Aneroid Barometers Research Articles

An equation for the ‘weather glass’

The ‘weather glass’, containing air and (usually) water, is a compact barometer, less accurate but more convenient than the Torricellian barometer of 1644. The weather glass pre-dates the Torricellian barometer, and coexisted with it until it was out-competed from about 1860 by the more accurate, comparably compact aneroid barometer. Today, the weather glass is sold as an elegant interior decoration and is also constructible in a student laboratory. Elementary physics allows one to model its response to changing pressure at constant temperature and also the adjustments that need to be made if the temperature varies. In an air- and water-containing weather glass, the principal factor affecting movements of the water level is the expansion and contraction of the atmospheric nitrogen, oxygen, and argon in a headspace above the water, well represented by the ideal gas law. The water acts primarily as a piston allowing the expansion and contraction to be observed. In contrast, Torricellian and aneroid barometers respond directly to the pressure difference between the atmosphere and a vacuum.

Implementation of Fuzzy Logic Controller for Pressure Sensor Calibration Chamber

Atmospheric pressure is a weather element that must be observed in the field of meteorology. Electronic barometers, aneroid barometers, mercury barometers are generally instruments for atmospheric pressure measurement. The barometer must be calibrated periodically to ensure the performance of the instrument. To achieve the best target uncertainty during calibration, besides using an accurate primary standard barometer, a stable pressure controller is also needed. Pressure calibration media using a pressurised test chamber is more beneficial due to its capability to accommodate all types of pressure sensors. However, pressurise test chamber still requires an operator to control and stabilise pressure inside the test chamber. In this study, fuzzy logic has been programmed into a microcontroller to control the solenoid valve and vacuum pump for regulating air pressure inside a pressurised test chamber automatically. Fuzzy logic changes the solenoid valve states periodically by varying the opening and closing times. The final result of this study is a comparison between the calibration results using pressure controller with fuzzy logic and without fuzzy logic with the same primary standard and unit under test. The result of expanded uncertainty without a fuzzy logic controller is 13.06 hectopascal. Meanwhile, the pressure calibration process using fuzzy logic to control pressure in pressurised test chamber achieve 0.09 hectopascal of expanded uncertainty in 1000 hectopascal pressure value with coverage factor, k=2, and confidence level of no less than 95 %.

On the Meteorological Instruments and Observations Made during the 19th Century Exploration of the Canadian Northwest Passage

Meteorological records from about 30 British Navy ships that overwintered in the Canadian Arctic islands between 1818 and 1859 are the earliest detailed baseline of direct historical data in this region against which modern and future climate trends can be assessed. We describe the types of meteorological instruments and the observational methods employed aboard these ships. For measuring air temperatures, both mercurial and spirit thermometers were used. Observations of atmospheric pressure were made using marine and aneroid barometers. Wind direction and speed were also logged. The Royal Navy’s ordered and disciplined daily regime was well-suited to regular scientific observations. Individual instruments on most Navy ships were calibrated against established Royal Observatory standards before and after expeditions. Many recording officers commented on the relative unreliability of spirit thermometers below the freezing point of mercury. Little contemporary written evidence exists regarding absolute accuracy or precision of meteorological instruments taken to the Arctic, but some calibration data are available to assess typical instrument errors between 32° and −38°F (0° and −39°C). Our comparison of minimum daily temperatures from four overwintering ships in 1853 and 1854 shows very high correlation coefficients. The mutual consistency of these records implies good instrumental precision. Although the absolute accuracy of temperatures recorded below the freezing point of mercury is in doubt, those above this point are relatively accurate. Guidance on the preferred methods of observing and recording were codified in, for example, the Admiralty’s Manual of Scientific Enquiry (Herschel, 1851). Meteorological registers were regarded as official documents that were, as far as possible, required to be complete and no attempt was to be made to fill in missing data. The need to screen or cover instruments from both solar and terrestrial radiation was also recognized from the earliest expeditions. It was not until the 1850s that standardizing the exposure of thermometers was resolved through the introduction of louvered screens. This unique set of ships’ meteorological registers presents opportunities to investigate a variety of meteorological parameters for the Canadian High Arctic in the 19th century, allowing quantitative assessment of change relative to contemporary climate.

Back to basics: The ‘met. enclosure’: Part 8(b) –Barometric pressure, aneroid barometers

WeatherVolume 57, Issue 6 p. 204-209 Research Article Back to basics: The ‘met. enclosure’: Part 8(b) –Barometric pressure, aneroid barometers Ian Strangeways, Corresponding Author Ian Strangeways TerraData, WallingfordTerra-Data, PO Box 48, Wallingford, Oxon. OX10 0JJ.Search for more papers by this author Ian Strangeways, Corresponding Author Ian Strangeways TerraData, WallingfordTerra-Data, PO Box 48, Wallingford, Oxon. OX10 0JJ.Search for more papers by this author First published: 29 December 2006 https://doi.org/10.1256/004316502760053558Citations: 10AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume57, Issue6June 2002Pages 204-209 RelatedInformation

Effect of preloading on creep resistance in bending of a strip of bronze BrBNT1, 9Mg

1. On the creep curve of specimens, like on the creep curve of aneroid barometers, we can distinguish two stages: nonsteady and steady-state creep. 2. Producing a field of residual deformations in the specimens by means of preliminary loading makes it possible to reduce the creep rate at the steady-state stage. 3. The greater the residual deformation at the initial loading is, the lower is the creep rate at its steady-state stage. 4. With rising test temperature the steady-state creep rate somewhat increases, and when σo increases, it decreases. 5. Increased creep stress σc with the same initial residual stress σo leads to increased steady-state creep rate.

A NEW METHOD FOR ASSESSING THE ATMOSPHERIC REFRACTIVITY CORRECTION IN OPTICAL EDM

Abstract The atmospheric refractivity correction in EDM is usually derived from on site measurements of the ambient temperature and pressure. The purpose of this short paper is to demonstrate that a small bellows, similar to those used in aneroid barometers, when filled with a dry “ideal” gas can be used to derive the correction directly.

CHARTS FOR THE REDUCTION OF HEIGHTS FROM ANEROID READINGS BASED ON A STANDARD ATMOSPHERE AND A STANDARD LAPSE-RATE

Atmospheric pressure at a given point is measured by the weight of the vertical column of air on a uniform cross section above that point, which again depends on the density and chemical composition of the air and also on the temperature and the gravity value throughout the air column. The humidity is deduced from simultaneous readings of both wet and dry bulb thermometers and the air temperature is known from the dry bulb thermometer readings. Since the thermometer readings are obtainable only at the points of observation, some assumptions with regard to the temperature distribution in the air column are necessary for an accurate estimation of heights. The methods generally used for the reduction of aneroid readings are thus based on two assumptions—the isothermal and the lapse-rate. According to the isothermal assumption the temperature of the air column is considered uniform throughout. But this is contrary to observed facts; for normally up to a certain limiting height the telnperature of the air is observed to fall with increase of height at a more or less constant rate. The assumption of a standard lapse-rate does on the other hand conform more closely to nature and has therefore been now in general use. The relevant “Aneroid Tables Based on a Standard Atmosphere and a Standard Lapse-Rate” by H.M.S.O. provide an accurate and straightforward computation. But the main defect with these elaborate tables, as rightly indicated by Col. D. R. Crone in his article on “Heights by Aneroid Barometers” (E.S.R. ix, 69, 311–317),is that “these are not well suited for rapid entry and the method of correction for observed humidities with the wet and dry bulb is fiddling and not suited for mass reduction of readings”. Moreover, the tables are also defective in the sensethat they give rise to errors which become appreciable when dealing with higher altitudes.

CHARTS FOR THE REDUCTION OF HEIGHTS FROM ANEROID READINGS BASED ON A STANDARD ATMOSPHERE AND A STANDARD LAPSE-RATE

Atmospheric pressure at a given point is measured by the weight of the vertical column of air on a uniform cross section above that point, which again depends on the density and chemical composition of the air and also on the temperature and the gravity value throughout the air column. The humidity is deduced from simultaneous readings of both wet and dry bulb thermometers and the air temperature is known from the dry bulb thermometer readings. Since the thermometer readings are obtainable only at the points of observation, some assumptions with regard to the temperature distribution in the air column are necessary for an accurate estimation of heights. The methods generally used for the reduction of aneroid readings are thus based on two assumptions—the isothermal and the lapse-rate. According to the isothermal assumption the temperature of the air column is considered uniform throughout. But this is contrary to observed facts; for normally up to a certain limiting height the telnperature of the air is observed to fall with increase of height at a more or less constant rate. The assumption of a standard lapse-rate does on the other hand conform more closely to nature and has therefore been now in general use. The relevant “Aneroid Tables Based on a Standard Atmosphere and a Standard Lapse-Rate” by H.M.S.O. provide an accurate and straightforward computation. But the main defect with these elaborate tables, as rightly indicated by Col. D. R. Crone in his article on “Heights by Aneroid Barometers” (E.S.R. ix, 69, 311–317),is that “these are not well suited for rapid entry and the method of correction for observed humidities with the wet and dry bulb is fiddling and not suited for mass reduction of readings”. Moreover, the tables are also defective in the sensethat they give rise to errors which become appreciable when dealing with higher altitudes.

Barometric levelling and cargography of equatorial regions

Photogrammetry as applied to the establishment of colonial maps on medium scales (1 : 25.000 – 1 : 50.000) includes aerial triangulation and aerial levelling. Planimetric ground control can be provided by geodetic triangulation or by a limited number of oriented baselines, the longitudinal deformations of the strips being regular. Altimetric ground control on the other hand must be relatively dense especially in view of the transversal torsion of the strips, which is generally irregular. Therefore it is necessary to determine the heights of a relatively large number of ground control points situated outside the axis of each strip. These heights can be determined easily by barometric levelling. A new accurate aneroid barometer, designed by the author is described. It consists of a column of seven metal boxes C1, C2 … (fig. 1, page 25 fig. 2, page 26) whose deformations add together. The movements of the surface of the upper box, due to changes of atmospheric pressure are not — as in ordinary aneroid barometers — magnified by a system of levers, but observed directly by optical means. A wire F1(fig. 2.) whose movements are identical with those of the surface of the upper box, is observed by a 14 power microscope M.C. (fig. 2) or H1H2 (fig. 1). A fixed wire F2 is observed simultaneously. The variation of the distance between these wires is measured by means of an eyepiece micrometer M, estimating 0,001 mm. A thermometer permits the measurement of the temeprature of the compartment which contains the metal boxes. The whole is mounted on rubber cushions in a wooden case. The case is suspended fibration free from a metallic frame by means of rubber tubes. (fig. 3). A description is given of trials carried out in Belgium. The instrumental constant was determined each day by measuring three datum stations. The atmospheric pressure at these points was measured during the day every ten minutes by means of mercury barometers and reduced to 20° temperature. (fig. 4, 5 and 6, pages 29–30). The tables T1, T2 and T3 (pages 32–34) fourth column show the altitudes measured with the new barometer at a number of points. The fifth column gives the differences between these results and the geodetic altitudes. These differences are affected by a systematic error, caused by the general change in atmospheric pressure in the area concerned. This change is represented by straight lines in fig. 4, 5 and 6, indicating sections at time AB, BC and CD. The systematic error mentioned was eliminated by computing the mean of the differences per section and subtracting it from each difference. The adjusted differences thus obtained are shown in the seventh column of the tables T1, T2 and T3. Their mean value E (written at the bottom) is a function of e1, e2 and e3: E = e12 + e22 + e32 in which: e1 is the mean error of the pressure measured at a datum station e2 is the mean error of the pressure measured at the other points e3 is the mean error caused by slope of the pressure level. e1 was computed by comparing the measurements at the three datum stations, to give e1 = 0,4 m. The error e3 is assumed to be a linear function of the fluctuation of the pressure observed at the datum stations, with respect to the straight lines AB, BC and CD (fig. 4, 5 and 6). These fluctuations are: June 3: 0,8 m whence e1 = 0,8 k June 5: 0,7 m whence e1 = 0,7 k June 7: 1,1 m whence e1 = 1,1 k Substitution of these values in the above equation gives three equations, the solution of which by the method of least squares gives the internal mean error of the instrument: e3 = 0,4 m In equatorial regions the mean error e3 would be negligible. Assuming a datum station provided with two barometers of the type described and four carried to the other points, the mean error of the altitude may be estimated at 0,2 m.

Barometric levelling and cargography of equatorial regions

Photogrammetry as applied to the establishment of colonial maps on medium scales (1 : 25.000 – 1 : 50.000) includes aerial triangulation and aerial levelling. Planimetric ground control can be provided by geodetic triangulation or by a limited number of oriented baselines, the longitudinal deformations of the strips being regular. Altimetric ground control on the other hand must be relatively dense especially in view of the transversal torsion of the strips, which is generally irregular. Therefore it is necessary to determine the heights of a relatively large number of ground control points situated outside the axis of each strip. These heights can be determined easily by barometric levelling. A new accurate aneroid barometer, designed by the author is described. It consists of a column of seven metal boxes C 1 , C 2 … (fig. 1, page 25 fig. 2, page 26) whose deformations add together. The movements of the surface of the upper box, due to changes of atmospheric pressure are not — as in ordinary aneroid barometers — magnified by a system of levers, but observed directly by optical means. A wire F 1 (fig. 2.) whose movements are identical with those of the surface of the upper box, is observed by a 14 power microscope M.C. (fig. 2) or H 1 H 2 (fig. 1). A fixed wire F 2 is observed simultaneously. The variation of the distance between these wires is measured by means of an eyepiece micrometer M , estimating 0,001 mm. A thermometer permits the measurement of the temeprature of the compartment which contains the metal boxes. The whole is mounted on rubber cushions in a wooden case. The case is suspended fibration free from a metallic frame by means of rubber tubes. (fig. 3). A description is given of trials carried out in Belgium. The instrumental constant was determined each day by measuring three datum stations. The atmospheric pressure at these points was measured during the day every ten minutes by means of mercury barometers and reduced to 20° temperature. (fig. 4, 5 and 6, pages 29–30). The tables T 1 , T 2 and T 3 (pages 32–34) fourth column show the altitudes measured with the new barometer at a number of points. The fifth column gives the differences between these results and the geodetic altitudes. These differences are affected by a systematic error, caused by the general change in atmospheric pressure in the area concerned. This change is represented by straight lines in fig. 4, 5 and 6, indicating sections at time AB, BC and CD . The systematic error mentioned was eliminated by computing the mean of the differences per section and subtracting it from each difference. The adjusted differences thus obtained are shown in the seventh column of the tables T 1 , T 2 and T 3 . Their mean value E (written at the bottom) is a function of e 1 , e 2 and e 3 : E = e 1 2 + e 2 2 + e 3 2 in which: e 1 is the mean error of the pressure measured at a datum station e 2 is the mean error of the pressure measured at the other points e 3 is the mean error caused by slope of the pressure level. e 1 was computed by comparing the measurements at the three datum stations, to give e 1 = 0,4 m. The error e 3 is assumed to be a linear function of the fluctuation of the pressure observed at the datum stations, with respect to the straight lines AB, BC and CD (fig. 4, 5 and 6). These fluctuations are: June 3: 0,8 m whence e 1 = 0,8 k June 5: 0,7 m whence e 1 = 0,7 k June 7: 1,1 m whence e 1 = 1,1 k Substitution of these values in the above equation gives three equations, the solution of which by the method of least squares gives the internal mean error of the instrument: e 3 = 0,4 m In equatorial regions the mean error e 3 would be negligible. Assuming a datum station provided with two barometers of the type described and four carried to the other points, the mean error of the altitude may be estimated at 0,2 m.

A First Book of Meteorology

MR. A. J. STARR's little book is a useful introduction to weather study, well illustrated and, on the whole, clearly written. It opens with a description of the composition, pressure and temperature of the atmosphere, and of the principles of mercury and aneroid barometers, though the description of the aneroid is rather confused. The next chapter deals with wind, including the Beaufort scale, but there is no mention of gustiness ; a photograph of the record from a pressure-tube anemometer would have been a useful addition. The chapter on clouds is well illustrated by photographs ; those on weather and visibility call for no comment. Then follows a short account of observations and measurements, with some rather crude descriptions of instruments. As the Fortin and Kew barometers are mentioned by name, it might have been worth while to explain briefly the difference between them, and a simple illustration of a vernier would have been useful. More serious is the complete omission of any reference to maximum and minimum thermometers ; although a table of frost-days is included, no indication is given of how they are defined, and the reader is left to infer that a frost-day is one with a deposit of hoar-frost. This section might have been expanded at the expense of some of the information about the synoptic code and plotting, which is of less direct interest to the beginner. The chapters on pressure systems and weather forecasting are good and useful.

HEIGHTS BY ANEROID BAROMETER

Of all methods of surveying, the provision of heights by means of aneroid barometers probably arouses the greatest variety of emotions in the practical surveyor. Some pack a single aneroid rather shamefacedly, look at it only when in difficulties and are thankful if its reading is within 200 feet of what they expect; others with as little care, expect readings correct to the smallest division of the scale; whilst at the other end of the scale are the devotees of the aneroid who will attempt-and often succeed-in raying out gravity pipe lines in flattish country with no other instruments.

Ultimate Precision of Barometric Surveying

By constructing two aneroid barometers which could be compared with an instrumental precision equivalent to 0.3 foot of elevation difference, it was possible to obtain a measure of the errors of barometric surveying which originate solely from atmospheric disturbances. It was found that in fairly level country, under average weather conditions, the contribution of atmospheric disturbance to the probable error of a single elevation observation is 0.96 foot when two aneroids are 3 miles apart. Practical applications and methods of carrying out elevation surveys are discussed.

Digests of Papers on Aircraft Operations

Use of Barometric Pressure for Setting Sensitive Altimeters in Airport and Airivay Traffic Control. The increasing complexity of the problems involved in the control of airport and airway traffic has necessitated the adoption of a uniform scheme for the setting of sensitive altimeters throughout the country. This scheme, following the proposals of the Weather Bureau at a Conference on Airport and Airway Traffic Control held on November 12-14, 1935, under the auspices of the Bureau of Air Commerce, Department of Commerce, contemplates the use of the pressure measuring instruments employed in the airway weather service (both mercurial and aneroid barometers) for the purpose of obtaining pressure settings pertinent to the various airports, such that if a sensitive (Kollsman) altimeter in an airplane is set accordingly, the airplane can land at an airport to which the setting pertains just as the altimeter hands indicate the surveyed elevation of the landing field above sea level. In this paper the details of the above-mentioned proposals are presented. It is first to be pointed out that, assuming radio communication between an observer at the ground and the pilot in the airplane, the use of sensitive altimeters in blind landing and blind cross-country flying presents four distinct problems: (1) the determination of the barometric pressure at the level of the altimeter when the airplane is just at the point of landing on the ground, (2) the precise calibration of the altimeter in accordance with the Standard Atmosphere relation of pressure to height, (3) the determination (or the knowledge) of the elevation of the terrain above sea level in the general neighborhood of the airplane and with reference thereto, and (4) the determination of the mean temperature of the air column between the airplane and the ground beneath. In regard to the determination of barometric pressure near the ground, it is shown that the mercurial barometer is generally superior both to the aneroid barometer and to the altimeter owing to its greater precision, stability and relative freedom from the various errors inherent in instruments which depend for their indications on the expansion or contraction with change of air pressure of evacuated diaphragm capsules or similar devices. The mercurial barometer thus forms a more suitable standard than either of the other instruments. The aneroid barometer when used in conjunction with a mercurial barometer is found to be advantageous for the purpose of obtaining the desired results expeditiously during intervals intermediate between the times when the readings of the former instrument are compared with the readings of the latter and corrections to the aneroid are thus obtained. The pressure measuring equipment involved here is already available at a number of stations in the airway weather reporting service. It is pointed out that with the maintenance of the customary precision employed in the calibration of sensitive altimeters, the procedure under consideration which involves the use of this equipment may be conveniently applied to the checking of altimeters in the field. This is seen to provide an important advantage over the methods hitherto used. The fundamental mechanical characteristic of the sensitive altimeter is then outlined, viz., that given an appropriate setting therefor, an altimeter can be made to indicate any preassigned altitude reading when brought to a given air pressure, and thence it is shown how the desired setting may be easily determined with the aid of the Standard Atmosphere tables once the air pressure just above a landing field is known and an altitude is preassigned thereto. It is demonstrated that for the sake of speed in procedure it is best to prepare a table of these settings in advance using as the sole argument the air pressure just above the field at the average level of altimeters in landing airplane, viz., about 8 feet.

Experiments on aneroid barometers at Kew observatory and their discussion

The paper deals with two species of data. The first consists of articulars derived from the records at Kew Observatory as to errors observed in about 300 aneroid barometers. These had been objected to the ordinary Kew test, which consists in lowering the ressure to which the aneroid is exposed inch by inch to the lowest oint at which verification is desired, and raising the pressure in a corresponding way to its original value.

XI. Experiments on aneroid barometers at kew observatory, and their discussion

§ 1. The ordinary aneroid barometer is an instrument whose chief recommendations are its portability and the ease with which it can be used by travellers. It is essentially a field instrument, and it would be largely waste of time to treat it as if intended for the laboratory. The first object of the present investigation is to acquire knowledge likely to increase the usefulness of the aneroid under the conditions in which it is actually employed.

Diary of Societies

THURSDAY, JUNE 9. ROYAL SOCIETY, at 4.30.—On a New Constituent of Atmospheric Air: Prof. W. Ramsay, F.R.S., and Morris H. Travers.—Experiments on Aneroid Barometers at Kew Observatory and their Discussion: Dr. C. Chree, F.R.S.—The Nature of the Antagonism between Toxins and Anti-Toxins: Dr. C. J. Martin and Dr. T. Cherry.—Some Differences in the Behaviour of Real Fluids from that of the Mathematical Perfect Fluid: A. Mallock.—On the Heat Dissipated by a Platinum Surface at High Temperatures: J. E. Petavel.

Our Astronomical Column

FINDER·CIRCLES FOR EQUATORIALS.—A very ingeniousand what may prove a most useful addition to an equatorial are the so-called star-dials or finding-circles, a brief account of which is contributed to the current number of the Zeitschrift für Instrumentenkunde (4 Heft, April 1894). Every worker with the equatorial will no doubt at some time have found out that the present mode of setting the instrument on some object, as, for instance, a star, is not always very convenient, and in addition employs comparatively far too much time. The object of these finding-circles 15 to reduce this time very considerably, and a use of three years has shown that its aim has been successfully attained. The instrument to which it has been applied is the 12-inch of Georgetown College Observatory, Washington. On the pillar of this instrument are the two hand-wheels, by means of which the telescope is moved in right ascension and declination, and also two microscopes for reading the R.A. circle. Both axes of the telescope carry the usual circles for orientation, each being graduated in fine divisions on silver and large white divisions on a dark background. The finding-circles are situated just above the hand-wheels mentioned above, and fixed to the pillar, looking like a pair of aneroid barometers or steam gauges; they are arranged as follows:—The circular divided disc, with the declination divisions arranged round its circumference, is fixed firm in its case, and the index is so geared to the telescope that any movement of the latter is recorded on the dial; this gives one directly the declination. In the case of the other dial, that for right ascension, the disc is divided into two circles of twelve hours each, and instead of being fixed is moved by clockwork, sidereal time being shown on its face by means of another index; this latter index responds also to the movement of the telescope, but is quite independent of the first one. It will at once be seen that with these two dials so conveniently placed the telescope can be at once oriented, while the question of hour-angle is entirely eliminated.

An improvement in aneroid barometers

An improvement in aneroid barometers

XV. An account of certain experiments, on aneroid barometers, made at Kew Observatory, at the expense of the Meteorological Committee

In judging of the value of an instrument, such as an aneroid, it is not the mere extent of difference between its indications and those of a standard barometer that ought to guide us; but it is rather the constancy of its indications under the various circumstances to which it may be subjected, that determines its value. An aneroid may differ from a standard barometer at the ordinary pressure, and to a greater extent at other pressures; but provided these differences can be well ascertained and remain constant, such an instrument ought to be regarded as valuable, just as much as a chronometer of known constancy, but of which the rate is wrong.