The effect of power factor on the accuracy of integrating wattmeters
An engineering thesis on electric meter accuracy submitted by Percy Belmont Bradshaw and Horace Gaylord Hobbs at the University of Illinois in 1908, written for examiners and electrical engineers. The plates are hand-inked test curves plotted on orange gridded graph paper, with circled data points and lettered axes labelled for percent error and load — usable as ready-made technical line work and grid textures.
