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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Oxide and dust have to be removed and this can be done using a hypodermic syringe to draw the mercury away from the dross.
The two clamps holding the brass housing are slackened and the brass housing carefully raised thus exposing a section of the barometer tube still resting in the cistern. A brass screw provides the means to raise or lower the level of mercury in the cistern to a fiducial point in the form of an ivory pointer. The correct sequence for measuring pressure with a Fortin or Kew Pattern barometer is: The upper section of the the cistern consists of a wide glass tube clamped between the upper and lower cistern flanges by means of the long screws P.
Tube T is some mm in length and is supported by the top plate of the cistern C, by corks B, and by a slot not shown in the top of the brass scale housing D. The pressure is then read from scale D using the Vernier. The brass housing is placed once again over the barometer tube and secured to the cistern with the long brass bolts. Kew Pattern barometers should have their scale edge made vertical.
Fortin barometer in A Dictionary of Ecology. 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.
Normally distillation is not necessary. Please note that the information will not be divulged to third parties, or used without your permission. An ivory pin, S, is provided as an index visible through the cistern glass. A portable mercury barometer that was invented in by the French instrument maker Jean Nicholas Fortin — With all the mercury removed, the components of the barometer can be carefully cleaned. This process can be repeated until the barometer tube is empty. NPL’s commercial services are built on years of leadership in accuracy, innovation and scientific research.
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. Setting the vernier 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.
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. Conceptually, it is a simple matter: Air bubbles, moisture and mechanical difficulties all conspire to give a poor result a boarometer which reads too low.
The advantages of this type of barometer are its portability invertedand that it permits the inspection of both free surfaces of mercury whose difference in level have to be measured.
The cistern after removal of the mercury, the barometer tube and the glass cistern tube. The whole is arranged so that it is possible to read the vertical distance between the tip of the ivory pin S and the lower edge of the vernier V.
Figure 1, The anatomy of fortib Fortin Barometer. Refilling the barometer is an operation which requires great care if it is barlmeter be accomplished correctly and the resulting barometer is to read accurately. A glass tube T, about 10mm OD and 6mm ID, is sealed at the upper end and is provided with a tapered lower end which projects into the the cistern C.
Please, subscribe or login to access all content. Mercury barometers have a temperature coefficient of nearly 0. The seal between the cistern glass and the flanges is provided by leather washers.
Arrangement used for filling barometer with a vacuum pump The evacuation is carried ount in stages: 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 foftin the barometer tube T.
The Fortin Barometer was commonly used at meteorological stations to measure atmospheric pressure. The evacuation is carried ount in stages: Lowering the level again will admit a little more air into the barometer tube.
Arrangement used for filling barometer with fkrtin vacuum pump. The cistern and lower section of the baromeeter tube after removal of the barometer tube housing. The Barometer tube should be cleaned with nitric acid using the technique described under Restoring a Fitzroy Barometer. See also fiducial point; Kew barometer. When the setting is correct there should be no more than the slightest dimple where the fiducial point makes contact with the mercury surface.
A vernier scale V is adjustable by the screw Y.
Fortin Barometer | SPM Physics Form 4/Form 5 Revision Notes
If the mercury is to be reused is should be cleaned. More Like This Show all results sharing this subject: The leather lining to the cistern should be treated with particular respect as the surface is relatively easily damaged. To achieve this the mercury surface should first be lowered until it gortin clearly below the fiducial point F.
The barometer is designed to read correctly at 0 deg C.