ASTM E780-17(R2021) pdf free download

ASTM E780-17(R2021) pdf free download.Standard Test Method for Measuring the Insulation Resistance of Mineral-Insulated, Metal-Sheathed Thermocouples and Mineral-Insulated, Metal-Sheathed Cable at Room Temperature
1. Scope
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) ther- mocouple or mineral-insulated, metal-sheathed (MIMS) ther- mocouple cable or between the conductors and between the conductors and the sheath, of mineral-insulated, metal- sheathed (MIMS) cable used for industrial resistance thermom- eters. 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 (Al 2 O 3 ). Users of this test method should note that specifica- tions dealing with compacted ceramic insulating materials other than magnesia or alumina, which are described in Specification E1652, are not currently available. 1.3 This test method may be used for thermocouples or MIMS cables having an outside diameter of0.5 mm (0.020 in.) or larger. 1.4 Users of this test method should be aware that the room temperature insulation resistance ofa mineral-insulated, metal- sheathed thermocouple or MIMS cable will change during shipment, storage, or use if they are not properly sealed. 1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.7 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Summary of Test Method
4.1 This test method measures the room temperature (22 6 5°C (72 6 10°F)) dc electrical insulation resistance: (1) in the case of a length of MIMS cable, between each of the thermoelements or conductors and between the thermoele- ments or conductors and the sheath; (2) in the case of either a thermocouple having a single, ungrounded measuring junction or a thermocouple having multiple thermoelement pairs which share a common, ungrounded measuring junction, between the thermoelement pair(s) and the sheath; (3) in the case of a thermocouple having multiple, isolated, ungrounded measur- ing junctions, between each of the thermoelement pairs and between the thermoelement pairs and the sheath. The resis- tance measurements are made with an instrument such as a megohm bridge or megohmeter as described in 6.2. 4.2 In general, because removal of the measuring junction would be necessary, measurement of the insulation resistance between all thermoelements in a thermocouple is not com- monly undertaken. Testing is limited to measuring the insula- tion resistance between the thermoelement pairs and the sheath of the thermocouple and, where possible, the thermoelement pairs. 4.3 Special preparation of a thermocouple will not normally be required, provided that the extension lead wires are clean, undamaged, and sufficiently long to permit connection of the test instrument.