Platinum resistance temperature detectors

There are essentially three basic forms of platinum RTD construction:

· Thin film on a ceramic.

· Ceramic wire wound tubular.

· Glass wire wound tubular.

Platinum is used in these RTD temperature sensors, as it is best suited for precise temperature measurement in preference to other metals and alloys, due to its chemical inertness.

When accuracy, stability, interchangeability or operating temperature is an issue, no other technology can compare.

Platinum RTDs operate on the basis of a change in Ohmic value linear to temperature.

The relationship can best be described by a characteristic polynomial of the form R(t) = RO (1 + At + Bt2) for positive temperatures, where the constants A = 3.9083 E-3°C-1 and B = 5.775 E-7°C-2.

The basic construction of thin film RTD's is a vapour deposition of platinum on a ceramic substrate with photolithography structuring and laser trimming. This enables these sensors to be made in very small sizes, down to 1.5 x 1.5mm.

Heastern Industries carries extensive stocks of thin film PT100s in its Melbourne offices, from the ‘world's smallest’ Minisens PT100 of size 1.5 x 1.5mm to large thin PT100 or PT1000s of size 15 x 30mm - for surface temperature measurements.

Because of the low cost and small size of thin film RTD PT100s, as well as their accuracy, stability and repeatability, these devices are suitable for a wide variety of precision temperature measurements in the food and beverage, paper, automotive, domestic appliance, medical, electronic, communications and energy management markets.

Thin film RTD's are uniquely flexible, being used not only in applications where temperature itself is of importance, but also where information of other related parameters is required.

This information can easily be obtained using temperature as a by-product of the process. This enables thin film RTDs to be used for measuring flow rates, tension, wear levels, and detecting leaks.