The present invention relates to a high-temperature thermocouple with a thermocouple wire including two dissimilar wires twisted together and covered with a polyimide-based leak-proof insulation coating. The thermocouple wire may include a welded hot junction attaching the two dissimilar wires together on one end and may be connected to a thermocouple connector located at an opposite end. A method for making the high-temperature thermocouple may include coating a pair of dissimilar wires with a leak-proof polyimide-based insulation coating by dipping of dissimilar wires in a liquid polyimide-based solution and curing the dissimilar wires with heat. The method may also include twisting the dissimilar wires around themselves, welding together the dissimilar wires to each other creating a welded hot junction, and attaching the opposite end of the dissimilar wires to a thermocouple connector. The leak-proof insulation coating and thermocouple connector may be rated for 800 degrees F. and 150 PSI.
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