A device to measure a temperature of molten metal may include an infrared sensor effective to measure the temperature of the molten metal, a sheath having an open end, a sealed end, and a channel extending from the open end to the sealed end, and an infrared-transparent window disposed between the infrared sensor and the channel of the sheath. The open end of the sheath is disposed near the infrared sensor and the sealed end of the sheath extends into the molten metal. The infrared-transparent window or rod is disposed between the infrared sensor and the channel of the sheath such that the infrared sensor can measure the temperature through the infrared-transparent window or rod, the channel, and the sealed end. The infrared-transparent window or rod seals the infrared sensor from the channel in the sheath.