Bowin 



A stable and reliable power supply is essential to a system. 

 Inverters with precision frequency control were purchased for the 

 R/V chain to supply power to the computer. These inverters have 

 several advantages. They provide a precise and stable frequency 

 for the operation of the system. The IBM 1710 computer required 

 a primary power frequency stability of ± 0. 5 hz, which could not be 

 met by normal ship's power. Precise frequency is also important 

 for all clocks and recorders that have synchronous motors as their 

 basic driving motor. The inverters were modified so as to be 

 driven by an external oscillator, which, in our case, provided 

 frequency control that was accurate to better than one thousandths 

 of a hertz. In addition, the inverters were powered by the ship's 

 DC battery which in turn is trickle-charged by the ship's DC buss. 

 This arrangement assures continued operation during possible 

 ship's power failures lasting up to forty-five minutes. Another 

 advantage in operating the inverters from a battery is that large 

 voltage transients on the ship's DC buss are in large part filtered 

 by the battery before they reach the inverters. Our system utilized 

 one 3 KVA inverter and one 10 KVA inverter. 



An important aspect of a real-time computer system is the 

 identification of the data which is collected. We chose to identify 

 the data by the date and time at which it was sampled. That 

 identification might prove to be a troublesome source of difficulty 

 was in large part only recognized during subsequent data analysis. 

 Errors that occurred included failures of the contacts in the 

 mechanical clock, thereby resulting in invalid or erroneous values 

 being supplied to the computer. Errors also occurred because the 

 clock stopped whenever the computer power was turned off. 

 Oftentimes during initialization of the program, the operator either 

 would forget to enter the date and time or would enter erroneous 

 values. In all these cases the errors proved very troublesome in 

 processing the data later on shore. In the new system, we are 

 endeavoring to eliminate these problems. To this end we have 

 obtained a solid state electronic calendar clock that operates 

 independently of the computer, and supplies the system with the 

 day and month, and time in hours, minutes and seconds. This 

 clock will also have its own battery backup supply in case of ; 



failure in the inverters. Whenever the system requires the time 

 and date, it reads the clock, thereby always having accurate and 

 reliable time. We expect this to be far superior to manually 

 setting the time, and utilizing a counter within the computer 

 program. 



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