This paper presents an experimental study of the angular response of an ellipsoidal radiometer performed using a 25 mm diameter variable temperature blackbody as a radiant source. The radiometer consists of a highly reflective ellipsoidal cavity with a thermopile sensor at one focus, and the aperture located at the other focus. The measured angular response was symmetrical and showed a smooth variation in the angle range -90' to +90'. However, the departure from the expected cosine dependence was significant. Therefore, a correction to the radiometer responsivity was determined based on the difference between the measured radiometer response and the cosine response of the sensor. The sensor cosine response was defined with reference to the flux level at the sensor location inside the radiometer. The application of the correction factor showed good agreement between the calculated and the measured responsivity of the radiometer.
Citation: National Conference of Standards Laboratories International
Pub Type: Journals
heat flux, radiometer, sensors