An Instrument for Measuring Very Small Displacement or Motion and Its Various Applications

OBATA Jûichi

doi:10.11526/ieejjournal1888.48.38

In the present article are described the detailed construction and various examples of applicatons of the "Ultramicrometer", a new instrument for measuring small displacement or motion utilizing a generating valve circuit. In its usual form the instrument consists of a tuned grid circuit, but it can easily be changed to the Colpitts-Hartley circuit. The displacement or motion to be measured is made to produce either a change in the capacity in the circuit or a change in the eddy-current loss, and in consequence a corresponding change in the anode current of the valve is resulted. This change in the anode current is measured with a galvanomter, or if a permanent record is needed, an Einthoven string galvanometer or a Duddell oscillograph is employed. The anode current itself is balanced by means of the potentiometer method or a small transformer is inserted in the anode circuit.<br>With this instrument the capacity method as well as the eddy-current method may be carried out, and the anode current may be balanced or a transformer may be inserted, all the necessary resistances and transformer being contained in the instrument.<br>As the examples of applications of the instrument are described the recording of earth-movements, direct recording of accelerations, an electrical indicator for high-speed internal-combustion engines, precise recording of sounds, pressure-variations and various mechanical vibrations.

An Instrument for Measuring Very Small Displacement or Motion and Its Various Applications

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