The Sound Velocimeter at Sea-Performance and Limitations
Abstract
The design and operation of a precision in situ depth-temperature- sound-speed measurement system containing two velocimeters is described, including procedures used to ensure reliability and accuracy of results. Two instruments side-by-side make any irregularities in the operation of the velocimeters evident. Using different pairs out of three instruments at successive stations identifies both the error and its source. The individual readings can then be corrected to improve accuracy and confidence in the final result, the average of the two instruments. Extensive field use showed the velocimeters to be reliable 90-95 percent of the time the two instruments were tracking to within 15 cm/sec. Occasionally erratic behavior is observed; some cases are undetectable using only one instrument. Among the irregularities in the operation of a velocimeter are the following: changes in calibration after field use; the 15-cycle jump; persistent, pressure-dependent calibration errors in some instruments; and sporadic short periods of instability when submerged in regions of rapid temperature change. An analysis of error sources and magnitudes shows the susceptibility of delay time to thermal transients. A comparison between Nansen bottles and velocimeters shows the accuracies of derived sound speeds to be similar, the velocimeter yielding continuous data and being more suitable for surveys, or microstructure work.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1966
- Accession Number
- AD0805095
Entities
People
- Ants T. Piip