A stable, inexpensive, solid-state photomultiplier photometer

Abstract

Many laboratories studying bioluminescent or chemiluminescent systems are measuring the light emission using a photomultiplier photometer designed by E. F. MacNichol in about 1952 (1). In the time since the design of that photometer, enormous advances have occurred in electronics which allow for the modernization of its circuitry. Unfortunately, the commercially available equivalents of the MacNichol photometer have lagged in modernization; moreover, they have never incorporated one of its key features, namely, accurately calibrated gain settings controlled by the high voltage applied to the phototube. In addition, some commercial units are needlessly expensive. Although a satisfactory instrument can be assembled from commercial units (incorporating a highvoltage supply and a microammeter) this instrument would lack the calibrated gain settings, and is also not inexpensive. The present paper describes a modern, miniaturized, solid-state photometer that possesses the stability and accuracy of the original Mac-Nichol design along with its calibrated gain settings. In addition, the photometer has been designed to supply up to 2000 V so that it may be used with end-window photomultipliers requiring this higher operating voltage.