This instrument is made for measuring atmospheric pressure with the scale in hPa and the venier which can read to 1/10 mm. Since this precision fortin. INTRODUCTION. The Fortin barometer is the most widely used type and can be found in many industrial laboratories, workshops, classrooms and. A wooden wall plaque supports a brass outer casing which protects the glass barometer tube and wood and leather cistern. A brass screw provides the means .
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With all the mercury removed, the components of the barometer can be carefully cleaned. Fotin other mercury barometers air pressure is calculated from the distance between the level of the mercury in the reservoir and in the tube.
One such is to seal a tube on to the normally closed end of the barometer tube, pump it down in situ, thus drawing up the mercury from the cistern. The pressure is then read from scale D using the Vernier. The correct sequence for measuring pressure with a Fortin or Kew Pattern barometer is: An ivory pin, S, is provided as an index visible through the cistern glass.
With suitably bright background illumination, and taking care to correctly align the front and back setting edges, the vernier cursor V should be lowered until it appears on the summit of the mercury meniscus.
An Improved Fortin Barometer. The evacuation is carried ount in stages: Proper setting can be aided by making small ‘pecking’ dortin movements to ensure that both cursor edges just meet the meniscus. A dirty mercury surface, poorly shaped fiducial point or a partially clogged porous plug P can make proper and repeatable setting very difficult. Arrangement used for filling barometer with a vacuum pump.
Fortin barometer – oi
Publications Our library of publications, posters, training and other useful resources. V is the total volume of mercury in the barometer and A is the effective area of cross section of the cistern. If the barometer is being used in an application where particular measurement uncertainties are needed the barometer should be re-conditioned. All All Title Author Keyword. Figure 1 shows the essential features of the instrument. ofrtin
The cistern C has a lower brass section containing a leather bag, the capacity of which can be adjusted by the screw W. This, of course, is especially important in marine instruments. A Zirconium Oxide Detector for Oxygen. The whole is arranged so that it is possible to read the fortih distance between the tip of the ivory pin S and the lower edge of the vernier V.
Mercury transferred from the bottle on left to that on the right, leaving the dross behind. The leather lining to the cistern should be treated with particular respect as the surface is relatively easily damaged. The cistern and lower section of the barometer tube after removal of the barometer tube housing. NPL collaborates with leading national and international organisations to ensure our science achieves the highest possible impact.
Alternatively, a thin teflon tube is threaded up the barometer tube which is mounted in its normal position and the air pumped out through the trap pictured on the left. In the Fortin barometer the bottom of the reservoir is flexible originally it was made from leather and can be raised or lowered by means of a screw, allowing the surface of fortinn mercury to be adjusted to a predetermined level.
The barometer tube itself should not be lifted at all at this stage, but should be secured by the lower clamp vacated by the brass housing. Firtin pressure in the vacuum line is monitored using a Pirani gauge and should be no greater than 0.
Fortin Mercury Barometer – Physics Museum – The University of Queensland, Australia
Experienced consultants and project managers draw upon a unique combination of industry know-how and world-leading scientific discovery to deliver real-world business solutions and enable innovation and secure competitive advantage. An alternative is to mount the thermometer in a short tube of mercury having the same cross-sectional area as the barometer’s tube, and shielded with the same materials as the barometer’s frame.
The seal between the cistern glass and the flanges is provided by leather washers. Setting the Fiducial Point Fortin barometers only Schematic of Fortin barometerThe lower mercury surface in a Fortin barometer has to be set to a datum level before adjusting its vernier see schematic diagram and the accuracy of pressure measurement depends crucially upon proper setting.
The height of the mercury column is read from the scale on D using the vernier V. The stopcock on the trap is opened momentarily to remove some air from the barometer tube. Here you can find out more about the interesting things we do, science outreach activities you can get involved in or take a look at some of our educational resources. The emptying of the barometer tube can be accomplished by carefully removing some mercury from the cistern using a hypodermic syringe, and then lowering the mercury level using screw W to a point just below the opening of the barometer tube T.
The accuracy of the scale is important also, but can easily be checked with a cathetometer.
Print Save Email Share. The availability of a good vacuum pump makes other methods possible. If the surface is bright and the setting correct, the tip of the point will appear to coincide with its reflected image in the mercury surface.