Document 3e63vkYzZJ7v72p09agy0pbGJ

PROCEDURE FOR DIELECTRIC TESTING OF LIQUIDS FOR 60-CYCLE POWER PACT ON TYPE 716-A BRIDGE Special Equipment: (1) 25-ml Balsbaugh cell. (2) General Radio Type 1213-B null detector with 60-cycle filter. (3) Step-down transformer (to 55 volts) with 5,000 ohms in series with out put, for 60 cycle source. This should he located as far as possible from the null detector. (4) 1,000 /*'/*' f condenser (of power factor 0.25-0.30$ at 60 cycles), plugged' irxto the "UNKNOWN" terminals. This is the balancing condenser. (5) Coaxial cable from the Balsbaugh cell to the "PARALLEL" terminals of the . bridge. Procedure: (1) The cell is filled to cover the electrodes, placed in the oven and the leads attached. (It may be warmed with a burner before placing in the oven, to speed the attainment of temperature equilibrium.) It should not be left in' the oven more than 1 hour before measurement. (2) The bridge is balanced, and the capacitance and dissipation factor dial readings recorded as "C" and "D" respectively. (3) The "hot" lead is disconnected from the cell, and the bridge balanced again. The readings "C" and "D" (the lead-blank values) should be larger than "C" and "D". (4) The coaxial leads are disconnected from the "PARALLEL" terminals, and the bridge balanced again. The reading of the capacitance dial is recorded as "0^". (This value should be a constant for a particular balancing condenser, and needs to be checked only occasionally.) (5) Calculation: Let C and D be values obtained with cell connected. Let C' and D' be lead-blank values. Let 0^ - capacitance of balancing condenser. C^ - capacitance of internal leads of cell. Cft * capacitance of cell with air diolectric. DS\N 331108 STLCOPCB4077752 --2 -- Ca and Cfl are constants of the cell, and will be furnished by the Research Laboratory. C'-C-Cfl - Cx capacitance of cell with unknown dielectric. D' -D AD Cb * ................ . AD --' -- Dx, the dissipation factor of the unknown dielectric. Cx fo x T" Dl. of the unknown dieloctric. Ca Where f - 60 cycles - the frequency of the applied voltage fo 1000 cycles the frequency at which the bridge is set. (5) Example: (Aroclor 1242 at room temperature) C' St 967.2 D' - 4.61 c ' m 817.6 D - 0.91 Cd m 3.8 AD - 3.70 Cx K 145.6 Cb m U10 .8 Dx m 3.70 X 1110.8 T 145.8 60 1000 - 1.69# Reference: "Operating Instructions for Type 716-A Capacitance Bridge" General Radio Company. rs 9-1-50 R. J. Good August 29, 1950 DSW 331109 STLCOPCB4077753