The Acoustic Open Tank Facility (OTF) of the Naval Undersea Warfare Center (NUWC) Division Newport is a primary test facility for prototype acoustic evaluation of underwater devices. The OTF features a large open water tank, a fully automated data gathering system, and associated mechanical support equipment. The OTF can measure the acoustic characteristics of sonar system components, including (but not limited to) transducers, hydrophones, small arrays, baffles, and windows. The OTF has the capability to perform extensive acoustic, mechanical, and electrical measurements. A six channel Transducer and Hydrophone Acoustic Measurement and Evaluation System (THAMES) provides the OTF a fully integrated, computerized, automated acoustic test setup, control, data gathering, and analysis capability. THAMES is a Windows NT system based on LabVIEW. THAMES integrates control and measurement software with sophisticated Hewlett Packard (HP) VXI data gathering modules and all required supporting instruments and controls.
Features
Drawing of the tank showing the basic configuration with a cutaway view of equipment during test in the water.The OTF's primary test tank measures 9.14 meters long, 4.57 meters wide, 4.57 meters deep, holds 204,390 liters, and is of concrete construction. The OTF's mechanical support equipment can handle test specimens up to 450 kilograms and rotate specimens to a computer controlled accuracy of ± 0.1 degree.
Measurement Capabilities
Measurement capabilities of the OTF include (but are not limited to): transmitting response measured for voltage, current, and power; free field voltage sensitivity (FFVS) for receivers; and complex impedance. Directivity patterns can be supplied for receivers and transmitters along with accurate measurement of harmonic distortion of transmitted and received signals. OTF capabilities also include measurement of ambient noise levels, spectrum analysis of acoustic response, linearity (transducer output versus input power); bearing error for multi mode hydrophones; sum difference (null balance) magnitude and phase; and absolute reciprocity calibration. The OTF can measure capacitance and dissipation factor, direct current resistance, and insulation resistance for all devices tested.
The OTF's operational capabilities cover the frequencies of 1 kHz to 3 MHz with a dynamic range of 100 dB. Transmit control parameters including pulse width, pulse repetition, and transmit signal delays, and a range of available amplifiers (up to 5 kVA), enable custom defined drive specifications. The OTF performs digital signal processing on acquired data with measurement analysis that includes (but is not limited to): Fast Fourier Transforms (FFT), spectral analysis with averaging, and various complex magnitude computations.
Calibration Memoranda
Calibration data is available at the time of the measurement in hard copy and/or electronic format. Formal calibration memoranda may also be produced, upon request, that include presentation quality graphical and tabular outputs.
Special processing to include data overlays, normalization of data outputs, comparison with nominal levels, or other specific processing can also be accomplished. MS EXCEL compatible data files are standard system outputs; depending upon classification level, this data may be made available via the Internet.
Contact
For questions or assistance in obtaining measurement services, please contact the Acoustic Open Tank Facility Head at:
nuwc_npt_usrd_open_tank@navy.mil