1、l Designation:D 3114-72(Reapproved1982)An American National Standard Standard Test Method for D-C ELECTRICAL CONDUCTIVITY OF HYDROCARBON FUELS This standard is issued under the fixed designation D 3114;the number immediately following the designation indicates the year of original adoption or,in the
2、 case of revision,the year oflast revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope l.l This method applies lo the laboratory determination of the rest electrical conduc-tivity of
3、aviation fuels and other similarly low-conductivity liquids in the range from 1000 to O.Ql pS/m(see 4.2).With suitable battery op-erated components,the method can be used in the field.2.Summary of Method 2.1 A sample of fuel is placed in the conduc-tivity cell which is then connected in series with
4、a d-c voltage source and a sensitive d-c am-meter.The conductivity is calculated by Ohms law from the cell characteristics,the voltage across the cell,and the almost instantaneous peak current reading.3.Significance 3.l The generation and dissipation of elec-trical charge in fuel depend largely on t
5、he ionic species present which may be characterized by the rest electrical conductivity.4.Definitions 4.1 rest conductivity-the conductivity of uncharged fuel in the absence of ionic depletion or polarization.It is,in effect,the conductivity at the initial instant of a d-c measurement.4.2 picomho/me
6、ter-an arbitrary unit of electrical conductivity,also often called a Con-ductivity Unit(C.U.).In the SI,picosiemens replaces picomho.I C.U.=I picomho/m=1 x 10-120-im-1=I pS/m 23 5.Apparatus 5.l Components of the conductivity test ap-paratus are shown in Fig.1 and the assembled apparatus in Fig.2.5.2
7、 Conductivity Cell,consisting of a TFE-fluorocarbon insulated,two-terminal electrode assembly,and a sample holder so configured that the electrodes are suspended in the sample without the sample contacting the insulation.The electrode gap should be not less than l.O mm,and the cell constant should b
8、e not greater than 0.01 cm-1 5.2.1 A typical cell assembly consists of(a)an electrode assembly,(b,a 250-ml stainless steel Griffm-form beaker and(c)a stainless steel or aluminum support disk about I mm thick and 80 mm in outside diameter with a 32-mm diameter center hole.Three equally spaced tabs be
9、nt down from the rim will keep the disk centered on the beaker.5.3 Sensitive d-c Ammeter,capable of mea-suring to a least significant increment of 3 X 10-14 A,with an error not exceeding 5 percent of the full-scale meter deflection,and with a rise time(10 to 90 percent)of less than 2 s for currents
10、greater than 3 x 10-13 A.3 1 This method is under the jurisdiction of ASTM Com-mittee D-2 on Petroleum Products and Lubricants.Current edition approved Aug.29,1972.Published Oc-tober 1972.2 The IOOT2 cell available from Balsbaugh Laboratories,25 Industrial Park Rd.,South Hingham,Mass.02043.has been
11、found satisfactory.The glass container provided with this cell is used in cleaning the cell.1 The battery powered model 600B,or other 600 series electrometer available from Keithley Instruments,28775 Au-rora Rd.,Cleveland,Ohio 44139,is satisfaclory.NOTICE:This standard has either been superseded and
12、 replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.5.4 d-c Voltmeter,with a full-scale range not more than about three times the test voltage and an error not more than 3 percent of the full-scale range.3 5.5 Ohmmeter,capable of measuring to
13、 at least l()8(2 with an error of not more than l 0 percent.3 5.6 Stable d-c Voltage Source,which may be either a battery or a well-regulated power sup-ply with a voltage output of 0.8 to l.6 V/mm of electrode gap in the conductivity cell.5.6.1 A suitable voltage source is a 1.5-V battery enclosed i
14、n a metal box(for example,a 4 by 5 by 6-in.aluminum chassis box)equipped with a switch,current limiter,and electrical connections as indicated in Fig.3.5.7 Accessory Parts,required to assemble the apparatus compactly are illustrated in Fig.I.These include:5.7.1 Grounded Metal Base Plate,under the en
15、tire apparatus(fOr example,an aluminum plate 12 in.square by Y in.thick).5.7.2 Metal Support,to raise the electrometer input to the level of the cell center electrode connector(for example,a standard 3.by 6 by 8-in.electrOnics chassis box).5.7.3 Insulating Plate,under the cell assem-bly,about 4 in.s
16、quare and Y4 in.thick,giving not less than I 0 megohms resistance between the cell and the metal plate.Polyethylene or TFE-fluorocarbon is recommended.5.7.4 Sturdy Screen Enclosure,(for visibility of the cell assembly)about 42 in.square and 7 in.high with open back and bottom,(for example,Y4 in.mesh,l/16 in.wire,galvanized hardware cloth,cut and bent to the desired shape,needs no additional support).The screen acts as a Faraday cage to isolate the test cell from external fields.5.7.5 Electrical
