Three recorders have been employed with the IT-1. These are: 



(1) Bausch and Lomb Model V. O. M. 5 



(2) Sargent Model (SR) S-72180 



(3) Nesco Model JYllO 



If size and weight are not to be considered, the Sargent is preferable to the B&L be- 

 cause of greater accuracy (l/4°/oo vs. l/2°/oo), wider chart (10 inches vs. 5 inches), noise 

 filter controls, and a range attenuation feature that is especially useful in recording IRT 

 measurements. The greater bulk and weight of the Sargent (45 lb vs. 16 lb.), however, 

 make it difficult to transport and mount in an aircraft. The B&L V. O. M. 5 is considered 

 a relatively accurate and dependable recorder for IRT work. The Nesco instrument has 

 been less promising than the other recorders in Institute operations. 



Power sources vary with usage. During tests on the York River bridge, housepower 

 was used for the IRT and strip-chart recorder. On ships and during bay surveys in the 

 Cessna, two 12-volt storage batteries connected in series are utilized to run the IRT and 

 recorder. An inverter converts the DC battery output to about 128 volts AC. A variable 

 rheostat and on-line voltmeter permit a regulated power supply of 115 v. AC. A meter 

 monitors frequency. A spare inverter is carried on flights as it is recommended by the 

 manufacturer that these units not be used continuously for more than five hour periods. 



On shelf flights 28 -volt plane power (supplied directly to the inverter) is used in- 

 stead of batteries. 



The biggest single problem encountered with power supplies is the frequency vari- 

 ability when using batteries or a 28-volt generator with an inexpensive inverter. A sharply 

 defined frequency is rarely obtained. The frequency is normally about 62 cycles per second 

 and this may vary as much as 2 cps over a short period, although in general the peak re- 

 mains at ± one cycle. The effect of this on accuracy of readii^s and recordings has not 

 been defined with certainty, but no large discrepancies were noted during limited laboratory 

 tests . 



It has been found that new well-charged batteries serve as an adequate power source 

 for continuous IRT and recorder operating periods of longer than 10 hours, but no enduranct 

 trials have been run to specifically test maximum life expectancy. 



The following is a list of power supply components used in VIMS operations: 



BATTERIES (2) — 12-volt heavy duty automotive storage 



INVERTER - ATR DC -AC, type 28U model RSF, input 28 volt 

 DC (recommended, however, for 24 v systems), 

 output wattage int. 125, cont. 100, AC output vari- 

 able by four steps. 



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