6.3.3 The specimens tested using Type 7 electrodes shall be of such size that all portions of the specimen will be within and no less than 15 mm from the edges of the electrodes during test. In most cases, tests using Type 7 electrodes are made with the plane of the electrode surfaces in a vertical position. Tests made with horizontal electrodes shall not be directly compared with tests made with vertical electrodes, particularly when the tests are made in a liquid surrounding medium.
6.3.4 Keep the electrode surfaces clean and smooth, and free from projecting irregularities resulting from previous tests.If asperities have developed, they must be removed.
6.3.5 It is important that the original manufacture and subsequent resurfacing of electrodes be done in such a manner that the specified shape and finish of the electrodes and their edges are maintained. The flatness and surface finish of the electrode faces must be such that the faces are in close contact with the test specimen over the entire area of the electrodes. Surface finish is particularly important when testing very thin materials which are subject to physical damage from improperly finished electrodes. When resurfacing, do not change the transition between the electrode face and any specified edge radius.
6.3.6 Whenever the electrodes are dissimilar in size or shape, ensure that the one at which the lowest concentration of stress exists, usually the larger in size and with the largest radius, is at ground potential.
6.3.7 In some special cases liquid metal electrodes, foil electrodes, metal shot, water, or conductive coating electrodes are used. It must be recognized that it is possible that these will give results differing widely from those obtained with other types of electrodes.
6.3.8 Because of the effect of the electrodes on the test results, it is frequently possible to obtain additional information as to the dielectric properties of a material （or a group of materials） by running tests with more than one type of electrode. This technique is of particular value for research testing.