. Report of the Electric Railway Test Commission to the president of the Louisiana Purchase Exposition . employed wassupplied with two shunts, one for a maximum scale readingof 600 amperes and the other for a maximum scale reading of200 amperes. Both of these shunts were used, no currentvalues below 300 amperes being measured, with the 600 ampereshunt. ALTERNATING CURRENT LOSSES 397 Pressure Measurements. — The problem of measuring thepressures was not as easy of solution as that of measuring thecurrents. While the currents involved were large, the pres-sures were very small, being in many cas
. Report of the Electric Railway Test Commission to the president of the Louisiana Purchase Exposition . employed wassupplied with two shunts, one for a maximum scale readingof 600 amperes and the other for a maximum scale reading of200 amperes. Both of these shunts were used, no currentvalues below 300 amperes being measured, with the 600 ampereshunt. ALTERNATING CURRENT LOSSES 397 Pressure Measurements. — The problem of measuring thepressures was not as easy of solution as that of measuring thecurrents. While the currents involved were large, the pres-sures were very small, being in many cases considerably lessthan one volt. When direct current measurements were made,the solution was simple, as accurate Weston instruments de-signed for readings at low pressures were used. On the otherhand, the alternating current measurements were the mostimportant, and yet no accurate alternating current instru-ment for the low pressure was available, the best instrumentobtainable being a standard Weston alternating current volt- Primaries to Multiple K—120 V. Primaries In Series Multiple. 240 Vr. Secondariesin Multiple, Primaries In Series. }« 480 V. s= :••:) <<h V-Secondaries Secondaries in Series Multiple fa Series Fig. 114.—Pressure Transformers Connections for A. C. Tests. meter with a full scale deflection of 7J volts. As this instru-ment would not give accurate readings of the low pressuresinvolved, it was necessary to use a ^step-up pressure trans-former, and one made by the General Electric Company wasaccordingly used. It had four primary and four secondarycoils, the different connection combinations of which are shownin Fig. 114. Ratios of transformation of one to one, one to two,one to four, one to eight, and one to sixteen were obtainablefrom this transformer. All of these combinations were used atvarious stages of the tests. Power Measurements. — Great difficulty was encoimteredin finding a satisfactory method of conducting the measure- 39S ELECTRI
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