One of the types of temperature measurement resistors, there are platinum type resistors as temperature sensors that have been widely used for a long time. The platinum type is platinum wire wound type temperature sensors, also called Pt100, which are conformed to JIS or IEC. This product is quite costly due to its platinum wire. However, they have excellent environmental characteristic and long-term stability. High linearity as mentioned above, has the characteristics that follow the calculations and the conversion table for temperature and resistance values given in JIS and IEC standard. Platinum wire wound types have higher price than other resistance temperature sensors. Moreover, the products with resistance at 100or over, the size becomes larger and the price is much higher. Therefore, the platinum wire wound types have been considered as high-priced temperature sensors by design engineers.

KOA Corporation have been producing on a commercial scale, low-price, thin-film platinum resistance thermometer sensors of high resistance value. Although the products were based on the company's own temperature precision technologies, they have been used regularly for measurement equipment as high-precision and high-stability products. About ten years earlier, KOA Corp. produced on a commercial scale thin-film platinum resistance thermometer sensors conformed to the JIS standard. Some design engineers had concerns about reliability when thin-film platinum resistance thermometer sensors would be used instead of wire wound resistance thermometer sensors. After about two years, the reliability of thin-film types became widely recognized and demand for thin-film platinum resistance thermometer sensors consequently increased.

Recent increase in demand of them have been resulted from the facts that various designs require high-precision temperature sensor or customized products for improvement of the added value of set, and that harder temperature control of food processing has been regulated by new law.

The factors that thin-film platinum resistance thermometer sensors have been accepted in the market; Almost the same performance as wire wound types, low price, thin-film and small products with high resistance value(1k), large resistance change and few errors by resistance of lead wire. Those enabled the designing of circuit in set easily.

The demand of customized platinum resistance thermometer sensors has been
increasing lately. The need for new shape e.x. temperature sensors mounted on glass epoxy board or the molded products. This trend is expected to become more evident as domestic set manufacturers in Japan get their high value-added designs more.