What are the examples of primary and secondary thermometers?

Primary thermometers include devices like Mercury thermometers and gas thermometers, which are designed to measure temperature based on fundamental physical principles without relying on calibration against other standards. Secondary thermometers, on the other hand, are calibrated against primary standards and include digital thermometers, infrared thermometers, and bimetallic thermometers, which are commonly used for practical applications in various fields. These secondary devices are often more convenient for everyday use but may require periodic calibration to ensure accuracy.