Abstract
THE three-electrode valve offers a very simple and trustworthy method of amplifying the small currents produced in the thermopile of an infra-red spectrometer. Bright lines are more readily picked up and the limits of absorption bands determined with greater certainty with a valve and telephone than with a galvanometer. Moreover, the valve is instantaneous in action, while a sensitive galvanometer takes an appreciable time to give a trustworthy indication—so much so that the fainter lines are apt to be missed when using a long-period galvanometer. In the thermopile circuit an interrupter is necessary: this may take the form of a steel wire maintained in vibration electrically to which is attached a small wire dipper making contacts through a cup containing mercury. The interrupted thermopile current is passed through the primary of a small step-up transformer the secondary of which is connected to the grid of the valve.
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BELLINGHAM, L. Use of the Triode Valve in Spectrometry. Nature 111, 534 (1923). https://doi.org/10.1038/111534a0
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DOI: https://doi.org/10.1038/111534a0
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