This suite of calibration services provide calibrations of the free-field sensitivity of miniature hydrophones of the type used to characterise medical ultrasonic fields. The services cover the frequency range 0.2 MHz to 60 MHz.

Calibration of a hydrophone over the frequency range 1 to 40 MHz

The service uses a multiple frequency technique based on non-linear distortion of an initially sinusoidal acoustic tone burst.

A comparison method is used in which the response of the test hydrophone is compared against a reference transfer standard hydrophone whose calibration is traceable back to the NPL Primary Standard laser interferometer. Hydrophone sensitivities are derived in the frequency range 1 to 40 MHz in integer frequency steps. Optimum sensitivity for the test hydrophones are in the range of 10nV/Pa to 1000nV/Pa, although calibrations can be carried out down to 5 nV/Pa but with expanded uncertainties which may be degraded significantly.

Best overall measurement uncertainties for hydrophones of typical response (i.e. sensitivities of greater than 20 nV/Pa from 1 MHz to 40 MHz) are 6% for 1 to 8 MHz, 7% for 9 to 12 MHz, 8% for 13 to 16 MHz, 11% for 17 to 20 MHz, 12% for 21 to 30 MHz and 15% for 31 to 40 MHz.

Average turnaround (see disclaimer): 3 weeks.

The following calibrations are available within this area:

• Calibration of a hydrophone over the frequency range 1 to 20 MHz
• High frequency hydrophone calibration up to 60 MHz
• Fine frequency calibration between 0.5MHz and 20 MHz
• Matching and calibration of a hydrophone/amplifier combination

Contact

Customer Service tel: +44 20 8943 8631
E-mail: acoustics_enquiries@npl.co.uk