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Hydrophone Handbook

           10. Troubleshooting

 Anomalous Signal Observed cont.
 2. Place the hydrophone far enough away from the source to

      make sure that any electrical interference has ended before
      the arrival of the acoustic signal
 3. Confirm the acoustic signal by moving the hydrophone.
      The acoustic signal should change, whereas an electrical
      signal will not.
 4. Check all connections are secure, particularly the ground
      connection.
 5. Check to make sure transducer is insulated. Make sure the
      water resistivity comply with standard requirements.
 6. Determine if the anomaly is intermittent or repeatable.
 7. Check hydrophone quality (e.g., electrode intact,
      mechanical integrity, exterior film)
 8. Check the terminating impedance into the oscilloscope. In
      general, Onda hydrophones with a preamplifier should be
      connected to the oscilloscope with a 50 Ω impedance. If
      an Onda hydrophone is connected directly to a oscilloscope
      it should be connected with a high impedance, typically 1
      MΩ in parallel with 10 to 30 pF. See Section on Connecting
      Your Hydrophone.
 9. Determine if the environment has excessive electrical noise
      and whether the source is sufficiently shielded.
 10. Confirm the hydrophone in use has sufficient signal to
      noise.
 11. Determine if environmental interference is present by
      removing the hydrophone from the acoustic field and
      observing the signal. Similarly, you can disconnect the
      hydrophone entirely.

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