements are accumulated as a velocity histogram. Analyzing the histogram gives the mean flow velocity.
The liquid flow rate is the mean flow velocity multiplied by the flow cross-sectional area.
A unique feature of the Mainstream is its signal quality reading. This is the percentage of the tracer data that Mainstream is able to process into velocity measurements. The signal quality is an invaluable metric for flowmeter condition monitoring.