Microtasimeter

An apparatus for indicating minute changes in temperature or atmospheric moisture.

A button of compressed lampblack is placed in series with a battery and galvanometer. A strip of some substance, affected in its length either by heat or by moisture, is held pressing against the button. A slight change in length of the strip varies the resistance of the button and hence affects the galvanometer. In this way exceedingly slight changes in heat or moisture may be indicated.

For heat indications vulcanite may be used. The heat of the hand held near it is enough to affect the galvanometer. For moisture a slip of gelatine is used. The moisture of a damp slip of paper two or three inches distant is sufficient to affect the galvanometer.

In the cut, Fig. 2, shows the general distribution of the apparatus in circuit with a battery and galvanometer. C is the base of the apparatus, from which the standard, B, with adjusting screw, H, rises. The strip of vulcanite is held between I and G. Within D is the carbon button (F in Fig. 3) pressed between G and E; A is a standard to carry the parts last described. In Fig. I it is shown as part of a Wheatstone bridge, a, b and c being resistance coils; l the tasimeter, and g the galvanometer. If a balance is secured, any variation in the resistance of the tasimeter will disturb the galvanometer.

Synonym: Tasimeter.

Fig. 243. MICROTASIMETER.