A capillary mercury-alkaline pick-up with air damping for recording acceleration ballistocardiograms

Summary

The paper gives a description of the design, and presents physical characteristics, of a capillary mercury-alkaline pick-up with air damping, as well as the procedure used in its operation. It is based upon the principle known as the “U effect”, and consists of a capillary tube filled with alternating columns of mercury, alkali, and air. Between each pair of adjoining drops (mercury, alkali) there are provided stops in the shape of penoplast plugs to raise the mechanical stability of the pick-up. The natural frequency of the pick-up may be within the range of 65–300 cycles per sec. The pick-up supplied with mechanical stops is stable and gives curves identical to those described in the literature.