Precautions and installation requirements for on-site use of platinum rhodium thermocouples?

Platinum rhodium thermocouple is a commonly used temperature measuring element in temperature measuring instruments. It directly measures temperature and converts the temperature signal into a thermoelectric potential signal, which is then converted into the temperature of the measured medium through electrical instruments (secondary instruments). The installation methods of platinum rhodium thermocouples include: threaded connection, flange connection, and welding. Their applicability and requirements vary, mainly depending on parameters such as pressure and temperature. So what should we pay attention to when using and installing platinum rhodium thermocouples on site?

1. When using platinum rhodium thermocouple compensation wires, attention must be paid to model matching, polarity cannot be connected incorrectly, and the temperature at the connection end between the compensation wire and the platinum rhodium thermocouple cannot exceed 100 ℃.

2. When using a platinum rhodium thermocouple with a large time constant for temperature measurement or control, although the temperature displayed on the instrument fluctuates very little, the actual furnace temperature may fluctuate greatly. In order to accurately measure temperature, platinum rhodium thermocouples with small time constants should be selected.

3. After correctly wiring and powering on according to the instrument wiring diagram, the instrument first displays the platinum rhodium thermocouple index number of the instrument, then displays the instrument range, and then the digital tube in the lower row of the instrument displays the set temperature, and the digital tube in the upper row of the instrument displays the measured temperature.

4. Platinum rhodium thermocouples cannot be installed in areas where the measured medium rarely flows. When measuring the gas temperature inside a tube with a platinum rhodium thermocouple, it must be installed against the flow velocity direction and fully in contact with the gas.

5. In order to ensure sufficient heat exchange between the measuring end of platinum rhodium thermocouples and thermal resistors and the measured medium, the measuring point position should be selected reasonably, and efforts should be made to avoid being located in the valve

6. According to the law of intermediate conductor, in practical temperature measurement applications of platinum rhodium thermocouples, the form of hot end welding and cold end open circuit is often used. The cold end is connected to the display instrument through a connecting wire to form a temperature measurement system.