An improved electrothermic instrument

Discussion and author´s closure of a paper by P. M. Lincoln, published in the May 1935 issue, pages 474–81, and presented for oral discussion at the instruments and measurements session at the summer convention, Ithaca, N. Y., June 25, 1935. True McLean (Cornell Univ., Ithaca, N. Y.): In his paper on “Rates and Rate Making” written in 1915, Prof. P. M. Lincoln showed that the instrument shown schematically in improved form in figure 6 of the present article is a true wattmeter. In the present article he has described improvements in the thermal and mechanical systems so that errors due to thermal and mechanical causes can be reduced to very small percentages. In all previous instruments of this general type, the errors were relatively so large that a rather crude electrical system was so much better than the rest of the apparatus, that refinements of the electrical system were a total waste of effort.