A Small and Inexpensive Ultraviolet Dose-Rate Meter Useful in Biological Experiments

Abstract

Although ultraviolet radiations are used extensively in biological experiments, the nonphysicist often finds their measurement tedious and expensive. This article describes a dose-rate meter of good accuracy and precision that is less expensive and more versatile than currently available devices. Because its output depends on wavelength, it is normally useful only where the spectral composition of the radiation is constant, as, for example, with low-pressure mercury arc "germicidal" lamps (emission chiefly at 2537 A) and fluorescent "black light" lamps (emission chiefly at 3000 to 4000 A).2 There are many ways of measuring ultraviolet radiations (1, 2). Some portable devices are described by Luckiesh (3) for use in various ultraviolet regions and fall into two categories, phototube types and photovoltaic-cell types. The phototube types are generally complex, requiring electronic circuits and batteries. A typical one is manufactured by General Electric (4) and is hereinafter referred to as the "GE meter." It consists of a battery-operated phototube with associated circuit and a direct-reading meter, all enclosed in a metal box about 11 x 15 x 16 cm. Its advantages are that it (1) is very sensitive and consequently has a very wide range, (2) comes ready to use, so that calibration is not necessary for the first few years of operation, and (3) has no response to normal room light. Unfortunately, it is expensive and too bulky for many experimental uses. Its complexity and requirement of batteries are further disadvantages. The photovoltaic-cell types are simpler, smaller, less expensive, and require no batteries, but they lack the very high sensitivity of the phototube types. Probably the simplest such device is a small General Electric light meter (photovoltaic cell attached directly to a meter) with an attachment consisting of a layer of zinc