Temperature detection today offers a wide variety of sensors: thermocouples, thermistors, radiationpyrometers, and RTDs (resistance thermometer devices).
Platinum resistance thermometers are the most widely recommended sensor of choice. They provide high reliability, long-term stability, interchangeability and meet internationally approved standards. Platinum temperature sensors can also be used over wide temperature spans, e.g. -250°C to +850°C.Through additional packaging they can be used in the most severe environments.
In the recent years, Platinum resistance elements have been the trendsetter in establishing a unified processing signal. Worldwide acceptance of IEC751,2:1996-07(DIN-EN 60751:1996-07) further confirms Platinum's superiority, in comparison to other metals such as copper or Nickel, as the international standard of choice.
For many years, Platinum temperature sensors were primarily limited to the industrial processing industries, because of high price and physical characteristics. Lower cost spreading resistors (NTC's/PTC's) were generally used by the consumer goods' industries.
Thermistors are temperature sensitive resistors that exhibit large resistance change over small temperature ranges. They are comprised of sintered metal oxides with a high specific resistance values. Increases in temperature result in decreases in resistance in a predetermined ratio (NTC= negative temperature coefficient).
PTC-sensors (positive temperature coefficient) are made of a semiconductive polycrystaline ferro electrical ceramic material. The resistance of a PTC increases as temperature rises.
Material and production specific attributes precluded these sensors from an international standardization.
The sensor market for thermistor and Platinum temperature sensors are both traditionally and geographically separated. The development of thermistors offered an alternative to thermocouples throughout US industries. In Europe, Platinum temperature sensors became the preferred alternative for industrial temperature measurement.
Thermistors feature small physical dimensions, low price, fast response time, and high specific values. These positive attributes allowed for thermistors to gain strong market shares in the consumer goods, automotive and electronic industries. However they also exhibit an inherent wide deviation in their characteristic resistance values which can negate many of their advantages.
The decision as to which sensor is best for your application, Platinum temperature sensors or Thermistors (NTC's/PTC's) should be viewed from both commercial and technical aspects.
Interchangeability is one of the most important criteria for sensors. Thermistors, by their nature, are limited in their ability to be interchaged. On their other hand, Platinum temperature sensors are produced to accepted international standards, specific ohmic values and reproduceable temperature coefficients thus providing ensured interchangeability.
Preference is also given to Platinum temperature sensors because of the inherent long term stability in relation to both time and temperature cycling. You also achieve tighter accuracy and stability with Platinum temperature sensors.
Size reduction, originally an exclusive benefit of thermistors, is now achieveable with Platinum temperature sensors. Platinum temperature sensors are now available in widths less than 1 mm, and lengths less than 2 mm.
Basic standard resistance values for Platinum temperature sensors are available in a wide variety such as: 10, 20, 50, 100, 200, 400, 500, 1000 and 2000 ohms.
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