Measuring and testing – Volumetric content measuring
Patent
1981-02-03
1983-01-25
Swisher, S. Clement
Measuring and testing
Volumetric content measuring
G01F 1700
Patent
active
043696520
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for measuring the volume of solid bodies and to a measuring and/or reference chamber for performing said method.
It is often desired to determine the volume of human beings and animals e.g. for medical control purposes, for determining metabolic effects of food, for determining the merchandise value of animals, etc. in which often the weight should also be determined in order to calculate the specific density on the basis of both said data.
In a known method for determining the volume of bodies there is performed a weighing both in air and under water. With respect to the weighing under water this method is difficult to perform or even completely objectionable in case of e.g. old people, children, patients and many animals.
Accordingly it has been attempted to provide a measurement of the volume of solid bodies that may be carried out more easily by performing the measurement by plethysmometry, i.e. by inserting the body to be measured in a chamber in which the body to be measured is accomodated excluding the chamber from the surroundings, changing the volume of said chamber to a predetermined known extent and measuring the change in pressure caused by said change in volume.
The advantages thereof are that the measurement may be performed by means of a simple apparatus and that in case of human beings and animals the volume of the lungs and other corporal cavities filled with gas are not included in the measurement in as far these cavities are in a more or less free pressure equalizing connection with the exterior of the body. Furthermore the method may well be applied for old people, patients, children and all kinds of animals without any objection.
In plethysmometry there is however the drawback that a relatively quick change in volume not only induces a change in pressure but causes also a change in temperature to an extent not known accurately whereas in case of human beings and animals the object to be measured gives off water vapour and heat causing the measurement to be even less accurate. In order to avoid this drawback as much as is possible one may perform the compression very slowly, while also in case of a quickly performed compression there may be a restoration of the initial temperature so that the pressure will then yield a more proper picture of the volume in view of the isothermal compression thus simulated indirectly, but the longer retention time then required will be uncomfortable for many living beings and will reduce the capacity of the measuring apparatus whereas the heat and water vapour given off will affect more strongly the result of the measurement and even slight leakages from the measuring chamber will have a stronger effect than in case of a short retention time.
The object of the invention is therefore to provide an improvement of said method and more in particular such an improvement that even at a short retention time an accurate measurement of the volume will nevertheless be possible by measuring a change in pressure caused by a change in volume.
According to the invention this object is preferably attained by a method characterized in that the measurement is performed in a chamber like indicated in which apart from the body to be measured at least a major part is filled with a solid filler material having a plurality of interconnected cavities.
It has been found that the compression will occur thereby almost purely isothermally so that a short retention time of e.g. 10 seconds will suffice. Apparently the solid filler material absorbs the heat generated by the compression sufficiently within a normal measuring range due to the very large total surface in the cavities thereof while the filler material shields the body to be measured from the major part of the contents of the chamber such that the emission of heat and water vapour by said body do not affect the measurement unfavourably to a noticeable extent.
For achieving a still higher accuracy the measurement may be performed in a way known in principle by measuring the pressure differe
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patent: 4083228 (1978-04-01), Turner
patent: 4112738 (1978-09-01), Turner
patent: 4184371 (1980-01-01), Brachet
Modern Plastics., 37 (1960.06), 10, 50, article entitled "New Machinery".
Machine Design, vol. 49, No. 2, (1977 01), p. 46.
Machine Design, 32 (1960, 03, 17), 6, 12.
De Rijkslandbouwhogeschool
Swisher S. Clement
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