Electrical measurements

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 Excerpt: ...has shown that with careful construction the pressure may not fall more than 20 lb. during a year from an initial value of 220 lb. per square inch. Compressed gas condensers are used in connection with radiotelegraphic apparatus. Fig. 209 shows one of those installed at Arlington, Va., by the United States Government. Working Standards of Capacity.--Though the determination of the capacity and phase angle of working standards of capa Microfarads B Fig. 210.--Subdivided condenser. city depends ultimately upon the use of secondary air condensers, such instruments are not suitable for general use in the laboratory on account of their size, and more convenient arrangements must be employed. Ordinarily the capacity of laboratory standards is of the order of magnitude 1 microfarad. Such standards should be subdivided and made adjustable by arrangements for placing the various sections in parallel. When this is done the net capacity in terms of the capacities of the various sections is C = Ci + c, + c, +.... The usual construction of the terminal blocks for putting the, sections in parallel is shown in Fig. 21Q. By the proper insertion of the plugs, the sections may be put in parallel as desired, any section may be discharged, or the whole condenser may be short-circuited. For precision standards of small capacity, this scheme of connections is open to the objection that the capacity of the top itself, which depends upon the position of the plugs, is included between the terminals. For precision work, it is better to have each section provided with small and well-insulated terminal posts, spaced as far apart as practicable. This also allows the sections to be connected in series as well as in parallel. With the series connection the capacity will be The capacity i...