NIST Ambient Radiation Thermometer (image) National Institute of Standards and Technology (NIST) Share Print E-Mail Caption Operation of the NIST Ambient Radiation Thermometer, which is approximately 60 cm (24 in.) long: (1) Infrared (IR) light from a fixed-temperature calibrated source (at right, not shown) enters the thermometer enclosure through this lens, which focuses the radiation onto a "field stop," analogous to the f-stop aperture in photography. (2) A circular metal chopper slices the IR beam into a sequence of pulses. (3) The first lens inside the central cylinder converts the light from the field stop to a parallel beam. (4) The light passes through this insulated cylinder about 30 cm (12 in.) long, which is temperature-controlled by a feedback system. Stray radiation is blocked by another stop. (5) A second lens focuses the light onto a pyroelectric detector. (6) The detector output is routed to an amplifier that boosts the signal to readily readable levels. Credit NIST Usage Restrictions Please credit NIST when using this image. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.