plane, and the differential gage reads the 

 deviations of the submersible from that 

 plane. The pressure accumulator was a small 

 high-pressure air bottle. The differential 

 pressure gage was manufactured by Whit- 

 taker Corporation's Pace Wianco Division, as 

 was the pressure transducer (model P7) 

 which operates on a variable reluctance prin- 

 ciple. A demodulator carrier provided the 

 proper input and output voltage condition- 

 ing. The gage system has the following char- 

 acteristics: 



— Input voltage = 22 to 32 VDC 



— Range = 5 feet (= 2.5 psi) 



— Output voltage gradient = 1 volt/foot 



— Linearity = 0.5% best straight line 



— Output impedance = 2 kilohms 



— Resolution. Infinite 



— Volumetric displacement = 3 (lO"**) cu- 

 bic inch. 



A meter readout for this gage was mounted 

 on the pilot's control panel to serve as a 

 navigation aid and to indicate ASHERAH's 

 position relative to the horizontal reference 

 plane. 



Speed Indicators: 



Because a submersible travels in three 

 dimensions, both lateral and vertical speeds 

 are sometimes measured. 



Vertical Speed — Rate of descent is an impor- 

 tant parameter for deep-diving submersibles, 

 mainly because of the danger of hitting the 

 bottom too hard. A knowledge of descent rate 

 allows the operator to adjust ballast or buoy- 

 ancy to slow down (or speed up). Desire for 

 knowledge of the vehicle's ascent rate ap- 

 pears (from conversations with operators) to 

 be essentially for academic reasons. 



The most basic vertical speed indicator 

 was described by A. Piccard (In Balloon and 

 Bathyscaphe) for the bathyscaph FNRS-2. 

 Taking a vane anemometer (identical to that 

 used by balloonists), Piccard mounted it on 

 the top and out to the side of the vehicle's 

 float. The anemometer is a four-bladed fan 

 that rotates in proportion to wind (or water) 

 speed, or the vertical speed of the balloon 

 and in this case was rotated by the vertical 

 motion of the bathyscaph. Because it could 

 not be visually observed, each rotation was 

 electrically signaled through the hull on a 

 different code for ascent and descent. Each 



complete revolution corresponded to a prede- 

 termined distance, and the frequency of the 

 revolutions was observed in the hull as a 

 luminous sparking. 



A second method is used by SEA CLIFF 

 and TURTLE where sequential values from 

 the pressure transducer are differentiated 

 and displayed as a rate of change function. 



A third and most widely used method sim- 

 ply times the rate of descent or ascent 

 through selected depth intervals from the 

 up/down echo sounder trace. The few vehi- 

 cles that have a Doppler Sonar, described 

 later in this section, can also derive rate of 

 ascent/descent from this device. 



By and large, few submersibles measure 

 vertical velocity and, when they do, descent 

 rate is the most important parameter. 



Lateral Speed — Similarly, knowing one's 

 speed across the bottom is of little value to 

 the operator. To the scientist, however, it is a 

 useful factor in reconstructing area observed 

 per unit of time. For example, in biological 

 studies where the number of visible bottom 

 dwelling (benthic) organisms per area tra- 

 versed is desired, speed is critical in deter- 

 mining the distance covered in the absence 

 of other navigation or locating systems. 



There is a wide variety of methods for 

 measuring a vehicle's speed, but the two 

 most generally used are the Savonius Rotor 

 and the Rodometer. 



A Savonius Rotor current meter is shown 

 in Figure 11.4 (Chap. 11). DS-4000 used a 

 similar rotor for speed measurements. As the 

 rotor is turned by water movement, a reed 

 switch is activated to send electric pulses 

 through DS-4000''s hull and to produce a 

 signal on a readout. Each full rotation corre- 

 lates to a given distance through the water 

 which is displayed, generally, in knots. Con- 

 currently, each rotation can be summed to 

 provide distance traveled; in this fashion the 

 rotor acts as an odometer. The obvious prob- 

 lem is: How does one account for speed added 

 or subtracted by water currents? On surface 

 ships the same problem is encountered when 

 measuring wind speed underway, but sur- 

 face ships generally know with fairly good 

 accuracy their speed through the water at 

 various shaft rpm's. Knowing this, calcula- 

 tions for apparent wind speed can be made 

 which ultimately provide true wind speed 



487 



