15
5 Measuring the sound velocity
5
Measuring the sound velocity
5.1
General information
It is required to measure the sound velocity since only correctly
entered sound velocity values ensure precise measurements.
The sound velocity values are taken from an internal
table, see
section 7.6.7. However, the sound velocity values entered under
Pipe data are only approximate values. Apart from that, it may
also be possible that you do not know the pipe dimensions or
material.
This function requires a noise source:
You can use an opened hydrant, for example,
z
which generates a clear display in the correlation-function field,
z
thus being „correlatable“,
whose location must be known,
z
whose location should not lie in the central range of the mea-
z
surement section, in order to increase the measuring preci-
sion.
If the measurement section consists of varying pipe sections (dif
-
ferent materials or
dimensions), the sound velocity
measurement
will lead to incorrect results.
5.2
Performing a measurement
The measurement procedure is very similar to that of correlation
measurements.
First, connect microphones and
z
radio transmitter as described
in section 2.2).
Enable option Sound velocity in
z
menu Measurement method
(see section 7.5).
Select Pipe data and enter the corresponding data.
z
Under Artificial leak, enter the distance between the artificial
z
leak and microphone 1: if it lies outside and beyond the mea
-
surement section
of microphone 1, enter 0 m as distance,
–
of microphone 2, enter the entire length of the measurement
–
section under distance (i.e., the „pipe length“).
