Page 42 - HydrophoneHandbook_eReader_Ed2_20151208
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Hydrophone Handbook

               8. Calibration

 8.1 Introduction
 An acoustic calibration of a hydrophone determines the
 sensitivity as a function of frequency. This is measured in terms
 of units of electrical output (volts) per unit of physical pressure
 (Pascal) over a frequency range (Hz). These fundamental units
 provide a reference for the calibration and allow different
 measurements to be compared.
 The calibration methods are well defined and accepted
 internationally, while the accuracy of the calibration is carefully
 determined with a known uncertainty.
 Traceable calibrations mean the calibrations are reliably traced
 back to a primary calibration laboratory, such as National
 Physical Laboratory (NPL) in the United Kingdom or Physikalisch-
 Technische Bundesanstalt (PTB) in Germany.

 8.2 Why Calibrate?
 Calibrations should be done:
 • To make sure measurements are accurate and comply

         with standard methods that are universally accepted
 • To verify the accuracy and stability of the measurement

         system
 • To account for local test conditions such as temperature

         variations
 • Ultimately, to create confidence in measurement results

 8.3 How often?
 Typically hydrophones are calibrated once per year.

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