Resistance temperature detectors

Citation

(1998), "Resistance temperature detectors", Sensor Review, Vol. 18 No. 2. https://doi.org/10.1108/sr.1998.08718baf.007

Resistance temperature detectors

Resistance temperature detectors

Keywords Resistance, Sensors, Temperature, Temperature detectors

Resistance temperature detectors (RTDs) are replacing other types of temperature sensors in the USA, such as thermocouples and thermistors. RTDs have always been widely used for high accuracy but often lost out to thermocouples in high-temperature applications. Now it is possible to buy a rugged, industrial RTD capable of operation to 850°C (1,562°F). Temperatures as high as 1,100°C (2,012°F) are on the horizon. The new precision RTDs bring laboratory precision to field applications. An example is a portable temperature calibrator that uses a precision platinum RTD as its internal reference, allowing the manufacturer to claim 0.05°C stability to 700°C.

At more moderate temperatures, thin-film RTDs increasingly replace wire-wound sensors. Standardisation and automation have made an inexpensive commodity of platinum thin-film RTDs with TCs of 0.00385. Basic sensing elements cost less than $5 in unit quantities; 100 and 1,000-‡ base resistances are common. "A recent arrival is the 10,000-‡ thin-film RTD, which provides a sensitivity of 39-‡/°C", explains Brian Jones of Minco Products Inc. in Minneapolis. "This will put it in competition with thermistors for medical applications requiring high resolution around a narrow range. The high base resistance also requires less measuring current, helping to conserve battery power in portable devices."

RTD makers say the challenge is to package thin-films and other elements in innovative configurations to improve thermal response, simplify installation, or adapt to harsh environments. An example is a flat, laminated thermal-ribbon RTD using a thin-film sensor. It mounts easily to surfaces with self-adhesive backing and features a tough polyamide jacket and Teflon leads.