CENTIMETERS 

 I 2 3 



Figure 1. — A typical irradiance meter detector housing: A, cosine collector; B, clear plastic window; C, threaded brass 

 cap; D, brass photovoltaic housing — base section; E, optical filter; F, O-ring; G, photovoltaic cell; H, Joy plug; 

 J, supporting arm; L, locking screw for supporting arm; M, pressure plates; N, screws for pressure plate. 



below the photovoltaic cell (G), prevents pos- 

 sible internal window fogging and internal 

 moisture damage to gelatin-type filters re- 

 sulting from condensation of water vapor con- 

 tained in the detector unit. The two con- 

 ductors of the Joy plug (H) (Joy Manufacturing 

 Co., Compton, Calif.) are connected to the 

 photovoltaic cell terminals. A watertight seal 

 is effected between the housing (D) and the Joy 

 plug (H) by tightening the screws (N) of the 

 pressure plate (M) and thus compressing the 

 external rubber collar of the Joy plug. A 

 recessed shoulder on the bottom of the clear 

 plastic window (B) holds the filter in place. 

 The cosine or Lambert collector (A) is placed 

 above the window and may be fused to it by 

 use of a suitable solvent. The collector (A) is 

 so machined that 1 to 2 mm. protrude above 

 the threaded cap (C) when the cap is tightened. 

 The watertight seal is obtained by tightening 

 the cap with enough force to effect a seal be- 

 tween the silicone -lubricated O-ring (F) and 

 the window (B). One or more holes are drilled 

 part way into the housing (D) to accommodate 

 one or more supporting arms (J) whichmaybe 

 locked into position with set screws (L.). 



The cosine collector (fig. 1) was fabricated 

 from translucent plastic (Plexiglass No. 2333, 

 Rohm and Hass, Philadelphia, Pa.), the ex- 

 ternal surface of which had been abraded with 

 No. 180 grit carborundum. No laboratory tests 

 of the collecting properties of this plate were 

 made. The design paralleled that of Foster 

 (1951), who used pot opal glass rather than 



plastic for the collector. Foster found that 

 elevating the surface of the collector above 

 the instrument housing permitted flux to pass 

 through the edge of the collector; this arrange- 

 ment helped to compensate for the losses due 

 to specular reflection at low angles of inci- 

 dence. Since little of the downwelling flux 

 reaching a horizontal plate suspended in the 

 sea strikes at low angles, this design is be- 

 lieved to provide adequate data for biological 

 studies. 



Hermetically sealed barrier layer cells, the 

 self-generating dry-disk type (Model 856RR) 

 manufactured under the name Photoronic 

 Photoelectric Cell by the Weston Electrical 

 Instrument Corp., Newark, N.J., have been 

 used as the radiant flux detectors. These 

 photovoltaic cells have proved stable and suf- 

 ficiently rugged for use in this application. 



The signal generated by the photovoltaic cell 

 was conducted to the vessel by a two-conductor 

 (steel wire. No. 18 gage) neoprene-covered 

 cable, which also supported the underwater 

 components of the irradiance meter. Water- 

 proof connections between the support cable 

 and the underwater components of the meter 

 were made with matching polarized Joy con- 

 nectors (fig. 1, H). This configuration made it 

 possible to detach and store the underwater 

 unit in a protected location on shipboard be- 

 tween lowerings. 



The support cable was handled from either a 

 hand-operated or motor-driven winch. During 

 a measurement series, the cable passed over 



