BUOY OPERATIONS MEASUREMENT SYSTEM 



A second measurement system, which was designed as a permanent part of the BIAS 

 buoy system, is used during submarine patrols. This system utilizes several of the aforemen- 

 tioned shipboard sensors, but requires different buoy instrumentation consisting of a shallow- 

 depth gage (0 to 50 feet) with a blanking valve attached to the pressure orifice to protect 

 from overpressure; a deep-depth gage (0 to 1000 feet); a pressure sensitive switch which is 

 closed between to 10 feet of depth; electronics to sum the shallow- and deep-depth signals; 

 and a watertight instrument housing to contain the above items. The instrument housing 

 is electrically connected to the submarine buoy control center via two leads and a shared 

 ground lead of the towcable. A power supply, signal-conditioning electronics, and a meter 

 are provided aboard the submarine for depth readout. A pressure-sensitive switch is provided 

 as one of several inputs to the logic circuitry for buoy destruction. 



The accuracy of this system, assuming a worst case condition over a range of a 20-degree- 

 Fahrenheit temperature change, is determined to be approximately 5 percent of full scale. A 

 3-percent error is attributed to the sensor, largely due to temperature variation, a 0.5-percent 

 error is attributed to the meter driving electronics, and a 1 .5-percent error is due to the non- 

 linearity and friction within the meter readout unit. 



BUOY EVALUATION MEASUREMENT SYSTEM ACCURACY 



The accuracy of recorded buoy data obtainable from the evaluation measurement system 

 is essentially limited only by the accuracy of the sensor, the resolution of the readout device, 

 and the requirement of short term zero and sensitivity stability of the telemetry and record- 

 ing electronics. In general, the accuracy of the potentiometric-type sensors used in this system 

 is primarily affected by the systematic errors caused from environmental temperature variations 

 and the electro-mechanical nonlinearity inherent to each sensor. A temperature change effects 

 both an electrical resistance change and mechanical dimensional change to the linkage within 

 the sensor. Temperature changes affecting the electrical resistance of the sensors do not affect 

 the accuracy of the final data because of the calibration networks designed for use in this 

 system. Each network is comprised of precision resistors connected in series and the total 

 network connected in parallel with the sensor. Each junction between the resistors of the 

 network represents a discrete position of the potentiometer arm and this relationship is inde- 

 pendent of temperature because the resistance of the potentiometer changes uniformly through- 

 out the resistance element. The errors caused by dimensional changes due to temperature 

 (particularly in the depth sensors which contain more complicated linkages) do affect final 

 data accuracy. 



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