Scientific Papers of the Bureau of Standards Volume 11 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 edition. Excerpt: ... mean time of these two, ' 2-25-44 is that employed for the mean potentiometer readings in the above. R-Resistance of the S pecimen.--Data pertaining to these measure 'ments are tabulated in the long columns to the right of the record sheet. The readings were taken as described in Chapter V, section 1 (b) (p. 300), and after correcting from the calibration certificate of the potentiometer, they were plotted against time as explained in the same section (p. 301) and served to give the resistances at desired even minutes. These appear in the last column, and are expressed in terms of the resistance of the manganin standard (L & N 7354 at 33.3) and not reduced to international ohms.. In the preperiod the series of values extends to 2-21, so that this value of R, 0.225969, must be employed to determine the value at the desired instant, t, namely 2-22-14, which is 74 seconds later. The computation is given in full in the extreme upper left hand corner of the sheet, and the R, cor is 0.225981, expressed in units which are reduced to international ohms by adding +o.00017, . (The standard resistance was about 0.075 per cent larger than its nominal value, and 0.07 5 per cent of 0.226 is 0.000170.) In the afterperiod, inspection of the values corresponding to the times 2-32 to 2-36, leads to a choice of 0.230107 at 2-32-00 rather than 0.230106 given by the single reading at that time. From this the value of R, 001', corresponding to t, 2-29-14, is obtained, the computations being shown in the lower left corner of Fig. 8. The difference, R'2 cor-R, car, is 0.004154, expressed in the working unit. The resistance of the 0.1 ohm standard was 0.100075 international ohms, 7.5 parts in 10 000 larger than the nominal value, which being 3...