A portable, stable, standards-quality radiation thermometer was invented that can measure temperatures between -50 °C (-58 °F) to 150 °C (302 °F). The corresponding infrared wavelengths are from 8 to 14 micrometers.
In addition to clinical medicine, temperatures in that region are of urgent importance in applications where contact is not appropriate or feasible; for example, surgeons need to measure the temperature of organs prior to transplant. Modern farmers need accurate temperatures when handling, storing, and processing food. Satellites require non-contact thermometers for measuring temperatures on land and the surface of the sea.
Conventional radiation thermometers often contain little more than a lens for focusing the infrared radiation, and a pyroelectric sensor — a device that converts heat energy into an electrical signal. The measurements can be affected by temperature differences along the thermometer and by temperature outside the instrument.
The new Ambient-Radiation Thermometer (ART) is fitted with a suite of interior thermometers that constantly gauges temperatures at different points in the instrument. Those readings are sent to a feedback loop system that keeps the 30-cm (12-inch) cylinder containing the detector assembly at a constant temperature of 23 °C (72 °F).
After it has been calibrated against standards-grade contact thermometers, the instrument can remain stable to within a few thousandths of a degree for months under continuous operation. That makes the system very promising for applications that involve remote sensing over long periods.
There are several methods of making very-high-accuracy temperature measurements but few are well-suited to field work. Platinum resistance thermometers are fragile and need frequent recalibration. The standard temperature source for transferring that calibration to the ART involves a heat-source cavity inside about 42 liters (11 gallons) of liquid.