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Hydrophones that are used well below their first resonance and are small compared to a wavelength are best calibrated in air at a low frequency. GeoSpectrum’s hydrophone calibrator combines high accuracy with a high throughput, making it ideal for high-volume production. One operator can calibrate 200 hydrophones per hour; two operators can calibrate 400 hydrophones per hour. The same calibrator can be used to determine the pressure at which switch closure occurs on hydrophones, such as the M2E, that require a switch to qualify for export to certain countries.

Acoustic Calibrations

Parameters measured Voltage sensitivity
Lead-to-lead resistance
Calibration accuracy ± 0.2 dBV (NIST traceable)
Repeatability ± 0.1 dBV
Quantity calibrated per cycle 10
Throughput 200/hour with one operator
400/hour with two operators
Measurement medium Air
Measurement temperature Ambient
Pressure Ambient (1 bar optional)
Measurement frequency 26 Hz
Dynamic pressure amplitude (rms) Adjustable, but typically 1 mbar
Data recorded (written to database) Serial number
Date and time of calibration
Voltage sensitivity
Capacitance and dissipation
Charge sensitivity (calculated)
Lead-to-lead resistance
Calibration chamber volume Typically 1000 cc, other sizes available

Switch Closure

Parameters measured Pressure at which switch closes
(expressed in metre depth)
Accuracy Typically 1/3 psi. Greater accuracy can be achieved at the expense of throughput
Throughput 200/hour with one operator
Measurement medium Air
Measurement temperature Ambient
Pressure User adjustable from 0.5 bar to 6 bar
Data recorded (written to data base) Date and time
Switch closure depth