符合UL817第89.4条标准要求，配合7#铅珠（OD 0.10 inch (2.5 mm)）测试，适用于UL插头两插和三插测试绝缘电阻用。与绝缘电阻测试机配合才能使用。
89 Insulation Resistance Test
89.1 The insulation resistance of a ﬁtting shall not be less than 100 megohms between:
a) Live parts of opposite polarity,
b) Live parts and dead metal parts that are exposed to contact by persons or that may be grounded in service, and
c) Live parts and any surface of insulating material that is exposed to contact by persons or that may be in contact with ground in service.
89.2 To determine compliance with 89.1, the insulation resistance is to be measured by a magneto megohmmeter which has an open-circuit output of 500 V or by equivalent equipment.
89.3 The use of a megohmmeter between live parts requires no special clariﬁcation or instruction.
However, in measuring insulation resistance to the surface of an insulating material, it is necessary to apply the electrode to the insulating material as described in 89.4.
89.4 A quantity of No. 7 lead drop shot [approximate diameter 0.10 inch (2.5 mm)] is to be placed in a container which is open at the top. After cord holes or other openings through which the shot can enter have been plugged carefully with a high-resistance insulating material, the ﬁtting is to be immersed in the shot so that the shot serves as an electrode in contact with the surface to which the test is to be applied.
89.5 All rubber parts are to be kept for at least 48 hours at room temperature before being subjected to the test mentioned in 89.1 – 89.4.