Flow Measurement using Transit Time Method

Flow Measurement using Transit Time Method

Transit Time Method

  • For clean to slightly polluted media
  • Complies with IEC 60041/EN ISO 12242/EN ISO 6414
  • Very high measurement accuracy


Average flow velocity and flow cross section are required to determine the flow Q. This leads to the general formula:

Q = v (average) • A

The flow cross section A is determined by continuously measuring the filling level taking the channel shape as well as the channel dimensions into account.
The average flow velocity within the flow cross section is determined by using the velocities found in one or more measurement paths. The higher the number of measurement paths used, the higher the measurement accuracy.


Your Benefits

  • Single-path or multi-path measurement
  • Great range of sensors, suitable for each application
  • Our measurements comply with EN ISO 6416 and IEC 60041

The NivuFlow 650 measurement principle is based on detecting the transit time of ultrasonic signals between two sensors (A and B).
The transit time in flow direction t is faster 1 than it is against the flow direction t . The 2 time difference between both transit times is proportional to the average velocity along the measurement path v .

The measurement system calculates the average cross sectional area velocity v , A the average path velocity v and the m results are indicated directly on the transmitter display.

Functional Principle of Flow Measurement with Transit Time Method

Measurement in Pipes

For full pipe measurement applications with a fully developed velocity profile it is normally sufficient to use a single velocity path measurement (1E1P).
However, normally there are distorted flow profiles which have negative effects on the measurement accuracy. Such influences can be compensated by using up to 32 measurement paths. Depending on the application different transducer models work best. For measurement in part full and full 
pipes special screw-in or pipe sensors ensure a simple installation solution.

Measurement in open channels

Transit time is a well understood and established method for flow measurement in demanding applications without requirement for the construction of a measurement structure such as weir or flume.

To meet the highest possible accuracy requirements for both open channel and pipe measurement applications it is currently possible using up to 32 velocity paths. 

NIVUS have developed a range of highly accurate acoustic transducers, with both standard and bespoke mounting systems available to ensure the best and most flexible installation options are available for any measurement application in part filled channels or in rivers and streams. 

Level Measurement (h)

Accurate flow measurement requires precise and reliable determination of levels under all hydraulic conditions which is achieved by using 0/4 - 20 mA level sensors. For such cases use either contactless ultrasonic sensors such as „i-Series“ sen­sors or hydrostatic sensors such as NivuBar Plus.

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