A PERIODIC RADIOMETER FOR ELIMINATING DRIFTS

Abstract

It is shown that while the Pfund resonance radiometer reduces the effect of drifts by a factor of several hundred, its advantage over the conventional Moll amplifying system as regards the reduction of the effect of Brownian motion on the accuracy of the readings is only about a factor of three for a resonance radiometer system requiring 140 seconds for a single observation. For a Moll system and a resonant system of equal times of observation, the Moll system is about twice as good as regards Brownian error in the readings. A resonance radiometer loses both its Brownian advantage and its ability to reduce drifts, when designed for a short time of response.A periodic radiometer particularly suitable for rapid recording is described, drifts being completely eliminated, while the time of response is only six seconds. Two condensers in series with the amplifying circuit effectually stop all drifts while passing the periodic deflections. By averaging visually a considerable number of deflections, the accuracy of the resonance radiometer for equal reading time can be approached so that the same instrument may serve both for rapid exploration of spectra and more careful determination of detail.Infrared spectra of high resolution have been successfully recorded from a grating spectrometer and in amount of detail shown, closely approach the most carefully manually recorded curves.