Verification items and methods for platinum rhodium thermocouples

Verification items and methods for platinum rhodium thermocouples:

The number, size, and surface of thermocouples should be checked with a steel tape measure, vernier caliper, and visual acuity to ensure compliance with requirements.

Newly manufactured thermocouples that have passed the surface review should be annealed at the highest calibration point temperature for 2 hours before calibration, and then cooled in the furnace to below 250 ℃. Thermocouples in use should not be annealed.

The temperature for verifying the indication of thermocouples is determined by the thickness of the thermocouple wire and electrode diameter, as shown in Table 3.

The calibration of points below 300 ℃ is carried out in an oil constant temperature bath, and compared with a second-order mercury thermometer, the temperature change in the oil bath during calibration does not exceed ± 0.1 ℃.

Cover the two electrodes of the thermocouple with high aluminum insulated ceramic beads, approximately 50mm in size, and thread a plastic sleeve through the tail end, exposing 20mm in size at the tail end to connect with the reference terminal lead.

The thermocouple reference wire should be made of the same material as the copper wire to stop the connection. The resistance of the copper wire at 20 ℃ should be less than 0.01724 μ Ω· m.

Place a glass maintenance tube on the measuring end of the thermocouple, pull it out of the oil constant temperature bath, with a depth of not less than 300 mm. Cover the glass tube mouth around the thermocouple with degreased cotton.

Pull the reference end of the thermocouple out of the glass or plastic tube containing transformer oil or alcohol, and then evacuate and pull it out of the freezing point thermostat. The pulling depth should not be less than 150 mm.

The above are the calibration items and methods for platinum rhodium thermocouples. We hope everyone can grasp them.