"C" BATTERY MODIFICATION FOR SPECTROPHOTOMETER 
"C" BATTERY UNIT 
| SCREEN VOLTAGE ADJ. 
| (CENTRALAB PA 200!) 
TEST SELECTOR SWITCH 
(CENTRALAB PA 2005) 
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| PUSHBUTTON SWITCH 
POLARITY SWITCH 
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[RAEUEIS TEST KIT 
Figure 4.--Diagram of wiring in ‘‘C** battery unit and meter test unit. (Terminal strip positions B and C are connected to 
the yellow and white leads in the Beckman DU Spectrophotometer, respectively.) 
meter which shows the rate of charge 
of the batteries. In addition, the oper- 
ator may select from this unit the bat- 
tery which will be used during the 
operation of the instrument. 
The ''A' batteries are contained 
in a separate box and may be placed 
in some convenient or remote location. 
Connection between the storage battery 
box and charger unit is made by a six- 
conductor ''extension'' cord equipped 
with polarized amphenol or similar 
connectors. These connectors (also 
used elsewhere in the modified in- 
strument) have given excellent service 
and have shown no tendency to corrode 
under these conditions. 
Figure 5 shows the wiring diagram 
for the battery charger unit. 
Due to a vessel's motion the level 
of the electrolyte in the '"'A'' batteries 
(i.e., 6-volt storage batteries) must 
be kept at a high level or an unstable 
dark current will result. Mounting 
these batteries athwartships also helps 
stabilize the dark current for the same 
reason. Also, best results have been 
obtained by soldering the 6-volt, 2- 
volt, and negative leads directly to the 
battery. 
Modification of Cell Holder 
One spectrophotometer is used 
solely for the measurement of phyto- 
plankton pigments. In tropical waters 
this requires the use of a 10-cm. path 
length and an absorption cell of rela- 
tively small volume (i.e., ca. 5-6 ml.) 
