swell, the depth sensor will indicate an increasing depth causing the buoy to pitch nose-up. 

 As the buoy starts to pitch nose-up, the pitch-rate signal will limit or slow the rate of buoy 

 climb. When the buoy has passed the crest of the swell it will start to nose down and its 

 rate of descent will also be slowed down by the pitch-rate signal. Some deviation from the 

 desired 4-foot depth mark will be experienced as a result of the pitch-rate input and deviation 

 will increase as the buoy speed of encounter to the swells increases. However, if the buoy is 

 towed in short-crested waves and no pitch-rate feedback is input into the servo amplifier, the 

 buoy should respond to the leading edge of the wave by rapidly nosing up. After the buoy 

 passes the peak it could not respond to the steep trailing edge of a wave and might broach 

 or pass through the water surface. Buoy broaching at high speed is detrimental to the towing 

 system because of the shock to the buoy and shock loads imparted to the towcable. There- 

 fore, the inclusion of the pitch-rate signal in the servo system should serve as a safety feature 

 to the BIAS buoy operation. 



BUOY OPERATIONS MEASUREMENT SYSTEM 



The Buoy Operations Measurement System was designed to measure only those param- 

 eters necessary for operation of the BIAS buoy during operational deployment from the sub- 

 marine. The parameters are: buoy deep and shallow depth, fine and coarse cable scope, and 

 cable tension. The buoy deep and shallow depth sensors with associated circuitry are mounted 

 in a watertight instrument housing in the buoy. A simplified schematic diagram is presented 

 in Figure 6 and a detailed schematic is shown in DTNSRDC Drawing C-432-5. The shallow 

 depth gage generates a zero to 5-volt d-c output for a depth variation from zero to 50 feet. 

 The deep-depth gage generates a 0- to 5-volt d-c output for a depth variation from to 

 1000 feet. These two voltages are summed at the amplifier and converted to d-c currents of 

 5 milliamps (mA) at zero buoy depth, 7.5 mA for 50-foot buoy depth, and a maximum of 

 10 mA for a buoy depth of 1000 feet. The current signal for depth passes through one lead 

 of the towcable to a grounded lOOO-ohm resistor located in the data center. A second 

 amplifier is provided to null out the 5-volt d-c offset at zero buoy depth and to provide 

 proper drive for the buoy-depth meter readout at the data center. 



A calibration circuit within the buoy is actuated by a pushbutton switch at the data 

 center to monitor and maintain meter readout accuracy. 



SYSTEMS DESCRIPTION 



This section describes the buoy measurement instrumentation, electrical conductors, 

 submarine sensors, recording and auxiliary equipment. Two distinct measurement systems 

 and an automatic buoy depth-keeping servo system which were manufactured under the 



13 



