Document G1Kq5ZydxXOJEK5ygnJ0rgxx

--V------- /- y \ DIRECTIONS FOR TE9T NO, 14-36-41 SUBJECT: Dielectric Constant of Liquid Aroclor WSTTIOD: Scops This method applies to mineral oils and oil substitute used for insulating purposes. Apparatus Oapacitanoe Bridge General Radio Co.f ^rpe 716-AK Cathode Ray Null Detector Tyne 707-A Oscillator . " " Type 606-A Constant Temperature Oven Cenco-DeKhotinsky #95050 Variable Air Condenser General Radio Co., Type 334-? 1500 co. Ryrex Beaker Procedure Electrode and beaker must be cleaned as directed under "Clean ing Apparatus for Dielectric Constant", end be at 100C. Heat Aroclor in the Can to 105*0. Pour over eleotrode until plates and ceramlo insulation are covered. Connect leads. Stir with thermometer outside oven until temperature reaohes 101; place in oven which has been carefully adjusted to 100C. At the time sam- pie is placed in oven its temperature should not have fallen below 90*0. ' Connect leads to capacitance bridge, observing that the lead front insulated side of condenser goes to insulated terminal on bridge. Balance bridge carefully according to direction under "Balancing Capacitance Bridge". Urttil Aroclor and oven temperatures have beoorns identical the bridge balance will constantly shift. After oven temperature reaches 100C., minta In bridge balance until no pronounced shift is evident. Record reading of capacitance scale multiplied by multiplier setting. Dielectric Constant Capacitance in Aroclor at 100*C, Capacitance in air at 100*C. Balancing Capacitance Bridge -- Condensed procedure. Operator should read operating instruc tion for Null Detector for complete details. 1. Connect to power supply leads to oscillator and null detec tor. Ground the oscillator. , 2. Turn on oscillator by pushing 5000 ohm, 10 multiplier, 100 cycly frequency buttons. Adjust harmonic control until oscillation begins as shown by olosing of sector in oathode ray tube. . dS>N 330897 STLCOPCB4077541 Page #2 Dielectric Constant of Liquid Aroolor - Test 14-36-41 \ 3, On null detector turn brilliance knob to extreme left, the focus knob to extreme right, gain control to extreme left, steep amplitude 8t raid-scale position, the sweep frequency switch on line side. 4. Turn on power switch, lighting pilot light. 6. Wait fifteen seconds, turn brilliance knob to extreme right. 6. Adjust focus and brilliance knobs until sharp fine line. 7. Conneot external terminals on detector to output terminals on oscillator. Switch sweep frequency to external side. 8. Conneot detector terminals of bridge to input terminals of deteotor, taking eare that the blaok wire (ground wire) of the lead goes to grounded terminal on both ends of lead. 9. Set gain control at mid-scale and selectivity to extreme left. Turn sweep amplitude to extreme left. Obtaining vertical line. With t' - 10, With turning control knob obtain the maximum length of this line, keeping it always under 1/4 inch with gain knob. 11. Set sweep amplitude to extreme left. IE. Set gain control to give vertical straight line of about 3/8 f inch. .. 13. Balance bridge by adjusting power factor and capacitance diale until Only a dot remains on the screen vfaen the gain control is at extreme right. 14. Set sweep amplitude beyond mid-point, and slightly displace the power-factor dial to obtaiq a tilted elipse. ; '' r . . ' . 15. Adjust phase control until this ellipse closes into a straight line inclined to the horizontal. ; f 16. Bring power-factor dial back to balance position, which should restore the horizontal strai^it line. Displace this control the same amount in the opposite direction. This shoulA again tilt the straight line but in the opposite direction. juslf phase, oontrol until there is no tendency for this line to open up when it is' swung 30 degrees from horizontal in both directions. 17. Throughout these adjustments the other bridge oontrol (the DSW 330898 STLCOPCB4077542 Page #3 . Dielectric Constant of Liquid Aroclor - Test 14-36-41 capacitance Dial) must be in balanoe position. If the ellipse grad ually opens when the line is horizontal it nay be brought back to the line again by making slight changes in this control. If confusion results, balance both controls again as In (13) and repeat the suc ceeding adjustments. . This is the position of bridge balance: An alteration of the power-factor control will tilt the line which does not open apprecia ble thru an angle of 30* to the horizontal both ways; an alteration of the capacitance dial opens the ellipse but does not change the inclination of the major axis. The apparatus may be left in this balanced condition, turned off by switching off first the brilliance knob of the detector, then the power switch, then turning off the oscillator. - For successive measurements the controls are not changed, the apparatus left in adjustment. Then the following steps define the procedure: 1. Connect all leads as previously directed including that from null detector to bridge, 2. Turn on oscillator by pushing 100 cycle frequency button, 3. Turn on null detector, wait 15 seconds then turn on cathode ray tube. Turn sweep amplitude to extreme left and adjust brilliance to Obtain a fine vertical line on screen. 4. Bring this line to a dot by adjusting the two bridge controls. Initial adjustment is facilitated by having "Gain" control to left. When final adjustment is obt^ine^ this knob,must be at extreme right, 5. This dot reneining unchanged shows' Condition of bridge balanoe. Cleaning Apparatus for Dielectric Constant The condenser is removed from the tested dielectric and allowed to drain while still in the oven at 100CC. The condenser is then placed, while still hot, in a beaker of benzene under a -well ventilated hood and allowed to cool. It Is then thoroughly washed with powdered tri sodium phosphate and a 50-50 mixture of benzene and carbon tetrachloride followed 'by an acetone rinse. Th operator should be/ very careful not to touch the metal plates of the condenser .after this point. The condenser is then rinsed thoroughly with tap water followed by distilled water and dried on a clean paper in an oven at 120*C for at Ipast one hour or until it is again used. . swb 3/1/48 DSW 330899 STLCOPCB4077543