Cathetometer
Encyclopedia
A cathetometer is an instrument for measuring vertical distances in cases where a scale cannot be placed very close to the points whose distance apart is desired.
The instrument consists essentially of an accurately graduated scale and a horizontal telescope
capable of being moved up and down a rigid vertical column. The position of the telescope can be read by means of an attached Vernier scale
. In measuring the vertical distance between two points, the instrument must first be leveled. Next, the cross hair in the eyepiece of the horizontal telescope is brought into coincidence with the image of one point and the position of the telescope noted; the cross hair is then brought into coincidence with the image of the other point and the new position of the telescope noted. The difference between these readings is the vertical distance required.
Among the uses of a cathetometer is reading the levels of a liquid in a capillary tube, such as in measurements of surface tension
. A cathetometer also can be used for following the changes in liquid level in a dilatometer
due to, for example, a chemical reaction therein.
The instrument consists essentially of an accurately graduated scale and a horizontal telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
capable of being moved up and down a rigid vertical column. The position of the telescope can be read by means of an attached Vernier scale
Vernier scale
A vernier scale is an additional scale which allows a distance or angle measurement to be read more precisely than directly reading a uniformly-divided straight or circular measurement scale...
. In measuring the vertical distance between two points, the instrument must first be leveled. Next, the cross hair in the eyepiece of the horizontal telescope is brought into coincidence with the image of one point and the position of the telescope noted; the cross hair is then brought into coincidence with the image of the other point and the new position of the telescope noted. The difference between these readings is the vertical distance required.
Among the uses of a cathetometer is reading the levels of a liquid in a capillary tube, such as in measurements of surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
. A cathetometer also can be used for following the changes in liquid level in a dilatometer
Dilatometer
A dilatometer is a scientific instrument that measures volume changes caused by a physical or chemical process. A familiar application of a dilatometer is the mercury-in-glass thermometer, in which the change in volume of the liquid column is read from a graduated scale...
due to, for example, a chemical reaction therein.