DESCRIPTION OF INSTRUMENTATION 

 The experimental system was instrumented to measure the following parameters: 



1. body depth below the water surface, 



2. cable tension at the ship, and 



3. towing speed. 



A watertight instrument housing in the depressor body contained electronics for 

 amplification and remote electrical calibration of the body depth sensor. The 

 housing also contained a voltage-controlled oscillator-type telemetry assembly 

 to transmit the depth signal through the towcable to the graphic and digital 

 recorders aboard ship. The cable tension at the ship sensor was direct wired to 

 a control unit within the ship laboratory which contained the tension sensor 

 amplifier and electrical calibration circuit. Ship speed was measured by the 

 DTNSRDC knotmeter. The sensors and their accuracies are listed in Table 2. 



TABLE 2 - MEASUREMENT SENSORS 



Measured 

 Parameter 



Sensor 



Measurement 

 Accuracy 



Type 



Range 



Cable tension 



Dyna-Line 



0-10,000 



+ 200 lb 



at the ship 



tensiometer 



lb 





Body depth 



Diaphragm 

 pressure gage 



0-1125 ft 



+ 5.6 ft 



Ship speed 



DTNSRDC knotmeter 



0-25 kts 



+ 0.01 kt 



The design of the electrical calibration circuits in this measurement system 

 virtually eliminate the effect of long-term zero drift and sensitivity error 

 within the amplifier and recording electronics external to the sensors. As a 

 result the total readout error is limited to that of each individual sensor. 

 These calibration principles are discussed in detail in Reference 5. The ship- 

 board readout electronics consisted of a 6-channel strip chart recorder providing 

 a time history of cable tension at the ship, depth of the body, and ship speed; 

 an integrating digital voltmeter, and two preset electronic counters provided 

 digital displays of the cable tension, body depth, and ship speed, respectively. 

 A digital recorder was used in conjunction with the digital display units to 

 obtain a printed record of the data. 



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