Ultrasonic nullah flow meter

The physical quantity directly measured by the ultrasonic nullah flow meter is the liquid level. Used for open channel flow measurement, in the open channel installed in the water measuring weir tank. Measuring weir to the size of the flow in the nullah into the liquid level nullah flowmeter height.

The nullah flowmeter measures the water level in the water measuring weir, and then back-calculates the flow rate according to the relationship between the water level and flow rate in the corresponding water measuring weir. The correspondence between flow rate and water level in an ordinary nullah is affected by the slope drop ratio and surface roughness of the channel. Installation of water measuring weir in the channel, resulting in throttling effect, so that the flow and level in the nullah have a fixed correspondence. This correspondence mainly depends on the construction size of the water measuring weir, and the influence of the channel is reduced to **** small.

When the nullah flowmeter works, the ultrasonic sensor is fixedly installed above the measured liquid level. The probe transmits pulsed ultrasonic waves to the water surface. Sound waves through the air to reach the liquid surface, the sound wave is reflected by the liquid surface to become a reflected wave, the probe to receive the reflected wave is called the return wave. The calibration bar under the probe also produces reflections that are received by the probe as calibration waves. Nullah flowmeter according to the emission wave and the return wave, emission wave and the time difference between the correction wave to find the probe to the liquid surface distance. In and the probe to the water level zero liquid level distance L minus, that is, to find the liquid level height H. As shown in the figure.

Nullah flowmeter probe installed in the water measuring weir tank water level observation point position, measuring the water level flowing through the water measuring weir tank. In the nullah flowmeter installation, the corresponding water weir tank water level flow relationship in the form of a number of tables through the key into the instrument memory. Nullah flow meter microprocessor by the measured water level, using the table method to find out the corresponding flow value. The number between the two neighboring values in the number of tables, using linear interpolation to find out.