ASTM E780-2017 测量室温下矿物绝缘的金属铠装热电偶和热电偶电缆绝缘电阻的试验方法 Standard Test Method for Measuring the Insulation Resistance of Mineral-Insulated, Metal-Sheathed Thermocouples and Mineral-Insulated, Metal-Sheathed Cable at Room Temperature

1.1 This test method provides the procedures for measuring the room temperature electrical insulation resistance between the thermoelements and between the thermoelements and the sheath, of a mineral-insulated, metal-sheathed (MIMS) thermocouple or mineral-insulated, metal-sheathed (MIMS) thermocouple cable or between the conductors and between the conductors and the sheath, of mineral-insulated, metal-sheathed (MIMS) cable used for industrial resistance thermometers. It may be used to measure the insulation resistance of bulk lengths of mineral-insulated, metal-sheathed MIMS cable previously sealed against moisture intrusion or to test a thermocouple having an ungrounded measuring junction. This method cannot be used to test a thermocouple having a grounded measuring junction unless the measuring junction is removed prior to testing, after which the thermocouple may be dealt with in the same manner as a mineral-insulated, metal-sheathed (MIMS) cable. 1.2 This test method applies primarily to thermocouple cables and cable used for industrial resistance thermometers conforming to Specifications E585/E585M, E2181/E2181M, and E2821 and to thermocouples conforming to Specifications E608/E608M and E2181/E2181M, but may also be applied to thermocouples or MIMS cables that are suitable for use in air, whose sheath or thermoelements or conductors are comprised of refractory metals, that are tested in a dry and chemically inert environment, and that may employ compacted ceramic insulating materials other than magnesia (MgO) or alumina (Al2O3). Users of this test method should note that specifications dealing with compacted ceramic insulating materials other than magnesia or alumina, which are described in Specification E1652, are not currently available. As a result, acceptance criteria must be agreed upon between the customer and supplier at the time of purchase, or alternatively, judgment and experience must be applied in establishing test voltage levels and