EP1252485A1

EP1252485A1 - Method for measuring the volume of an object and an arrangement therefor

Info

Publication number: EP1252485A1
Application number: EP00987878A
Authority: EP
Inventors: Peter Ivar Wide
Original assignee: Cerealia R& D AB
Current assignee: Cerealia R& D AB
Priority date: 1999-12-21
Filing date: 2000-12-11
Publication date: 2002-10-30
Also published as: AU2415101A; SE517191C2; WO2001046652A1; SE9904690D0; SE9904690L

Abstract

The present invention relates to a method and an arrangement for measuring the volume (1') of a bread object (1) placed in a defined space (2), the volume (2') of the defined space being chosen greater than the volume (1') of the bread object, wherein information representing the volume of the space when empty, and information representing the volume of the space reduced by the presence of the object constitute measurements enabling determination of the volume of the bread object. A single pressure source (4) adapted for a compressible gas or gas mixture is connected, via a common space (5), to said defined space (2) and also to a space (3) serving as reference, said spaces (2, 3) being identical. Each of said two spaces (2, 3) is connected individually to a sensor (6) for determining pressure differences, and a means (7) is utilised for evaluating the volume (1') of the bread object (1) on the basis of the information from said sensor (6).

Description

METHOD FOR MEASURING THE VOLUME OF AN OBJECTANDAN ARRANGEMENTTHEREFOR

Technical field The present invention relates generally to a method for measuring the volume corresponding to the exterior of an object placed in a space defining the object.

The volume of the defined space should be chosen somewhat greater than the volume of the object. The invention also relates to an arrangement for measuring the volume of an object, primarily in accordance with the significant features of the method.

The method and the arrangement are based on having access to a first item of information representing the empty volume of a defining space and a second item of information representing the volume of the space reduced by the presence of the object. These items of information shall, preferably directly, constitute measurements enabling determination of the volume of the object.

The invention is based on the known principle that when a defined space having specific volume and specific pressure is supplied for a period of time with a specific quantity of compressible gas or gas mixture, such as air, the gas pressure increases with the time inside the space and if the quantity of gas supplied is the same but the volume inside the space is less, e.g. due to the presence of an object, the gas pressure will increase more quickly with the time inside the latter space.

It should also be noted that the method has been developed primarily in order to measure the volume of a ready-baked product or object in the form of a loaf of bread, without spoiling the bread.

It should be observed that although the following description covers measurement of a volume, the density of the object can also be determined by utilising a weighing device, thereby determining the weight of the object.

Background art

Methods for measuring the volume of bread, based on the above known principle, are already known. As regards measuring the volume of one or more loaves of bread, it may be mentioned that a method and means are already known through Swedish patent SE-C2-504 557 for measuring the volume of a ready-baked loaf of bread.

This shows the possibility of utilising an ultrasonic transmitter (10) for a plurality of distance measurements throughout the measuring process, oriented to enable evaluation of a specific distance to a known reference point (R) in the bread.

A relative movement is created between the bread (2) and the ultrasonic transmitter (10) so that substantially the entire surface of the bread (2) is succes- sively encountered by a measurement signal from the ultrasonic transmitter (10) during the relative movement.

Since the distance between the ultrasonic transmitter (10) and the reference point (R) is known, the distance from the reference point (R) to a number of measuring points on the surface of the bread can be calculated with the aid of the distances measured by the ultrasonic transmitter (10).

A partial volume for the bread is determined for each measured distance from the reference point (R) to the surface of the bread, and the total volume of the bread is determined by adding all the partial volumes.

Other methods, besides the method and means described above, have also been proposed for measuring the volume of a ready-baked loaf of bread.

In all industrial bread baking processes the quality of the raw materials, particularly the flour, used in the baking process is decisive to the baking result.

A method frequently used for measuring the actual quality of the flour used is to bake bread in accordance with a standardised baking test, e.g. a test authorised by the American Association of Cereal Chemists or by the International Association for Science and Technology, and thereafter measure the volume of the ready-baked bread.

The bread volume is often determined by placing the bread in a container having known volume and then filling the container with a calibrated quantity of rape or poppy seeds that are allowed to surround the bread. The volume of the bread is then read on a scale on the container, which is graded as a function of the volume of the container and the calibrated quantity of seeds.

Obviously this method of measuring the volume of bread has a number of drawbacks. The measurement is performed entirely manually. It is time-consum- ing and complicated. The quantity of seeds must be calibrated at regular intervals since the seeds often get caught in small cavities in the outer structure of the bread and are removed from the container with the bread. Furthermore, the method lacks accuracy. If the container is shaken during the measurement, for instance, the rape seeds will be packed more tightly, thereby reducing the volume. The volume of the container must also be adjusted to the size of the bread in order to achieve satisfactory accuracy. Several different arrangements may therefore be required. Patent publication FR-A-2 544 072 shows an alternative method of meas- uring the volume of bread, according to which a loaf of bread is placed on a rotating table and illuminated from behind.

A camera records a silhouette picture of the bread from a point diametrically opposite to the point from which the bread is illuminated. The bread is then turned and the measurement repeated for a number of different angles. The vol- ume of the bread is determined by processing the silhouette pictures in a computer, each silhouette being divided into a number of segments where the length and height of the segment are used to determine the volume of the segment in accordance with a specific formula.

This method has the drawback that certain cavities in the surface of the ready-baked bread are not visible in the silhouette picture. Since the bread often has a number of larger and smaller cavities, the method is not as accurate as desired.

Disclosure of the present invention

Technical problems

Taking into consideration the fact that the technical deliberations one skilled in the art must perform in order to offer a solution to one or more of the technical problems posed are initially an insight into the measures and/or the se- quence of measures to be taken and a choice of the means required, and on the basis thereof, the following technical problems are no doubt relevant when producing the present invention.

Taking into consideration the state of the art as described above it should be deemed a technical problem to be able to advocate a method and an arrange- ment, using simple means and with good accuracy, for measuring the volume of an object, based on the principle of placing the object in a closed, defined space, supplying a gas mixture to this space, and evaluating the increasing pressure of the gas mixture in the space in order to determine the volume of the object there- from.

A technical problem is also entailed in being able to perceive the significance of and advantages associated with placing the object in the defined space, the volume of the defined space being chosen somewhat greater than the volume of the object, wherein a first item of information representing the volume of the space when empty, and a second item of information representing a second volume of the space reduced by the presence of the object, constitute measurements enabling the volume of the object to be determined easily in a computer. A technical problem is entailed in being able to perceive the significance of and advantages associated with providing a pressure source suitable for a compressible gas or gas mixture, this pressure source being connected to said defined space serving as measurement chamber, and also to a defined space serving as reference, where both spaces are preferably equal in size.

A technical problem is then entailed in being able to perceive the significance of and advantages associated with said spaces being identical. A technical problem is also entailed in being able to perceive the significance of having each of said two spaces connected individually to a sensor for determining pressure differences, and of having the sensor connected to means utilised for evaluating the volume of the object on the basis of the information from said sensor. A technical problem is also entailed in being able to perceive the significance of having said pressure source arranged to emit pressure waves like a loudspeaker.

A technical problem is also entailed in being able to perceive the significance of and advantages associated with having the pressure source arranged to emit pressure waves of a pronounced character, such as sinus character.

A technical problem is also entailed in being able to perceive the significance of and advantages associated with having the pressure source designed to emit pressure waves having a frequency below 20 Hz, particularly within the range above 5 Hz. A technical problem is also entailed in being able to perceive the significance of said sensor being connected to each of said spaces and being sufficiently sensitive to register relatively small pressure differences occurring during a selected measuring period. A technical problem is also entailed in being able to perceive the significance of the measuring period being chosen to lie within a range below 10 seconds, between 1.0 and 5.0 seconds, for instance.

A technical problem is also entailed in being able to perceive the significance of said means being designed to convert information emitted by the sensor to digital information, thereby evaluating momentary differences between pressure variations occurring between the spaces.

A technical problem is also entailed in being able to perceive the significance of allowing said pressure variations evaluated during a measuring period to be compared with stored information relating to a number of reference volumes, etc. from earlier measurements and, upon agreement of the comparison, having a volume value generated corresponding to a designated reference volume.

A technical problem is also entailed in being able to perceive the significance of said pressure waves being selected with a maximum variation of pressure caused by an alternating voltage of 10V amplitude connected to the loud- speaker.

Considering the previous state of the art it should be deemed a technical problem to perceive the significance of and advantages associated with having two spaces, one serving as reference space and one serving as measurement chamber, communicating with each other so that the same basic pressure pre- vails in both at the start of the measuring period and also during the measuring period.

A technical problem is also entailed in being able to perceive the significance of and advantages associated with a sound source emitting sound waves to a space in the proximity of the sound source, which communicates via separate ducts, such as moulded ducts, with a reference chamber and a measurement chamber.

A technical problem is also entailed in being able to perceive the significance of and advantages associated with the volume of the measurement cham- ber being chosen depending on the size and structure of the object, thereby creating criteria for an accurate measuring result.

A technical problem is thus entailed in being able to perceive the significance of and advantages associated with selecting the number of wave motions during the relevant measuring period and performing a comparison at each wave motion.

The solution

The present invention is thus based on a method and an arrangement for measuring the volume of an object in the form of a loaf of bread, placed in a defined space, the volume of the defined space being chosen somewhat greater than the volume of the object, wherein a first item of information representing the volume of the space when empty, and a second item of information representing the volume of the space reduced by the presence of the object, constitute meas- urements enabling determination of the volume of the object.

In order to solve one or more of the technical problems listed above, the present invention proposes that a single pressure source suitable for a compressible gas or gas mixture is connected to said defined space serving as a measurement chamber, and also to a space serving as reference, said spaces preferably being identical.

It is also advocated that each of said two spaces be connected to a sensor for determining pressure differences, and that a means be utilised for evaluating the volume of the object on the basis of the information from said sensor.

Proposed embodiments falling within the scope of the inventive concept are for said pressure source to be arranged to emit sound-related pressure waves from loudspeaker equipment.

The pressure source is also arranged to emit pressure waves of a pronounced character, such as sinus character.

The pressure source is also designed to emit pressure waves having a frequency below 20 Hz.

In accordance with the invention the pressure source should be designed to emit pressure waves having a frequency above 5 Hz. In accordance with the present invention said sensor shall be connected to each of said spaces via ducts and shall be sufficiently sensitive to register small pressure differences occurring during a specified measuring period.

The invention also recommends that the measuring period shall be cho- sen to be between 1.0 and 5.0 seconds.

Said means is also designed to convert information emitted by the sensor to digital information, thereby evaluating momentary differences between pressure variations occurring between the spaces.

The invention also advocates that pressure variations evaluated during a measuring period shall be compared with stored information relating to a number of reference volumes, etc. for earlier measurements and, upon agreement of the comparison, a signal shall be generated corresponding to a volume value applicable to a designated reference volume.

The invention also recommends that said pressure waves shall be se- lected with the maximum variation of pressure obtained by voltage variation to the loudspeaker of about 10V.

Advantages

The advantages that may be primarily deemed characteristic of a method and an arrangement in accordance with the present invention are that they can be used in beneficial manner to determine the volume of a loaf of bread quickly and with extreme accuracy, even if the object is porous in character.

The method and arrangement can also be used in a production line in order to determine the volume of a bread object at various stages. This is particularly applicable in the production of bread where various properties of the bread shall be checked during the production process.

The features primarily deemed to be characteristic of a method in accordance with the present invention are defined in the characterizing part of the appended claim 1 , and the features primarily deemed to be characteristic of an ar- rangement in accordance with the present invention are defined in the characterizing part of the appended claim 14. Brief description of the drawings

A preferred embodiment of equipment suitable for operating in accordance with the method to allow measurement of the volume of a bread object placed in a defined space will now be described in more detail with reference to the accompanying drawings in which:

Figure 1 shows schematically equipment suitable for performing the proposed method, Figure 2 shows a simplified example of pressure-wave-related sinus curves which are combined in a sensor unit to a signal representing the vol- ume of an object, and

Figure 3 shows a diagram-related example of practical measurement of porous bread objects of different sizes for determining the volume of the bread object.

Description of proposed embodiment

The method advocated in accordance with the present invention, and an arrangement therefor, is used for measuring the volume of a bread object 1 placed in a space 2 defining the object 1 , where the volume 2' of the defined space 2 is chosen somewhat greater than the volume of the object 1. The ratio of the volume 1 ' of the object to the volume 2' of the measurement chamber 2 shall normally exceed 50%, e.g. towards 95%, and shall be dependent on the material structure of the object.

Fundament to the invention is that the ratio between the volume V of the object 1 and the volume 2' of the space 2 shall advantageously be chosen de- pending on the nature of the object so that a large ratio, such as 80 to 95% may be suitable in the case of an extremely resilient and porous object whereas the ratio may be chosen less, e.g. 75-90% for other, less porous objects.

For more solid objects it may be predicted that too small a difference in the volumes (space 1 /space 2) may result in excessive pressure differences and excessive differences in volumes may result in too little pressure difference for optimum conditions to give accurate measurements.

The invention is based on the availability of a first item of information representing the volume of the space 2 and/or of the space 3 when empty, e.g. the volume 3' of the space 3 when empty, and a second item of information representing the volume 2" of the space 2 reduced by the presence of the object senting the volume 2" of the space 2 reduced by the presence of the object 1 , which shall constitute measurements, detectable via measuring ducts 2a, 3a, enabling determination of the volume V of the object 1 by means of a measurement difference. Said information applies primarily to the pressure change increasing over a period of time that is applicable in the spaces 2, 3 upon simultaneously supplying a pressure surge through each of the inlet ducts.

The information may also concern the reduced pressure change occurring over a period of time in the space when a positive pressure caused by the pres- sure surges prevails in the space and this positive pressure shall be equalised via inlets to an adjacent space 5.

The use of a pressure source 4 suitable for influencing a compressible gas or gas mixture 5' is thus advocated.

The compression and decompression of the gas 5' in the space 5 via the pressure source 4 should take place with a well definable shape, such as a pronounced sinus shape or the like for the time-related pressure changes, with as little contribution from harmonics as is practically possible.

Adjustment of the shape and size of each space is necessary for this, particularly of a space 5 which is in communication with the spaces, 2, 3 via ducts 2b, 3b, in order to achieve equalisation of the basic pressure therein.

The space 5 shall also be so shaped that the pressure waves generated by the pressure source 4 can be distributed equally to both spaces 2, 3, or at least distributed predictably in both spaces.

Although the spaces 2, 3 are shown as identical in Figure 1 , it should be observed that they could also be shaped differently. However, information is required as to the differences.

During a selected measuring period, thus, the pressure source 4 is acoustically connected to said defining space or measurement chamber 2 via a duct 2b, via the space 5 and the gas mixture 5', and is also acoustically connected to a space 3 serving as reference, via a duct 3b.

Said spaces 2, 3 are preferably identical in shape and volume and, in addition, the connections and dimensioning thereof via the ducts 2b and 3b shall be identical, as well as the ducts 2a, 3a. The term "identical" shall naturally be understood to include substantially equal as regards the acoustic and pneumatic properties.

Each of said two spaces 2, 3 is connected via respective ducts 2a, 3a to a sensor 6 determining pressure differences. Said sensor shall be so sensitive that it can evaluate small variations in pressure between the spaces 2, 3 during a particular measuring period. It shall thus be able to evaluate a plurality of measured values during a measuring period in order to determine a difference curve and the mean value presentation of a number of measured values. The pressure difference transducer or sensor 6 may normally be designed for measurement within pressure differences +/- 5 cm water gauge.

There is nothing to prevent an amplifier and a low-pass filter from being connected after the sensor 6.

A means 7 provided with a computer may be used to evaluate the volume of the object from difference-related information obtained from said sensor 6.

Particularly recommended is for said pressure source 4 to be arranged to emit the required pressure waves from a loudspeaker 4a. These pressure waves shall preferably be adapted to a simple, pure curve shape, such as a pronounced sinus character or some other simple wave shape. This means that the time-related pressure change, generated by the loudspeaker 4a shall display positive and negative values corresponding to a sinus shape, superimposed on a basic pressure applicable to the spaces 2, 3 and 5.

The loudspeaker 4a is driven by circuits not shown in detail in the drawings, including amplifiers, wave-shaped generators, etc. The pressure source or loudspeaker 4 is also designed so that it can emit pressure waves having a frequency below 20 Hz during the measuring period.

A circuit required for this is not shown in detail in Figure 1.

The pressure source or loudspeaker 4 is also designed and controlled so that it can generate and emit pressure waves having a frequency above 5 Hz, be- tween 5 and 15 Hz, 10 and 18 Hz, depending on the material structure of the object.

Said sensor 6 is connected to each of said spaces 2, 3 and is sufficiently sensitive to be able to register even small pressure differences occurring during a measuring period. In the present case the measuring period shall be chosen to be between 1.0 and 5.0 seconds.

The invention also covers an embodiment in which the frequency of the pressure waves can be varied during a specific measuring period, e.g. increased and/or decreased.

The wave shape during the measuring period can thus be chosen to increase from 5 Hz to 10 Hz or to decrease from 20 Hz to 10 Hz, or vice versa.

There is nothing to prevent to prevent both an increase and a decrease in frequency, or vice versa, during one and the same measuring period. Said means 7 is designed to convert information emitted by the sensor in a unit 7a, to digital information, thereby evaluating momentary differences between pressure variations occurring between the spaces 2, 3.

The unit 7a is now connected to two memories, designated 7b and 7c.

A number of reference values may be stored in a first memory 7b. Thus values pertaining to one and the same object with different volume V may be stored. Values pertaining to one and the same object with different shape and structure may also be stored.

In accordance with the invention, thus, pressure variations evaluated during a selected measuring period may be compared with one or more combinations of one or more items of stored information in the memory 7b relating to a number of measurements performed earlier and/or reference volumes, etc.

Each measured value during a measuring period can be stored temporarily in a memory 7c.

These measured values may also be inserted as reference values in the memory 7b.

The measured values 7c occurring during a selected measuring period can be compared via a circuit 7d with measured values stored in the memory 7b where one or more lists of measured values and their equivalents in an evaluated volume for the object 1 are stored, a signal representative of a volume corre- sponding to the relevant measured values can thus be indicated and generated.

Upon agreement of the comparison a signal is generated representing a volume value equivalent to the indicated reference volume, and this is shown on a display 7e. The pressure wave is selected with a maximum pressure change adjusted to the volumes and shapes of the spaces.

Figure 1 shows an arrangement where the basic pressure is the same in spaces 2, 3 at the beginning of and throughout the measuring period. This avoids calibration which would otherwise be necessary.

Figure 2 illustrates schematically, under A, a sinus-shaped wave motion generated by the sound source 4 and in the space 5.

When this wave motion, an increase and decrease of the basic pressure in the gas 5', is allowed to pass in to the measurement chamber 2, the amplitude rises, under B, due to the volume 2" limited by the object.

When corresponding wave motion passes to the reference chamber 3 the amplitude, under C, rises less because the volume 3' has a greater value than the volume 2".

The sensor 6 can now sense the difference in pressure, under D, in the chambers 2 and 3 and can process this signal in the computer equipment 7.

Reference to Figure 3 illustrates the measurement result from a practical application with a porous object.

With such objects it is important for the basic pressure to be allowed to adjust to the prevailing atmospheric pressure and for the pressure waves gener- ated to have small amplitude values so that the object is not deformed during the negative pressure phase and/or positive pressure phase, i.e. that the measurement is not affected by a number of small gas bubbles in the object (such as a loaf of bread).

Figure 3 also illustrates three different measurements, with three objects of different sizes but having the same structure.

The object 1 is subjected to pressure changes for a period of 5 seconds, five points being measured during the measuring period. The object is relatively small in relation to the volume of the measurement chamber 2, say about 50% of its size. A somewhat larger object 1a, 1.5 times the size of the object 1 above, is measured in the same way, resulting in the curve shape in the middle of the graph. A large object 1 b, twice the size of the object 1 above, is measured in the same way and fills about 95% of the space. The resultant curve shape is shown on the right in Figure 3.

It can thus be ascertained that in the case of 50% filling ratio as in the case of the object 1 , the points measured are rather similar and with increasing filling ratio the measure values become more spread.

The invention is naturally not limited to the embodiments described above by way of example but may undergo modifications within the scope of the inventive concept illustrated in the appended claims.

Claims

1. A method for measuring the volume of an object in the form of a loaf of bread placed in a defined space, the volume of the defined space being chosen greater than the volume of the bread object, wherein information representing the volume of the space when empty, and information representing the volume of the space reduced by the presence of the object constitute measurements enabling determination of the volume of the bread object, characterized in that a single pressure source adapted for a compressible gas or gas mixture is connected, via a common space, to said defined space and also to a space serving as reference, in that each of said two spaces is connected individually to a sensor for determining pressure differences, and in that a means is utilised for evaluating the volume of the bread object on the basis of the information from said sensor.

2. A method as claimed in claim 1 , characterized in that said pressure source in the form of a loudspeaker emits said pressure waves.

3. A method as claimed in claim 2 , characterized in that the pressure source is arranged to emit pressure waves of a pronounced character, such as si- nus character.

4. A method as claimed in claim 1 or claim 2, characterized in that the pressure source is designed to emit pressure waves having a frequency below 20 Hz.

5. A method as claimed in claim 1 or claim 2, characterized in that the pressure source is designed to emit pressure waves having a frequency above 5 Hz.

6. A method as claimed in claim 1 , characterized in that said sensor is connected to each of said spaces and is sufficiently sensitive to register small pressure differences occurring during a measuring period.

7. A method as claimed in claim 6, characterized in that the measuring period is chosen to be between 1.0 and 5.0 seconds.

8. A method as claimed in claim 1 , characterized in that said means is de- signed to convert information emitted by the sensor to digital information, thereby evaluating momentary differences between pressure variations occurring between the spaces.

9. A method as claimed in claim 8, characterized in that pressure variations evaluated during a measuring period can be compared with stored information relating to a number of reference volumes, etc. for earlier measurements and, upon agreement of the comparison, a volume value is generated corresponding to a designated reference volume.

10. A method as claimed in claim 2, characterized in that said pressure waves are selected with a maximum variation of pressure equivalent to the object.

11. A method as claimed in claim 1 , characterized in that a space serving as reference and a space serving as measurement chamber communicate with each other so that the same basic pressure prevails in both.

12. A method as claimed in claim 1 , characterized in that the pressure source acts within a space that is connected in parallel with said two spaces.

13. A method as claimed in claim 1 , characterized in that the volume of the measurement chamber is chosen depending on the form and structure of the object.

14. An arrangement for measuring the bread volume of an object placed in a defined space, the volume of the defined space being chosen greater than the volume of the bread object, wherein information representing the volume of the space when empty, and information representing the volume of the space reduced by the presence of the object constitute measurements enabling determination of the volume of the bread object, characterized in that a single pressure source adapted for a compressible gas or gas mixture is connected, via individual ducts, to said defined space and also to a space serving as reference, said spaces being identical from the measuring point of view, in that each of said two spaces is connected individually via its own duct to a sensor for determining pres- sure differences, and in that a means provided with a computer is utilised for evaluating the volume of the bread object on the basis of the information from said sensor.

15. An arrangement as claimed in claim 14, characterized in that said pres- sure source is arranged to emit said pressure waves from a loudspeaker.

16. An arrangement as claimed in claim 15, characterized in that the pressure source is arranged to emit pressure waves of a pronounced character, such as sinus character.

17. An arrangement as claimed in claim 14 or claim 15, characterized in that the pressure source is designed to emit pressure waves having a frequency below 20 Hz.

18. An arrangement as claimed in claim 14 or claim 15, characterized in that the pressure source is designed to emit pressure waves having a frequency above 5 Hz.

19. An arrangement as claimed in claim 14, characterized in that said sensor is connected via ducts to each of said spaces and is sufficiently sensitive to register small pressure differences occurring during a specified measuring period.

20. An arrangement as claimed in claim 19, characterized in that one or more measuring period(s) is/are chosen to be between 1.0 and 5.0 seconds.

21. An arrangement as claimed in claim 14, characterized in that said means is designed to convert information emitted by the sensor to digital information, thereby evaluating momentary differences between pressure variations occurring between the spaces.

22. An arrangement as claimed in claim 21 , characterized in that pressure variations evaluated during a measuring period can be compared with one or more items of stored information relating to a number of reference volumes, etc. for earlier measurements and, upon agreement of the comparison, a volume value is generated corresponding to a designated reference volume.

23. An arrangement as claimed in claim 15, characterized in that said pressure waves are selected with a maximum variation of pressure depending on the object.

24. An arrangement as claimed in claim 14, characterized in that a space serving as reference and a space serving as measurement chamber communicate with each other so that the same basic pressure prevails in both.

25. An arrangement as claimed in claim 14, characterized in that the pressure source acts within a space that is connected in parallel with said two spaces.

26. An arrangement as claimed in claim 14, characterized in that the volume of the measurement chamber is chosen depending on the shape and structure of the object.