Effects of Misalignment on the Accuracy of Blackbody Cavity Sensor for Temperature Measuring

Abstract

Blackbody cavity temperature sensor has been used in the field of radiation temperature measurement since its applicability in measuring the temperature of a liquid. A detector is always placed coaxially with the cavity to receive the radiant energy from the bottom of the cavity where the temperature is the same as the liquid to be measured. However, the accuracy problem still exists. Due to the deviation of the sensor’s relative position, there is a deviation angle between the axis of the detector and of the cavity, which will cause the detector receives the radiation from the low radiant energy regions of the measuring cavity, and lead to a low precision of the measurement result. In this article, research is made to analyze the effects of the misalignment between the cavity and the detector as well as the influence of the length of isothermal zone and spot size when the detector is out of the axis. To verify the situations above, we set experiments that reference the actual conditions, results show good agreement with theoretical analysis. The results are helpful for the optimum parameter design of the blackbody cavity as well as determine the relative position of the detector and the cavity.