Benthic Acoustic Stress Sensor (BASS):
Electronics Check-Out Procedures

U.S. Geological Survey Open File Report OF-93-722

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The following is a series of test and calibration procedures for the Oceanographic Instrument Systems (OIS) Benthic Acoustic Stress Sensor (BASS). Although these procedures were written for a BASS system with a Tattletale 4 microcomputer, they should generally apply to those BASS systems with Tattletale Model 5 microcomputers.

Please send any comments or corrections to Marinna Martini at the U.S. Geological Survey, or to the address on the cover of this report.

List of Abbreviations

CCW counter clockwise
div division
DT-V differential time-voltage (circuit board)
m meters
ma, mA milliamps
MHz megahertz
ms milliseconds
mv, mV millivolts
ns nanoseconds
pf picofarads
p-p peak to peak
s seconds
V, v volts
VDC volts, direct current
us microseconds

I. Summary

The procedures described here are presented so that a technician with limited experience with BASS can perform basic tests which, when executed properly, should be a thorough evaluation of the health of the system. This is not intended as an in depth explanation of how BASS works. Should any significant problems be found, it is suggested that you contact the manufacturer, Oceanographic Instrument Systems, North Falmouth, MA. The Tattletale controller is manufactured by the Onset Computer Corporation, Cataumet, MA.

II. Recommended Test Equipment

The following equipment was used to perform the electronics evaluations described in this report. Models used at USGS test facility are given as examples other equipment with the same specifications may be substituted: 1. Hewlett Packard Model 54601A 100MHz Oscilloscope: Featuring four channel inputs, delay time and memory for trace storage and recall. This scope does not have a separate, external trigger input. 2. Tektronix Model 7613 Oscilloscope: Featuring two channel inputs, delay time, store and external trigger input. 3. BASS sensor pod, submerged in water 4. Extender board 5. 21 VDC, 1.5 amp Power supply 6. Computer with one RS232 serial port free 7. Onset's TattleTools or other terminal emulation software. 8. BASS Schematics 9. Data Precision Model 3500 4 1/2 digit volt-ohmmeter 10. Onset TC-4 RS232 communications cable 11. Tektronix AM503 Current Probe amplifier with model P6302 probe 12. Oceanographic Instrumentation Systems (OIS) nanosecond delay test unit 13. Capacitance meter

The author has used a number of terminal emulation software packages to communicate with Tattletales rather than the TattleTools software provided by Onset. These procedures, therefore, have been written for use with any terminal emulation software.

Use of trade names is for the purposes of identification only and does not constitute any endorsement by the USGS.

III. Procedures

IV. BASS Transducer and Cable Check

Each sensor pod which makes a three axis current measurement uses a total of eight acoustic transducers to do so. These are generally rugged parts, however their capacitance should be checked periodically and whenever there is any suspicion of damage. To insure that no moisture can penetrate the sealed housing, capacitance should be measured after the transducer has been soaked in water for several days. The capacitance is typically 1000 pf +/- 30 %. Note that the true capacitance will be the capacitance measured with the test leads connected to the transducer minus the capacitance of the test leads by themselves.

The electrical condition of the cables can also be checked by measuring capacitance. Once the capacitance for each transducer has been recorded, the measurement is repeated through the cable. A cable in good condition should not significantly differ from the capacitance reading at the transducer.

V. References

Appendix A. Other Signals of Interest

Appendix B. Suggested Form for Recording Observations

Appendix C. A Tattletale 4 BASS Program

Appendix D. MATLAB Script File for BASS Calibration