Harold W. Webb

A Null Detector for A.C. Bridge Measurements

A new type of bridge detector is described which has almost constant sensitivity in the frequency range 25 cycles to 70,000 cycles, and which is simple to operate, rugged, and stable.

The Use of Step Weakeners in Photographic Photometry

This paper describes the calibration and use of a five-step weakener in determining the intensities of spectral lines. The employment of a very constant source of radiation consisting of a quartz mercury arc, the voltage of which was held to ±0.2 volt by an air jet controlled by a relay in the arm of a Wheatstone bridge, made the calibration and use of the weakener comparatively simple and rapid. The results of actual measurements are given to illustrate the precision to be expected when using such a weakener.