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用热电偶在氧化性介质中测量高温有很大的困难。最适合于氧化性介质的铂铑-铂热电偶只能用至1600℃。其它贵金属和合金,例如:铱、铱钌、铱铑合金等制成的热电偶热电势均较低,而且很不稳定,价格也极其昂贵。不同含铼量的钨铼合金制热电偶可供测温至2400℃,但它只能在真空或还原性介质中使用,由于钨在高温下与氧发生活性互反应,故这种热电偶不适于在氧化性介质中应用。实验表明,如果将热电偶的工作端敷一层铱保,护层(见附图),其未用铱保护的偶丝部分装在耐火陶瓷管内,则钨铼合金热电
Thermocouples in the oxidizing medium to measure high temperature have great difficulties. Platinum and rhodium - platinum thermocouples most suitable for oxidizing media can only be used up to 1600 ° C. Other precious metals and alloys, such as: iridium, iridium ruthenium, iridium rhodium alloy thermocouple made of low thermal potential, but also very unstable, the price is extremely expensive. Different rhenium content of the rhenium alloy thermocouple available for temperature measurement to 2400 ℃, but it can only be used in a vacuum or reducing medium, due to tungsten in the high temperature and oxygen active interaction, so the thermocouple discomfort Used in oxidizing media. Experiments show that if the working end of the thermocouple coated with an iridium Paul, the protective layer (see photo), which is not part of the iridium wire protection installed in the refractory ceramic tube, the tungsten rhenium alloy thermoelectric