FR2782556A1 - Pressure measuring device such as liquid filled manometer for domestic use includes adjacent thermometer providing temperature correction of barometer scale - Google Patents

Abstract

The device combines thermometer and barometer to provide accurate pressure measurement. Pressure measuring gauge includes a liquid manometer and a liquid thermometer mounted in such a way as to allow a comparison between the heights of their liquid surfaces. The scales are such that the movement in each column is the same for a given temperature change at constant pressure. Change in pressure is then read by examining the relative difference in level between the two liquid columns. Neither liquid is a toxic liquid. The scales on the two devices may be mounted to slide, in order to facilitate a relative measurement between the two liquid columns.

Description

COMPENSATION PRESSURE MEASURING DEVICE

THERMAL DIRECT READING

  The invention relates to pressure measuring devices, such as pressure gauges, in particular barometers, which preferably do not use mercury. Such barometers

  are sometimes called sympiesometers.

TECHNOLOGICAL BACKGROUND

  Different types of barometers are used in places of residence. The first type is the aneroid barometer which uses a metal bellows which drives an indicator through a conversion mechanism. The other type of barometer is the mercury barometer. Mercury barometers can be made very elegantly, but the use of

  mercury is not recommended due to its toxicity.

  Another type of barometer which does not use mercury is sometimes known by the name of sympiesometer, such as for example the "Tendency barometer" distributed by Denis

  Dingens D.D. Stijlbarometers NV / SA in Bourg-Léopold in Belgium.

  This barometer comprises a volume of gas enclosed in an inverted bulge, which is partially filled with a liquid and is connected to an arm of a pipe in the shape of "U" or "J". A liquid thermometer is placed next to the barometer and the difference in level between the liquid in the thermometer and the liquid in the "U" shaped pipe gives an indication of the atmospheric pressure. The readings can be corrected to a certain extent for temperature variations by the judicious choice of materials and the nature and volume of the gas used. This type of barometer does not require the use of mercury, can therefore be moved more easily and presents a lower risk of pollution of the environment or for human health. However, the barometer is not easy to read, and it

is also not very precise.

  The object of the invention is to provide a pressure measuring device, in particular a pressure gauge or a barometer which gives precise and easy-to-read values and which are compensated for variations in ambient temperature, for

  the gas or liquid pressure measured outside.

  Another object of the invention is to provide a pressure measuring device, in particular a pressure gauge or a barometer, which can avoid the problems of transport and

  toxicity associated with the use of mercury.

STATEMENT OF THE INVENTION

  The invention comprises a thermally compensated pressure measuring device comprising: (A) a liquid pressure gauge and a liquid thermometer, mounted so as to allow a comparison of the height of their liquid surfaces and produced so that the amplitude of movement of the liquid level in the pressure gauge and in the thermometer is substantially equal for a temperature variation at constant pressure of an external fluid, the height of the liquid in the pressure gauge being determined by the compression of a volume of gas at the pressure of the external fluid, and (B) means for a direct reading of the pressure of the external fluid, temperature compensated, starting from the difference between the relative positions of the levels of liquid in the pressure gauge and the thermometer respectively. Both the pressure gauge and the thermometer remain fixed during the

  measurement of the pressure of the external fluid.

  The invention also includes a thermally compensated pressure measuring device comprising: - (A) a liquid manometer and a liquid thermometer, mounted so as to allow a comparison of the height of their liquid surfaces and produced in such a way that the amplitude of the movement of the liquid level in the pressure gauge and in the thermometer is substantially equal for a temperature variation at constant pressure of an external fluid, the height of the liquid in the pressure gauge being determined by compression of a volume of gas at the pressure of the external fluid, and - (B) means for direct reading of the pressure of the external fluid, temperature compensated, starting from the difference of the relative positions of the levels of liquid respectively

  in the pressure gauge and the thermometer.

  The barometer and the thermometer are preferably fixed from

  motionless on a support plate.

  Neither the thermometer nor the manometer preferably includes toxic materials, such as mercury. The direct reading means may comprise a sliding scale with a reference sign, which can be made to slide in alignment with the level of liquid either in the thermometer or in the pressure gauge. This scale can be provided with a graduation in order to read the pressure of the external fluid precisely from the liquid level of the other element, that is to say the pressure gauge or the thermometer. The direct reading means may also include light sensors or pressure sensors, connected to appropriate electronic means and to a display screen and placed so as to deliver output signals related to the height of the liquid in the manometer and respectively the thermometer. The invention also includes a thermally compensated barometer in which the manometer measures atmospheric pressure. Furthermore, the invention also includes other devices for measuring the pressure of a fluid comprising a manometer, such as blood pressure measuring devices, which use an airbag in order to exert pressure on the arm of the person as well as others

  devices for measuring liquid pressure.

  The invention will now be described in more detail at

using the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

  Figure 1 is a schematic elevational view of a barometer according to a first embodiment of the invention. Figure 2 is a schematic elevational view of a rotating and sliding ladder according to another embodiment

for carrying out the invention.

  Figure 3 is a schematic representation of part of a barometer with direct reading according to another

  embodiment of the invention.

  Figure 4 is a schematic representation of part of a barometer with direct reading according to another

  embodiment of the invention.

  DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

  The invention will be described in relation to specific embodiments and drawings, the invention not being limited thereto

  but only by the claims. The invention will be described in

  particular in relation to a barometer, but the invention is not limited to this and relates to any device for measuring the pressure of a fluid comprising a manometer, such as for example a device for measuring the arterial pressure d 'a being

  human, and which must be temperature compensated.

  Figure 1 is a schematic elevational view of a thermal compensation barometer (TCB) 1 according to an embodiment of the invention. The TCB 1 comprises a liquid thermometer 10 and a liquid barometer 20, mounted on a hard support plate and which can be placed side by side so that the liquid surfaces 12 and 22 respectively of the thermometer and the barometer are turned towards the middle of the device. The barometer 20 includes a pressure gauge 21 and a bulge 24 partially filled with a certain volume of gas 28, for example air, nitrogen, argon, neon, helium or another gas appropriate. The pressure gauge 21 is typically attached to the bottom of the bulge 24 and may include a pipe 25 in the shape of a "U" or "J" preferably made of a transparent material having a low coefficient of expansion, such as glass , and which has a narrow opening, typically 1 to 3 mm. The barometer 20 may be provided with air bubbles (not shown) at different locations in the pipe 25. The end 26 of the pipe 25 which is remote from the bulge 24 is open to the atmosphere when the atmospheric pressure is to be measured. Alternatively, it is possible to connect a pressure source of an external fluid to the end 26, for example a pipe which is connected under pressure to the inflatable sleeve of a blood pressure measuring device or to any fluid. appropriate. A portion of the bulge 24 and the pipe 25 are filled with a suitable liquid 27 with a low vapor pressure, typically an oil, for example a silicone liquid such as phenylmethyl siloxane or the like. The liquid 27 preferably has a low vapor pressure, so that it does not evaporate, and which, preferably and to an acceptable extent, does not absorb any moisture or any gas from the atmosphere, or which reacts with it, and which is preferably not toxic or not exceptionally toxic to the environment when the barometer is discarded, or to humans who spend considerable time in the same

space than the barometer.

  The thermometer 10 comprises a bulge 14 and a closed pipe made, preferably, of a transparent material having a low coefficient of thermal expansion, for example glass. A liquid 17 fills the bulge 14 and then flows into the hole of the hollow pipe 15 when the thermometer measures temperatures in an appropriate range, for example between 0 C and 50 C for indoor household barometers. The liquid 17 can be any liquid suitable for a thermometer, for example alcohol. The liquids 17, 27 respectively of the thermometer 10 and the barometer 20 can be colored with suitable dyes, for example aniline dyes,

  preferably non-toxic, so as to make them easily readable.

  As shown in Figure 1, the arm on the inner side of the pipe and the pipe 15 are straight and mutually parallel on the

  greater part of the height of the device.

  At constant atmospheric pressure, differences in temperature cause differences in the level 22 of the liquid 27 in the barometer 20, which are mainly caused by the expansion of the gas 28 in the bulge 24. The variations in level can be determined by the volume and the nature of the gas 28 in the bulge 24, in particular by its coefficient of thermal expansion, and by the nature of the liquid 27, including the vapor pressure of the liquid in the bulge 24 and the coefficient of thermal expansion of this liquid, as well as the coefficient of thermal expansion of the material from which the bulge 24 and the pipe 25 are made and the diameter of the hole in the pipe 25. Similarly, the level variations of the surface 12 of the liquid 17 in the thermometer 10, caused by temperature variations, depend on the coefficient of thermal expansion of the liquid 17 and the material of the bulge 14 and the pipe 15, as well as the diameter of the hole in the pipe 15. By a judicious choice of all these parameters, it is possible to obtain that at constant pressure the variations in height of the surfaces of liquid 12 and 22 respectively of the thermometer 10 and of the barometer 20 are substantially identical for each variation of temperature within a reasonable range. Thus, provided that there is no great difference in atmospheric pressure, the surfaces 12 and 22 of the liquids 17 and 27 respectively in the thermometer 10 and the barometer 20 always remain practically in the same relative position one by

  relative to each other, regardless of the ambient temperature.

  A variation in the relative position of the liquid surfaces 12 and 22 is in this case an indication as to the variation of the atmospheric pressure. This variation of the relative positions of the liquid levels 12 and 22 is a quantitative and substantially linear variation which can be used in order to accurately measure the variation in atmospheric pressure. A means 30 is placed in a suitable position for the direct reading of the atmospheric pressure of level 22 of the

  liquid in barometer 20, which has been temperature compensated.

  This means 30 can be a sliding scale 34, which can be graduated, preferably, in appropriate pressure units, such as millibars or millimeters of mercury. The scale 34 is preferably placed between the thermometer 10 and the arm open to the atmosphere of the barometer 20. The invention is not however limited to this embodiment. The ladder 34 preferably contains a reference sign 32 preferably placed near the thermometer 10 or the barometer 20. The ladder 34 is preferably slidable along a rod 36 in a direction parallel to the pipes 15 and 25 of the thermometer 10 and respectively of the barometer 20. The rod 36 may consist of a bar or other suitable means for guiding the ladder 34 having sufficient friction, so that the ladder 34 is sliding when a force is used , but that it remains fixed when the force is removed. The dimensions of the scale 34 and the other dimensions of the TCB 1 can be selected from

  in order to obtain the desired measurement accuracy.

  In order to calibrate the TCB 1 at the origin, the barometer 20 and the thermometer 10 are placed in an atmosphere having a known or standard pressure. The reference sign 32 of the scale 34 is brought to the level of one of the liquid levels 12, 22 of the liquids 17, 27 by the sliding of the scale 34 along the rod 36. The level of the another level of liquid 22, 12 of liquids 27, 17 is noted and the known pressure reported on the scale 34. This calibration process is repeated for different known or standard pressures. After calibration, the scale 34 contains calibrated signs and interspersed signs

  from which each atmospheric pressure can be read.

  For the use of the TCB 1 at different altitudes, it may be necessary to use different calibrations of the scale 34. A plurality of scales 34 can be provided for the TCB 1, so that the TCB 1 can be adapted by the buyer at the altitude of his situation by determining the exact scale 34 appropriate on the device. For extreme altitudes, the TCB 1 is preferably made so as to operate precisely at

such altitudes.

  When in operation, the reference sign 32 on the scale 34 is brought to one of the corresponding liquid levels 12 or 22 by the sliding of the scale 34 along the rod 36. Then, the atmospheric pressure is read directly on the scale 34 from the position of the other liquid level 22, 12, without having to refer to other scales or diagrams. The

  temperature can also be read from thermometer 10.

  As shown in FIG. 1, the scale 34 is moved so that the reference point 32 is at the same height as the level 12 of the liquid in the thermometer 10. The pressure is then read directly on the scale 34 at the location 22 of the liquid in the barometer 20. For a TCB 1 device of about one meter in height, the scale 34 can be made so that it has a length of 25 cm from the point where atmospheric pressure can be read easily with a

accuracy of 0.5 millibar.

  Figure 2 is a schematic representation of a scale 34 according to another embodiment of the invention. Several pressure scales 31 are arranged on a cylindrical piece 34 which is both pivoting and sliding in length.

  along the rod 36. Each scale 31 is suitable for (that is to say

  say precise for) a determined range of altitudes and the purchaser of the apparatus turns the cylinder 34 to the desired scale 31 along the barometer 20 or the thermometer 10. There is provided a reference sign or another structure 32 at an appropriate position of the cylinder 34 in order to place the cylinder 34 on the rod 36 relative to one of the liquid levels 12, 22 respectively of the thermometer 10 or the barometer 20 in order to read the atmospheric pressure. The direct reading means 30 of atmospheric pressure according to the present invention can also give a digital or analog reading. As shown schematically in FIG. 3, for example, several light sensors 38 can be placed over an appropriate length and on the side remote from the thermometer and the barometer 10, 20 from a light source. The light sensors 38 are placed in such a way that the general lighting of a room for example casts a shadow of the liquid 17, 27 respectively from the thermometer 10 and the barometer 20 on the light sensors 38. Appropriate electronic reading means 37 regularly scan the light sensors 38 in order to determine the position at which the shadow of the liquid 17, 27 is cast on the light sensors 38. Reading the light sensors gives an indication of the height of the liquid levels 12, 22 respectively in the thermometer and the barometer, 20. The atmospheric pressure can be calculated from the difference of these values, by the use of appropriate electronic processing means 37 and be represented on an appropriate analog or digital display device. 39. For example, a standard 1024-element CCD photosensor array can be used for light sensors 38. Pou r measure a maximum pressure variation of 75 millibars (for example between 975 and 1050 millibars), a display of the pressure measurements is obtained with an accuracy of 0.14 millibar, which

  is more than enough for normal household use.

  The direct reading means 30 according to the invention can also be provided by pressure sensors 41, 42 as shown diagrammatically in FIG. 4. At the base of the appropriate parts of the pipes 15, 25 respectively of the thermometer and the barometer 10,20 there is a pressure sensor 41 in liquid contact with the liquid 17 of the thermometer 10 and a pressure sensor 42 is in liquid contact with the liquid 27 of the barometer 20. These pressure sensors 41, 42 are low pressure sensors capable of give an accurate reading of the liquid heights in the thermometer 10 and the barometer 20 respectively. Such low pressure sensors can be obtained from Vega Griesshaber KG in Germany. The output of the pressure sensors 41, 42 is connected to suitable electronic means 37. When the output of the pressure sensors 41, 42 consists of analog values, these can be converted into digital values by means of analog-to-digital converters in electronic means 37. These values are indicative as to the height of the liquid in the thermometer 10 or the barometer 20. By calculating the difference in height between the liquids in the thermometer 10 and the barometer 20, it is possible to determine atmospheric pressure and reproducing it on an appropriate analog or digital display device 39. By the arrangement of pressure sensors 41, 42 behind the barometer 20 and the thermometer 10 or else inside the element the largest of the barometer 20 and the thermometer, these sensors 41, 42 can be hidden from view and they do not

  not disturb the generally elegant appearance of the TCB 1.

  The invention is described using specific embodiments and figures, but those skilled in the art will understand that modifications and additions to the invention, which remain within the scope of the invention as defined in the

  appended claims can be made. For example, the

  thermometer and manometer were shown with relatively straight arms, scale 34 moving linearly relative thereto, but the invention is not limited to this and variations in the shape of the barometer and the thermometer are not intended to modify the nature of the invention. For example, both the thermometer and the pressure gauge could be provided with curved arms evolving in parallel and the scale 34 would then be sliding along a curved trajectory which

  would follow that of the pressure gauge and the thermometer.

  Furthermore, the invention includes any pressure measuring device based on a pressure gauge. The end 26 of the pressure gauge 21 can be connected to any source of gas pressure or of liquid pressure, provided that this liquid is immiscible with the liquid 27 of the pressure gauge 21. In particular, the invention also comprises using the following pressure gauge 21

  the invention with a thermometer 10 for thermally compensated measurement of human blood pressure. In this case, the gas present in the inflatable sleeve 5 placed around the arm of the person whose pressure is measured is connected to the end 26 of the barometer 20.

Claims (11)

  1. A thermally compensated pressure measuring device comprising: (A) a liquid manometer and a liquid thermometer, mounted so as to allow a comparison of the height of their liquid surfaces and produced so that the amplitude of the movement the level of liquid in the pressure gauge and in the thermometer is substantially equal for a temperature variation at constant pressure of an external fluid, the height of the liquid in the pressure gauge being determined by the compression of a volume of gas at the pressure of the external fluid, and (B) means for reading the pressure of the external fluid, temperature compensated, starting from the difference between the relative positions of the liquid levels respectively   in the pressure gauge and the thermometer.   2. thermally compensated pressure measuring device according to claim 1, characterized in that the means   reading devices (B) are direct reading means.   3. Thermally compensated pressure measuring device   according to one of claims I and 2, wherein both the   pressure gauge that the thermometer are fixed immobile on a support plate.   4. Thermally compensated pressure measurement device   according to one of claims 1 to 3, wherein neither the   thermometer, nor the manometer contains toxic materials such as mercury.   5. Pressure compensation device with thermal compensation   according to one of claims 1 to 4, in which the means for   readings contain a sliding scale with a reference sign, which can be slidably brought on a line with the liquid level in the thermometer or with the liquid level in the pressure gauge, the scale being graduated so that the pressure of the external fluid can be read from   liquid level of the thermometer or pressure gauge.   6. A thermally compensated pressure measuring device according to claim 5, wherein the scale slides on a rod. 7. Pressure compensation device with thermal compensation   according to one of claims 1 to 6, in which the means for   readings contain a series of scales, each scale being suitable for a determined range of altitudes and being graduated so that the pressure of the external fluid can be read at   from the liquid level of the thermometer or pressure gauge.   8. Thermally compensated pressure measuring device   according to one of claims 1 to 7, in which the pressure gauge   contains a bulge partially filled with gas and a hose   "J" or "U" shaped on the lower side of the bulge.   9. A thermally compensated pressure measuring device according to claim 8, in which the pipe in the form of "J" or   "U" is next to and in parallel with the thermometer.   10. A thermally compensated pressure measuring device according to one of claims 1 to 9, in which the means for   reading are placed between Ir thermometer and barometer.   11. thermally compensated pressure measuring device according to one of claims 1 to 10, in which this device   pressure measurement is a barometer.