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Cathetometer
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.This text is copied fro''A Handbook of Physics Measurements''by E. S. Ferry, 1914, volume 1 Among the uses of a cathetometer is reading the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cathetometer
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.This text is copied fro''A Handbook of Physics Measurements''by E. S. Ferry, 1914, volume 1 Among the uses of a cathetometer is reading the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Travelling Microscope
A travelling microscope is an instrument for measuring length with a resolution typically in the order of 0.01mm. The precision is such that better-quality instruments have measuring scales made from Invar to avoid misreadings due to thermal effects. The instrument comprises a microscope mounted on two rails fixed to, or part of a very rigid bed. The position of the microscope can be varied coarsely by sliding along the rails, or finely by turning a screw. The eyepiece is fitted with fine cross-hairs to fix a precise position, which is then read off the vernier scale. "Merriam-Webster Dictionary Some instruments, such as that produced in the 1960s by the Precision Tool and Instrument Company of Thornton Heath, Surrey, England, also measure vertically. The purpose of the microscope is to aim at refere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telescope
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, the word ''telescope'' now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The first known practical telescopes were refracting telescopes with glass lenses and were invented in the Netherlands at the beginning of the 17th century. They were used for both terrestrial applications and astronomy. The reflecting telescope, which uses mirrors to collect and focus light, was invented within a few decades of the first refracting telescope. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. Etymology The word ''telescope'' was coin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vernier Scale
A vernier scale, named after Pierre Vernier, is a visual aid to take an accurate measurement reading between two graduation markings on a linear scale by using mechanical interpolation, thereby increasing resolution and reducing measurement uncertainty by using vernier acuity to reduce human estimation error. It may be found on many types of instrument measuring linear or angular quantities, but in particular on a vernier caliper which measures internal or external diameter of hollow cylinders. The vernier is a subsidiary scale replacing a single measured-value pointer, and has for instance ten divisions equal in distance to nine divisions on the main scale. The interpolated reading is obtained by observing which of the vernier scale graduations is coincident with a graduation on the main scale, which is easier to perceive than visual estimation between two points. Such an arrangement can go to a higher resolution by using a higher scale ratio, known as the vernier constant. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Tension
Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged. At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). There are two primary mechanisms in play. One is an inward force on the surface molecules causing the liquid to contract. Second is a tangential force parallel to the surface of the liquid. This ''tangential'' force is generally referred to as the surface tension. The net effect is the liquid behaves as if its surface were covered with a stretched elastic membrane. But this analogy must not be taken too far as the tension in an elastic membrane is dependent on the amount of deformation of the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. Because mercury has a fairly constant rate of expansion over ambient temperature ranges, the volume changes are directly related to temperature. Applications Dilatometers have been used in the fabrication of metallic alloys, study of martensite transformation, compressed and sintered refractory compounds, glasses, ceramic products, composite materials, and plastics.Hans Lehmann, refuge Gatzke '' Dilatometry and differential thermal analysis for the evaluation of processes ''? ? , 1956. Dilatometry is also used to monitor the progress of chemical reactions, particularly those displaying a substantial molar volume change (e.g., polymerisation). A specific example is the rate of phase changes. In food scienc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
