Document N2bEdpX88x4ZXmpx9v17Lr3ED

Date: l/lo/57 By: CM:GWM Material; Aroclors, Pyranols . and Inerteens Test: Resistivity Meth od Me . 11 .07-^7 i W.Q.K. Dent, Tin, ' ' ` Page; 1 fof "6 oag (# to introduction Consult Method No. 11,752 for the sequence of electrical measurements and the terms used in connection with the determination. The Resistivity of an electrical insulating oil is an index of its in sulating properties. High resistivity indicates high resistance to the passage of electrical current and normally, but not necessarily, establishes the absence of conducting contaminants . SAFETY In as much as measurements muet be made at 3 potential of 500 voi.'::; ' ; a shock hazard exists in the handling of this apparatus. With the control knob in the charge anc operate position*-full voltage of the bridge (500 volts) is applied to the + and low terminals and thro the test leads to the electrodes. Do not attempt to handle the o'i-.-ctrodes or the test leads unless the control knob is in the :5C'I3CK1 2 3 4 5 6 7 position. Possible_pena 11v__fcr .failure_to observe this precaatlon - PROCEDURE 1. Assemble the test cell. Place the recently cleaned (within the last S hours--see Method No. 11,751, Step 9) electrodes in an Date: l/lo/57 By: CM:GWM Material; Aroclors, Pyranols and Inerteens Test; Resistivity Method No. 11,607-57 , W .0 .K. Dept. No, 246/233 Page; 2 (of 6 pages) 8oo-ml, beaker. . 2. Measure the capacitance of the test cell (K) according to Method No. ll,6o8 (Dielectric Constant and Power Factor measurements). 3. Fill the cell assembly until the liquid level is j/4 inch above the top of the electrodes . . 4. Heat the assembly oh the hot plate to 100 (+ 0.5)C. 5. Place the assembly inside of the testing oven. 6. Connect the back wire inside the oven to the lead on the outer cylinder of the cell and the front wire to the lead on the inner cylinder of theicellgi 7. Connect the coxial cable from the megohm bridge to the fitting:on top of the oven. NOTE; Check to see that the other end of the coxial cable is con nected to the set of terminal at the right on the- megohm bridge so that the red part of the plug is inserted into the terminal marked "+".. [' i DSW 551071 STLCOPCB4089488 Date; 1/10/57 By: CM:GUM MaterialArodors, Pyranola and Inerteena Teat: Resistivity Method No. 11,607-57 W.Q.K. Dept. Wo. 246/233 Page: 3 (of 6 pages) 8. Throw the three switches at the top of the megohm bridge to "ON" position. 9. Allow 10 minutes for assembly to reach temperature equilibrium inside the oven. . . CAUTION: Make sure control knob on the megohm bridge is in "3L7;0K" position while making electrical connections. Ctharwlse painful shock wlfrl-.yeaThere ia a potential of 500 volts across the terminals used, in this test. - 10. Bring the galvanometer pointer to zero by turning the "".Erie ADJUST" knob in the direction in which the pointer' of.the gal vanometer should move. 11. Turn the control knob to "CHARGE" position for 30 seconds. (Use stopwatch) ' 12. Turn the control knob to "OPERATE" position and return the gal vanometer pointer to zero by adjustment of the "MULTIPLY BY" switch and the megohm dial. 13. Read after 30 seconds. (Time the 30 seconds by stopwatch from the time the control knob was turned to "OPERATE".) Date: 1/10/57 Bj: CM:GWM Material: Aroclors, Pyranola and Inerteens Test: Reslfttivity Method No. 11,607-57 W.Q.K. Dept: No. 246/233 Page: 4 (of 6 pages) CALCULATION Resistivity* Megohm dial reading (Step 12) x "Multiply By" reading (Step 12) x capacitance of cell (K value, step 2) in uuf. x-11.29 x 0.00? Report the result in units of IQ9 ohra-cm. * Values of resistivity are qualified by designation of temperature and voltage* These are for this test, 1QQC. and 500 volts DC. NOTE: It i important that the product under test, electrodes, and beaker be at uniform temperature for this determination. Temperalajre variations in different-parts of the sample will cause Jfche galvanometer zero to change constantly and give misleading results. " AEP&Rfflg general Radio Co. Megohm Bridge Type- 544-R,. This ^^combination of Wheatstone bridge and vacuum tube voltmeter' fbr-Indicating null. The dlrect measureoent o^ resistance^ up to 1,000*DOCKdfigobas is made possible by the uam^ of vacuum tube detector whichfrabsorbe negligible amount^otfpower. DSW 551072 STLCOPCB4089489 ^ate: l/lo/5T By: CM:GWM Material: Aroclors, PyranoXs and Inerteens Teat: Resistivity Method no. 11 O'" -57 Page.: 5 (of 6 pages) The voita53 applied to the unknown resistor is held approximately con stant, regardless of the value of the unknown resistance. This con dition is necessary to measure resistance properly, .' The accuracy of the instrument in the range encountered in she uoucore- i.*.2nt of Arcelor resistivity, ICO to 1CCC megohm is 6/. The instrument is equipped with a 115 vein Ah pov-er supply which supplies all operating voltage3 for the bridge indicating c ireu:/;s and in addition supplies 500 V 310 for application to the material under tea t. The instrument in completely enclosed in a waxed finish shielded :ii . cabinet measuring S-l/2!i wide. 22 -l/2 " long and 3:I high. Approximate weight--26 pounds. TEST ELECTRODES Two concentric nickel cylinders with feet, detained from General Elo ::;rU' Co. The inner electrode has outside diameter of 2,8s* and a hsi th-i -?f 5,25" with, area of 184 sq. cm. The outer electx'cde has inside die.nor-er of 5M and height of 3.25" with area of 193 sq. cm. The distance between electrodes is therefore 0.1" or 0.254 cm. Date: l/lo/57 By: CM:GWM Material: Aroclors, Pyranois and Inerteena Test: Resisfivlty Method .Np^ 11,507-57 ; ,a ,K, Pact, ho. ft.5.'03; Page: 6 (of 6 pages) By theory, electrode constant (X) area/length is 191/0,254 or 752 where average area is 191 sq. cm. Also X = 36'Tfx 1011 x C (in it.rads with air as dielectric) 11/29 v 0 (in-uuf, with air as dielectric). ` > ' ' GLASS PLATE Pyrex about 3-1/2" diameter with concentric grooves to assist In spacing electrodes. Obtain from General Electric Co. TktiM.su~.dc------ '6; .V".: . : \:---r.ditton* or suffir'iens art mdt viibouk (unotot, sact tbt eonoiuuu c( list artbtyoiMi our control kMuatBditctfm tajr (iattUty far Wm tr Mil Itaartk It cifidiot tttkikt auaf UMtfctm, 0S>N 55^073 STLCOPCB4089490