Precision and Accuracy Improvements to the Technical Measurements, Inc. Solar Radiometer System

摘要

A Technical Measurements, Inc. radiometer system, purchased for solar irradiance measurements in 1976, has been modified to improve both precision and accuracy. The sum of systematic errors is now calculated at +-0.7% (+-0.3% rms combination of errors) for insolation data during good viewing conditions. Problem origins and solutions are listed for wind; sunlight on the control unit; power supply drifts; amplifier thermal drifts; pickup in the control cable; digital panel meter zero, nonlinearity, and sensitivity; loading by operate pilot; zero of calibration voltage and current; coarse settings of TARE, AMP ZERO, and SCALE pots; zero shifts; noise; shading of the radiometer during calibration; thermal response time; radiometer blocking; and temperature compensation. Errors are detailed for measuring voltage and current during calibration (0.1%), for use of a measurement procedure that is prescribed (approx. 0.2%, mostly from aureole uncertainties), and for inequivalencies of electrical and optical heating (approx. 0.4%). Techniques are advanced that should allow reducing the error sum to +-0.3% (+-0.1% rms), but a considerable effort is required. (ERA citation 09:014899)