Abstract
National metrology institutes around the world and other calibration facilities interested in highly precise (~±0.02% k=2), SI traceable radiance calibrations use Absolute Cryogenic Radiometers (ACRs) to set their optical power measurement scale. An ACR system consists of a highly absorptive optical receiver cavity that is operated around 4 K and below, and an electronics package that is used to control and report measured power readings from the receiver cavity. There are commercial electronics specifically designed for ACR calibrations currently available, but these complete systems can be difficult for the end-user to modify or upgrade. In addition, the Low Background Infrared (LBIR) Facility at NIST is interested in making lower power measurements than are supported in the commercially available systems. In an effort to develop a research calibration system which can be easily assembled and modified, the LBIR Facility has used commercial off-the-shelf (COTS) components such as AC resistance bridges and tabletop voltmeters to build up a system for ACR optical power calibrations. In this presentation we will compare the results of the new COTS ACR electronics with those from a set of commercial ACR electronics. Optical measurement data will be used to demonstrate the accuracy, repeatability, power range, and data acquisition time for the new calibration system.
Absolute Cryogenic Radiometer Control Using Commercial Off-the-Shelf Electronics
National metrology institutes around the world and other calibration facilities interested in highly precise (~±0.02% k=2), SI traceable radiance calibrations use Absolute Cryogenic Radiometers (ACRs) to set their optical power measurement scale. An ACR system consists of a highly absorptive optical receiver cavity that is operated around 4 K and below, and an electronics package that is used to control and report measured power readings from the receiver cavity. There are commercial electronics specifically designed for ACR calibrations currently available, but these complete systems can be difficult for the end-user to modify or upgrade. In addition, the Low Background Infrared (LBIR) Facility at NIST is interested in making lower power measurements than are supported in the commercially available systems. In an effort to develop a research calibration system which can be easily assembled and modified, the LBIR Facility has used commercial off-the-shelf (COTS) components such as AC resistance bridges and tabletop voltmeters to build up a system for ACR optical power calibrations. In this presentation we will compare the results of the new COTS ACR electronics with those from a set of commercial ACR electronics. Optical measurement data will be used to demonstrate the accuracy, repeatability, power range, and data acquisition time for the new calibration system.