When insulation type sheathed thermocouple is under ambient temperature 20±150C and relative humidity not more than 80%, insulation resistance between thermode and outer casting tube should comply with the stipulations in the table below:
| Diameter of sheathed thermocouple | Test voltage | Insulation resistance |
| 0.5〜1.5 | 50±5 | >1000 |
| >1.5 | 500±50 | >1000 |
Note: Insulation resistance is indicated as MO*m, which means insulation resistance of specimen with length 1m is 1000 MO and that of specimen with length 10m is 100 MO.
