BUOY EVALUATION MEASUREMENT SYSTEM 



This system is designed for accurate measurement of buoy and towcable parameters 

 while the buoy system is towed for evaluation purposes. A simplified block diagram of this 

 system and a partial schematic of buoy instrumentation (showing only one typical sensor 

 channel) are presented in Figures 2 and 3, and a detailed schematic is shown on DTNSRDC 

 Drawing C^32-2. Within the buoy there are four potentiometer-type sensors, each of which 

 generates a 0- to 5-volt d-c output as a function of the physical parameter being sensed. 

 These parameters include buoy pitch, buoy horizontal stabilizer angle, buoy deep depth, and 

 buoy shallow depth. In addition, there are two leak detectors which generate electrical pulses 

 only if leakage occurs within the watertight compartments. The leak-detector outputs are 

 coupled with the pitch and deep depth signals and appear as momentary blips atop the 

 recorded parameters. In conjunction with each sensor there is an electrical calibration net- 

 work with three voltage taps. A rotary-solenoid switch is used to make electrical contact 

 with these taps and the sensor output. To complete a calibration sequence, the stepping 

 switch is rotated through four switch positions entitled; Zero Check, Cal 1, Cal 2, and Data, 

 the Zero Check position corresponds to a physical-sensor zero; Cal 1 represents a discrete 

 physical-sensor displacement; Cal 2 represents a second but different displacement than Cal 1: 

 and finally the Data position corresponds to the direct output of the sensor. 



The rotary solenoid is energized and the switches are automatically sequenced through 

 the four positions by a silicone-controlled rectifier and an oscillator network. The switching 

 sequence is initiated by depressing a pushbutton switch in the data center, which causes an 

 electrical impulse to travel up the towcable to the calibration sequencing network. 



Commercially available voltage-controlled oscillators (VCO's) of the Inter-Range Instru- 

 mentation Group (IRIG) frequency assignments are used in this system for combining the 

 four sensor outputs into one composite signal for single-conductor transmission down the 

 towcable. The d-c voltage output (or cal signal) of each sensor is connected to a VCO. Each 

 VCO converts the d-c input signal to an a-c frequency wherein the frequency deviation from a 

 center frequency is proportional to the variation of the d-c voltage input. The center fre- 

 quency of each VCO is different from the next such that if all the VCO frequency outputs 

 are mixed there will be no overlapping or interfering frequencies. The four VCO outputs are 

 mixed and input to a low impedance line driver for transmission down the towcable. 



Within the data center the telemetry signal is unscrambled by a four channel frequency 

 modulated (FM) discriminator. This instrument sorts out the four frequency bands and con- 

 verts each frequency band to a d-c voltage proportional to the sensor output. The four 

 discriminator outputs then are connected to the input of a multichannel strip-chart recorder 

 which produces a time-history trace of each of the physical inputs to the buoy sensors. 



