. Basic methods for the calibration of sonar equipment. BATTERY SUPPLY -e- T REC LINE CIRCUIT FOR li=135ClHMS 3A HYOROPHI 3A HYDROPHONE Figure 5. Circuit used in obtaining reference receiving response chart. 3A89 qB *m HYDROPHONE Figure 6. Circuit used in oljtaining receiving response chart, QB No. HI transducer. amplifier through the coupling amplifier, as shown in (b) of Figure 7. The two recorder traces are shown in Figure 8. The log sheet shows that both measure- ments were made with the same receiving ainplifier gain. Thus, the difference between the two traces gives the coup
. Basic methods for the calibration of sonar equipment. BATTERY SUPPLY -e- T REC LINE CIRCUIT FOR li=135ClHMS 3A HYOROPHI 3A HYDROPHONE Figure 5. Circuit used in obtaining reference receiving response chart. 3A89 qB *m HYDROPHONE Figure 6. Circuit used in oljtaining receiving response chart, QB No. HI transducer. amplifier through the coupling amplifier, as shown in (b) of Figure 7. The two recorder traces are shown in Figure 8. The log sheet shows that both measure- ments were made with the same receiving ainplifier gain. Thus, the difference between the two traces gives the coupling gain or loss. It will be seen that this loss is db at 25 kc. The generated voltage of the test instrument rela- tive to the \oltage of the 3A hydrophone across 135 ohms can now be computed as follows: Difference in receiving chart readings + (From Figures 2 and 3) Coupling loss for test hydrojibone + (From Figure 8) Difference in receiving amplifier gain — (From Figure 4) Difference in available power to projector ... 0 db (From Figure 4) Difference in testing distance 0 db (From Figure 4) -| With the calibration of the hydrophone standard (Figure 1) known, the receiving response of the test instrument may be obtained as follows: The response of the standard, according to Figure 1, is — db vs 1 volt for a sound field of 1 dyne per sq cm at 25 kc. The response of the test instrument, in accordance with the above computation, is db. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Office of Scientific Research and Development. National Defense Research Committee. Washington, D. C.
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