Ultrasonic flow meters work largely independently of the specific properties of the product to be measured, such as pressure, temperature, viscosity or conductivity. Due to these advantages, they can be used in a wide range of applications. A further advantage of these systems is that they have no mechanical parts and are therefore less susceptible to maintenance than other flow meters.
Principle of ultrasonic measurementThe basis of ultrasonic-based flow measurement is a system consisting of two sensors that communicate directly with each other. In accordance with DIN standard 1319, the flow measuring device consists of two parts: the actual measuring sensor in the form of the ultrasonic sensor and the measuring transducer or transmitter as the evaluation unit.
For the measurement, an ultrasonic pulse (sound waves) is sent between the two sensors through the medium to be measured in a pipe. The transit times in the direction of flow and against the direction of flow are measured continuously.
It measures the difference in the transit time of these pulses in the direction of flow and against the direction of flow.
Without water flow, the signal propagation times in the flow direction and vice versa are identical. If water flows through the measuring section, the propagation speed of the sound waves is accelerated in the direction of flow and delayed in the opposite direction.
The transit time difference between the two ultrasonic waves of a data pair is directly proportional to the average flow velocity. To determine the flow volume in relation to a defined period of time (second, minute, hour), the average flow velocity is multiplied by the respective pipe cross-section of the sensor used. The so-called transit time difference method is a proven and widely used measurement method in industrial environments for recording flow volumes.
As a result, the meter displays the exact water consumption, regardless of whether the flow rate is high, low, constant or variable.
When using ultrasonic flow meters, which work on the basis of the transit time difference method, it is important to ensure that the medium to be measured is as homogeneous as possible and only contains a very small amount of solids or gas.
