[42] Characteristics of commercial radiometers

This chapter discusses the characteristics of commercial radiometers. The configuration of a basic instrument comprises, at minimum, the following components: (1) detector and associated electronics, (2) detector chamber, and (3) injector assembly. A more advanced instrument may have some or all of the following: signal processing, multisample capacity, several injectors, automation, and data processing. In most models, the radiometer accepts light from the entire spectrum of the emitting species and there is no provision to select a portion of the spectrum. However, two new instruments have been described that have filters, which facilitate measuring light over a selected range of wavelengths. Such instruments find use in certain forms of very sensitive luminescence immunoassays and are fitted with two photomultipliers so that a ratio of two separate signals each derived for a separate wavelength range can be obtained simultaneously. Photodiode and photomultipliers are the two types of light detectors used. Photodiodes are currently far less sensitive than photomultipliers.