ARRANGEMENT OF EQUIPMENT 



The control panel (figs. 1 and 8) contains switches 

 that actuate main power; tank illumination; thermostat; 

 pump; lid elevation and lowering; indexing and reversing 

 operations; and forward and rear stirrers. The panel is 

 located on the right, front, tank- supporting leg and can be 

 swung in a 270-degree arc to position it in the most conve- 

 nient location for use at the control console or at the telescope. 



An elapsed-time meter is installed on the control 

 panel and electrically wired to one of the stirring motors. 

 The ON time of the motor is more representative of actual 

 calibration time than any of the other electrical components, 

 and the meter is used to keep a record of the calibration 

 times. The data are consulted for future work scheduling, 

 to ensure completion of calibrations in time for ship sailing 

 dates and other deadlines. In addition the data serve as a 

 reminder of routine tank servicing needs, such as lubrica- 

 tion of motors, gears and linkages, and filter cartridge 

 changes. 



FILTER 



A full-flow filter (fig. 5) is installed between the 

 main tank return outlet and the thermal system. Ball valves 

 are mounted at the two orifices of the filter and a pipe with 

 another ball valve bypasses the assembly. With the ball 

 valves closed and bypass open, the filter cartridges can be 

 changed without halting tank operation. As the main tank 

 nears its lower temperature limit, the cooling rate de- 

 creases due to the limitations of the refrigeration system. 

 The filter bypass can then be opened to allow faster and 

 larger flow across the refrigeration coils. 



TEMPERATURE STANDARD 



A Leeds and Northrup platinum resistance ther- 

 mometer (fig. 4b) and an associated Mueller bridge Type G-2 



