NON-INVASIVE ULTRASONIC MEASUREMENT TECHNIQUE.
Transit-Time – When it comes to non-invasive ultrasonic flow measurements, TRANSIT-TIME and DOPPLER are the two most commonly used techniques. Both methods measure the flow of the medium using sensors which are clamped on the outside of the pipe or tube. The main difference between these methods is that they each work best in opposite situations.
Transit-Time flowmeters are used for clear liquids such as water, oil and chemicals. Please contact us for specific advice and information on whether this method is most suitable for your application.
Transit-Time – operation
Transit-Time flow meters measure the time it takes for an ultrasonic signal (sound vibration that is imperceptible to human hearing) to reach the other side of a pipe or pipe wall in a diagonal line. Both upstream and downstream time measurements are compared. Without flow, the transit-time would be the same in both directions. With a current or flow, the signal moves faster with the flow and slower against it. The measured time difference is directly dependent on the speed of the medium flowing through the pipe or tube. This transit-time difference is the relevant value to provide insight on the flow rate of liquids and gases.
Clear liquids and gases
Because the ultrasonic signals must cross the pipe/tube to the receiving sensors, the medium within the pipe should contain only a minimal concentration of air bubbles or solids (< 30%). At a higher concentration, the high-frequency vibrations are damped and therefore too weak to reach the other side of the tube wall. In that case, we advise you to opt for a doppler flow measurement.
Two sensors
In order to be able to set up a bi-directional ultrasonic flow measurement, we always supply our Transit-Time flowmeters with two sensors. Both can send and receive signals.
Very accurate (0,5 – 1%)
With the current generation of Transit-Time flowmeters, results are achieved with 0.5 – 1% accuracy on the actual value.
Widely applicable
Transit-Time flowmeters are suitable for pipes and tubes of different materials (including double-walled) and with a diameter ranging from 3 mm up to 6500 mm.
Applications: drinking water, cooling water, water / glycol solutions, hydraulic oil, heating oil and chemicals.
