by Electro-Instruments, Inc. An input scanner, 

 with a maximum switching speed of 50 channels per 

 second, selects sequentially 26 temperature out- 

 puts, one pressure output, 3 calibration outputs 

 and 2 time signals. The signals are amplified 

 in a DC amplifier of adequate bandwidth. The 

 analog to digital conversion is accomplished by 

 means of a digital voltmeter with a maximum con- 

 version rate of 1,000 readings per second. The 

 time base for logging is a digital clock. The 

 logging control allows for selection of scan 

 cycles with intervals of from one second to 30 

 minutes (also continuous). Recording is by means 

 of a printed tape recorder and /or a tape punch. 



With the current set of thermistors, the log- 

 ging rate is normally set at 10 seconds. In this 

 mode both the tape punch and the printed tape 

 recorder are used at all times in recording data. 



By cutting the printed recorder out of the system 

 and using only the tape punch, the sampling rate 

 may be increased from 3 to h channels per second 

 to 9 to 10 channels per second. With a faster 

 tape punch the sampling rate may be increased to 

 approximately 17 channels per second and addi- 

 tional changes can be made for further increases. 



OVERALL ACCURACY AMD PRECISION 



The accuracy of the temperature measurement 

 depends on the accuracy of the calibration, 

 linearity of the bridges and the accuracy of the 

 digital system. The maximum error is +0.005°C. 

 The overall precision of the temperature measure- 

 ments, using probable error as the criterion, is 

 the square root of the sum of the squares of the 

 precision of the calibration and of the precision 

 of recording which has been evaluated at to. 003£Pc 

 The accuracy and precision of the depth indicating 

 system are not well known but are probably a small 

 fraction of a foot. 



REFERENCES 



1. UFF0RD, C. W., Internal waves in the ocean, 

 Amer. Geophys. Union Trans ., 28 , 79-86, 

 February 194-7. 



Fig. k. Visual monitor and recording system. 



UFF0RD, C. W., Internal waves measured at 

 three stations, Amer . Geophys . Union Trans . , 

 28) 87-95) February I9V7. 



RICHARDSON, W. S. and C. J. HUBBARD, The con- 

 touring temperature recorder, Deep - Sea Res . , 

 6, 239-2W, i960. ~ 



■ OPERATION 

 PEN, CONTACT 

 CLOSURE 

 FOR STRIP 

 CHART RECORDERS 



Fig. 5- Digital data recording system. 



52 



