User's Manual

Sound velocity measurement
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10 Sound velocity measurement
The Correlux C-3 system can be used to perform a sound velocity measurement in
order to determine the actual speed of sound in a pipe section.
This function is useful when no reliable information on the pipe material is available for a
pipe section or the entire measurement area. The calculated sound speed is then
accepted by the Correlator and used for the correlation.
The calculation of the speed of sound is possible in both the Online measurement as
well as the Offline measurement mode.
10.1 Velocity measurement in Online measurement mode
The Velocity measurement function compares the measuring values of the
Power transmitters while they are recording the noise from one specific source. The
sound velocity in the pipe is calculated using the sound delay.
There must be a source of noise on the pipe, which is clearly measurable for both
sensors. If such a noise source does not exist, it must be created artificially, for
example, by opening a fire hydrant.
The following conditions must be met in order to use the function:
x Two Power transmitters (PT-A and PT-B) at two measuring points.
x The distance between the two measuring points must be known.
x The noise must be clearly measurable for both sensors.
x The source of noise may be inside or outside the measuring section.
x The source of noise should not be half way between the measuring points.
x If the source of noise is inside the measuring section, the distance from the first
measuring point to the sound source must be known.
Requirements
Source of noise
distance
distance
Measuring point 2Measuring point 1