Long term behavior of thermometers with pyroelectric detectors

While photon detector-based radiation thermometers form the basis for primary traceable radiation thermometry above the silver-point, their use below the silver point is limited due to lack of thermal radiation at lower temperatures. There is some work being done with these type of detectors down to 0 °C. However, in this region, there are radiation thermometers being used for traceable calibration work which are pyroelectric detector-based instruments. This family of radiation thermometers went under great scrutiny as traceable instruments during the TRIRAT project. Fluke Calibration’s American Fork Laboratory has established traceability using radiation thermometers with pyroelectric detectors. The work on this project began in 2006, with traceable calibrations being done starting in 2007. Since this time, a significant amount of data has been accumulated on four reference standards. The data are applied to these standards for use in calibrating flat plate thermal radiation sources. The data are also used as a quality control on each radiation thermometer’s drift. This paper presents this drift history of over 15 years. It discusses the initial drift observed on the instruments, plus the steady state drift observed in these instruments. It also looks at the repeatability of these calibrations looking at the variance of these readings over time. An examination of any other time related factors with these radiation thermometers is considered.