A New Instrument for Measuring X-radiation

Abstract

THE fundamental principle of measurement upon which is based the instrument to be described in this paper is a very old one. It is known in physics as the “null,” “zero,” “compensation,” or “balance” method, and is generally accepted as the most satisfactory procedure for certain types of measurement. The well known Wheatstone bridge and potentiometer, used extensively for electrical measurements, are based on this principle. On the other hand, the apparatus as a whole and the component parts in their special functions have not been employed before for similar purposes, at least to the writer's knowledge. In order to bring out in a simple way the operation of the device, it is well perhaps to start with a mechanical analogy. Everyone is familiar with the weighing of objects by means of a beam balance. Let us analyze the procedure. We wish to determine the weight of, let us say, a coin by means of the simple balance shown diagrammatically in Figure 1. The first thing to do is to check the balance and if it...