Direct primary calibration of various types of Hydrophones from 0.5 MHz up to 100 MHz

Abstract

A measurement setup for the primary calibration of hydrophones was compared to a secondary calibration setup. In the past, the primary calibration setup was used at PTB (Physikalisch-Technische Bundesanstalt) only for the calibration of reference hydrophones; these reference hydrophones were then used in the secondary calibration setup for a calibration service on submitted hydrophones. Plans exist for directly using the primary calibration setup in the future for the calibration service, as this will be faster and will reduce the uncertainties of the results. To integrate different types of hydrophones into the primary calibration setup, a broad range of adapters were designed and fabricated by means of 3D printing. A capsule-type hydrophone and a needle-type hydrophone were compared. For both hydrophones, the results of both methods showed good agreement in the frequency range up to 45 MHz. Deviations at higher frequencies were determined to originate from the secondary calibration setup. With the primary calibration setup, the frequency range can be extended.