M. P. Fodch 115 
1) Générateur Bruel et Kjcer 5) Boite d'accord des transducteurs 
2) Fréquencemetre Rochar 6) Diviseur T.H.T. 
3) Impulseur-cadenceur 7) Voltmetre Philips 6015 
4) Ampli puissance Jaubert 8) Ampli réception 
(500 w en régime continu 9) Philips 6017 
| kw en impulsion) 10) Oscillo double trace Cossor 
Fig. 6.12. Instrumentation for response measurements. 
Réception i) 
Emmission T 
T,) Transducteur emetteur qT Ty 12) Transducteur récepteur 
1) Générateur Bruél et Kjoer 7) Ampli 
2) Impulseur 8) Voltmetre Philips 6017 
3) Thermocouple TH} 9) Découpeur 
4) Fréquencemetre Rochar 10) Oscillo a double trace Cossor 
5) Voltmetre Philips 6015 11)  Enregistreur Bruél et Kjcer 
6) Voltmétre Philips 6010 
Fig. 6.13. Stand for reciprocity calibration. 
and Z is obtained by measuring e, and l, R by measuring e, ande,. The block 
diagram in Fig. 6.13 shows the instrumentation used for these measurements. 
6.2.3.1. Calibration by Comparison 
This is a much simpler calibration procedure than the reciprocity method. 
We have only to compare the transducers tobe calibrated with a standard model. 
6.2.3.2. Directivity Measurements 
The tank instrumentation furnishes a polar plot of received pulses in db level 
as a function of transducer bearing and frequency. A 360° directivity diagram 
can be plotted in two minutes. For special purposes, in order to get complete 
details about a transducer, we have had to carry out up to 500 directivity meas- 
urements for different aspect angles in bearing and tilt and at different fre- 
