Standard Test Method for Measuring the Insulation Resistance of Mineral-Insulated, Metal-Sheathed Thermocouples and Mineral-Insulated, Metal-Sheathed Cable at Room Temperature

Importancia y uso:

5.1 Thermocouples fabricated from thermocouple cable that has been contaminated by moisture or by other impurities may undergo large changes in thermoelectric properties or may fail catastrophically when exposed to high temperatures. Since such contamination usually lowers the electrical resistance between the thermoelements and the sheath substantially, measurement of the insulation resistance can provide a valuable check of insulation quality and cleanliness, and can serve as a basis for rejection of unsuitable material and unreliable components. For manufacturers in particular, low electrical insulation resistance can also be indicative of displaced thermoelements or conductors or defects in the metal sheath which will require further investigation, but all users should be aware of these potential defects when faced with an unacceptable insulation resistance measurement.

5.2 This test method is primarily intended for use by manufacturers and users of mineral-insulated, metal-sheathed (MIMS) thermocouples or MIMS cables to verify that measured values of insulation resistance exceed specified minimum values, such as those listed in Specifications E235, E585/E585M, E608/E608M, E2181/E2181M, and E2821. Manufacturers and users should be aware, however, that when the insulation resistance is greater than 1 × 10⁸ Ω, disagreement by an order of magnitude in the results obtained with this test method is not unusual. In addition, users of this test method should appreciate that the room temperature insulation resistance of both MIMS cables and of finished thermocouples will change during shipment, storage, and use if the end seals are damaged or defective. Consequently, values of insulation resistance determined by this test method may not necessarily be repeatable.

Subcomité:

E20.14

Referida por:

E1350-18R23, E0235_E0235M-23, E0608_E0608M-13R19, E0344-23, E0585_E0585M-23, E2821-20, E0839-23, E2846-20, E0608_E0608M-13R19

Volúmen:

14.03

Número ICS:

17.200.20 (Temperature-measuring instruments)

Palabras clave:

insulation resistance; mineral-insulated, metal-sheathed (MIMS) thermocouple cable insulation resistance; mineral-insulated, metal-sheathed thermocouple insulation resistance;