Manuale di Istruzioni
Instruction Manual
58-E4800 Rev. 4 EN 21/05/2012
3.3.2 Path length and pulse velocity measurement
For direct transmission, the path length is the distance between the transducers and when
possible, the accuracy of measurement of the path length should be ± 1% and the
accuracy shall be recorded.
For semi-direct transmission, it is generally found to be sufficiently accurate to take the
path length as the distance measured from centre to centre of the transducer faces.
The accuracy of estimating of path length is dependent upon the size of the transducer
compared with the centre to centre distance and it shall be estimated.
For direct and semi-direct transmissions the pulse velocity shall be calculated from the
formula:
where:
V = pulse velocity, in km/s
L = path length, in mm
T = time taken by the pulse to transverse the length, in ms.
The resultant determination of the pulse velocity shall be expressed to the nearest 0,01
km/s or to three significant figures.
With indirect transmission there is some uncertainty regarding the exact length of the
transmission path, because of the significant size of the areas of contact between the
transducers and the concrete. It is therefore preferable to make a series of measurements
with the transducers at different distances apart to eliminate this uncertainty.
To do this, the transmitting transducer shall be placed in contact with the concrete surface
at a fixed point “P” and the receiving transducer shall be placed at fixed increments “X”
along a chosen line on the surface. The transmission times recorded should be plotted as
points on a graph showing their relation to the distance separating the transducers.
Fig. 3-10
determination by indirect
(surface) transmission
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