1. Precision scale having a weighing chamber (16), a weather protection (18, 20, 22) surrounding the weighing chamber (16), exactly one climate module (34) which comprises an air pressure sensor (62), an air humidity sensor (54) and an air temperature sensor (52) and which is arranged in the weighing chamber (16) in a detachable manner, a processor (32) which is arranged in the precision scale, a data input unit which is arranged on the precision scale, and a data transmission path by means of which data can be exchanged between the climate module (34) and the processor (32), wherein the processor (32) comprises a measurement uncertainty determination module (33) by means of which a measurement uncertainty of the scale can be known taking into account the data of the climate module, the climate module provides data about the microclimate within the windbreak and possible changes in the microclimate during the weighing process are also immediately applied in the determination of the measurement uncertainty, wherein the climate module can be used as a separate unit outside the scale.

2. Precision scale according to claim 1, characterized in that the climate module (34) is connected with the processor (32) by means of an electrical plug-in connection or wireless transmission.

3. Precision scale according to any of the preceding claims, characterized in that there is a sensor (58) coupled to the processor (32) for determining the degree of ionization in the weighing chamber (16).

4. Precision scale according to one of the preceding claims, characterized in that in the weighing chamber (16) there is a light sensor (56) coupled to the processor (32).

5. Precision scale according to one of the preceding claims, characterized in that the processor (32) is configured in such a way that it knows at least the air buoyancy or buoyancy correction factor of the test object from the air pressure, the air humidity and the air temperature in the weighing chamber (16) on the basis of the density of the weighing object.

6. Precision scale according to one of the preceding claims, characterized in that the measurement uncertainty determination module has a memory in which the results of previously determined measurement uncertainties are stored.

7. Method for determining the measurement uncertainty of a precision scale according to one of claims 1 to 6, having a weighing chamber (16) which is separated from the surroundings by a wind shield and in which an air pressure sensor (62), an air humidity sensor (54) and an air temperature sensor (52) are arranged, wherein the sensors (52, 54, 62) are coupled to a processor (32) and wherein weighing objects in the form of test bodies are weighed, characterized by the following steps:

-knowing the air pressure, air humidity and air temperature in the weighing chamber (16) by means of the sensors (52, 54, 62);

-weighing the subject;

-determining a standard uncertainty of the weighing method;

-determining a standard uncertainty of the mass of the subject;

-knowing the total uncertainty of the quality determination.

8. Method according to claim 7, characterized in that the reference weight (A) is weighed in addition to the subject.

9. Method according to claim 7 or 8, characterized in that the result of a previously known total uncertainty is also taken into account when the total uncertainty is known.

Background

A problem with such high-resolution electronic precision scales and mass comparators is that a large number of external parameters influence the weighing result. When the measurement error should be less than 10ppm in the case of a mass determination of the subject or in the case of a weighing process, the operator has to take into account the measurement uncertainty as well.

The measurement uncertainty is influenced in particular by the air density present at the time of measurement, which acts on the buoyancy of the test object and is dependent on the ambient temperature, the air pressure and the air humidity. The user may have an impact on the measurement result and thus on the measurement uncertainty, since the way and method how the measurement is performed has an impact on how accurately the determined measurement result can be reproduced.

DE 3714540C 2 describes a method for automatically calibrating a high-resolution scale, in which the scale performs a series of test steps, in which the scale compares disturbance variables that influence the weighing result with limit values, and performs a calibration without exceeding the limit values.

DE 29912867U 1 shows a weighing apparatus with at least one measured value sensor for climate parameters. The measured values are output on a separate display unit.

An electronic weighing scale is known from EP 0864852 a2, which calibrates one and the same load by weighing several times and statistically evaluates these data in order to increase the measurement accuracy.

When evaluating the measurement uncertainty of a metrology process, all influencing factors are taken into account. For this purpose, it is described, for example, in the international code of OIML R111 how the uncertainty is to be evaluated. For this reason, PC programs and Excel-based solutions for performing uncertainty calculations are well known in the art. The data of the scale, the climate and the reference weight are input into a formula which is processed there. In addition to the PC that performs the calculations, external sensors are also required, which are used to receive the climate data. The software on the PC calculates the total uncertainty for the weighing process from the weighing values of the scale, from the climate sensor values, the parameters of the input reference weights and other uncertainty parameters.

A disadvantage of this solution is that data from a plurality of systems (scales, climate sensors for determining the air density, reference weights, etc.) must be transmitted into the PC. In principle, there is a risk of incorrect input here. A PC is also always required for the evaluation, which PC performs the calculation of the uncertainty and which PC uses a database with information, for example of the reference weights used. The computer has no influence on the total weighing process; it can only read the weighing value from the scale. Thus, a scale may be viewed as a simplified sensor that provides a weighed value.

Disclosure of Invention

The object of the present invention is to provide a precision scale or mass comparator and a method with which the determination of the measurement uncertainty is simplified and which makes it possible to output the measurement uncertainty directly together with the weighing result.

In order to solve this object, according to the invention a precision scale is provided, which has a weighing chamber, a weather module which surrounds the weighing chamber and is arranged in the weighing chamber in a detachable manner and which contains an air pressure sensor, an air humidity sensor and an air temperature sensor, a processor arranged in the precision scale, a data input unit arranged on the precision scale, and a data transmission path, with which data can be exchanged between the weather module and the processor, wherein the processor contains a measurement uncertainty determination module with which an uncertainty of the scale can be determined. In order to solve this object, a method is also provided for determining the measurement uncertainty of a precision scale or mass comparator having a weighing chamber which is separated from the surroundings by a wind shield and in which an air pressure sensor, an air humidity sensor and an air temperature sensor are arranged, wherein these sensors are coupled to a processor and wherein a weighing object in the form of a test body is weighed. According to the invention, during the weighing process, the air pressure, the air humidity and the air temperature in the weighing compartment are known by means of sensors. In addition, the subject is weighed. The following uncertainty is then determined, for example, from OIML R111-1: standard uncertainty of the weighing method, uncertainty due to the standard used, uncertainty of the scale, and uncertainty of the air buoyancy correction. Finally, the total uncertainty determined for the quality is known. The basic idea behind the invention is to integrate all components necessary for determining the measurement uncertainty into a scale. The climate module provides data about the microclimate present around the subject, i.e. within the windbreak. Possible changes in the microclimate during weighing also apply immediately to the determination of the measurement uncertainty. It is not necessary that the acquired climate data and their uncertainties are entered manually; thereby preventing erroneous input. Since all the components necessary for determining the measurement uncertainty are integrated into the weighing apparatus itself, the latter can be transported by the operator to the location where the weighing process is to be carried out, depending on the type of self-sufficient weighing laboratory.

In general, it can be provided that the user performs the weighing process reliably, for example, with a mass calibration according to OIML R111-1, and in this case the actual mass and all the associated uncertainties are also calculated in addition to the conventional mass. At the end of the mass calibration, the weighing machine issues an evaluation of the test weights according to a predefined level of accuracy and provides all the data for issuing a test certificate of eligibility. The scale works like a mass laboratory, since all necessary sensors and data for making a mass determination are integrated into the scale.

The weighing apparatus preferably comprises a user interface (display) in order to carry out the mass calibration according to a predefined process program, for example in a user-guided manner. The load change necessary for mass determination is known from the reference weight and the test weight, and mass calibration is discontinued in the event of a faulty operation. The scale performs a plausibility test and evaluation based on a standard deviation of the mass difference between the reference weight and the subject, and compares the standard deviation with a previous standard deviation. The permissible uncertainty of the level of accuracy to be calibrated for the weight is checked and evaluated. The scale may also automatically open the door of the weatherproof portion to enable load replacement. All necessary sensors for mass determination are integrated in the scale and the uncertainties of all sensors are stored in the scale in order to calculate a total uncertainty for the mass determination.

Standard uncertainty u of weighing method (class A)_wIn terms of the mean standard deviation s of the scales (on different days)_pTo know, or alternatively to calculate from the standard deviation of the mass difference between the reference weight and the subject. Uncertainty u (m) of reference weight (class B)_cr) And instability U of the reference weight_inst(m_cr) Is stored in the scale and is used to calculate the total uncertainty. Air buoyancy corrected (class B) uncertainty u_bFrom the uncertainty calculations of the climate sensors for temperature, air pressure and relative air humidity integrated in the scale and from the uncertainty of the densities of the reference and test object weights and the uncertainty component of the formula for calculating the air buoyancy correction. Uncertainty component u of a scale_baCalculated from the uncertainty due to the display resolution of the digital scale, the uncertainty due to an out-of-center load, the uncertainty due to magnetic effects on the sample (or weight), and an uncertainty factor based on the sensitivity of the scale.

In order to solve the above-mentioned object, a climate module is also provided for the releasable electrical coupling to the precision scale or the mass comparator, wherein the climate module forms a closed structural unit and has an air pressure sensor, an air humidity sensor and an air temperature sensor as well as a part of a data transmission path via which data can be transmitted to a processor outside the climate module. Since the climate module is replaceable (i.e. can be released from the scale in a non-destructive manner), it can be sent to an external research institute or service provider for calibration, if necessary. During this time, the precision scale or the mass comparator can continue to operate by using an alternative climate module. In this way, it is possible to take one or (in the case of a plurality of precision weighers) a plurality of climate modules in rotation at all times during the calibration, while the remaining climate modules are used for the measurement. Overall, the user is provided with a compact weighing laboratory which can even be transportable and which integrates all the components and functions necessary for the air buoyancy correction of the weighing values into a precision scale or mass comparator. Therefore, an external computer, sensor, or the like is not required. An additional advantage is obtained in the determination of the measurement uncertainty, namely that old scales can be retrofitted. For this purpose, only the software of the processor needs to be supplemented in addition to the data transmission path.

An advantage of the precision scale according to the invention is that, in terms of accuracy, the climate data is measured in the windbreak (and not only in the room in which the scale is located). Thus, the air density is known in the immediate vicinity of the subject. Furthermore, since the buoyancy value and its uncertainty are automatically forwarded to the processor, possible transmission errors, such as the transmission of the value from a so-called calibration certificate into the calibration software, are virtually precluded.

According to one embodiment, it is provided that the climate module is connected to the processor by means of an electrical plug-in connection or by means of a wireless transmission. The plug-in connection can be integrated into a mechanical receptacle for mounting the climate module in the precision scale. In this way, when the climate module is arranged in its position in the wind shield, a data transmission path to the processor is then automatically established. In the case of wireless transmission, the climate module can be arranged in any position inside the windbreak, for example on the side wall which minimizes the disturbance of the climate module, irrespective of whether the plug-in part can be suitably arranged in this position. Furthermore, the elimination of the plug is advantageous in that the interior of the weighing chamber can be made smoother and can thus be implemented in a better cleanable manner.

It can additionally be provided that a sensor for determining the degree of ionization is present in the weighing chamber, which sensor is coupled to the processor. Thereby, additional parameters can be determined and can be taken into account when correcting the symmetry values. Depending on the determined degree of ionization, an output signal is generated by the processor, for example in order to actively change the degree of ionization by using an ionization device which is activated from the point at which the particular degree of ionization is reached. In addition, the display may also indicate to the user as follows: the degree of ionization inside the weighing chamber is too high and de-charging should be carried out.

It may also be provided that a light sensor is present in the weighing compartment, which light sensor is coupled to the processor. Thereby, further parameters can be determined again and can be taken into account when correcting the symmetry values. The processor may send the output signal from a predetermined incidence of light. The influence of the light incidence on the weighing process can thus be determined in order to take measures in the process itself, if necessary. The output signal may also be displayed.

According to one embodiment, it is provided that the processor is designed in such a way that it knows at least the air buoyancy or the buoyancy correction factor of the object on the basis of the density of the weighing objects from the air pressure, the air humidity and the air temperature in the weighing compartment. In this way, the climatic values which are mathematically traceable can be obtained from the climatic modules in a time-synchronized manner for the acceptance of the weighing values, with which the processor can correct the weighing values and learn and display the quality or the regular quality.

According to one embodiment, an electronic memory, in particular an EEPROM, is provided, which can be read from the outside and can store calibration values and correction values for the climate module. For the adjustment, the calibration values and correction values can be stored in an electronic memory on the climate module, in particular an EEPROM. This can also be done without a scale. When the climate module is then coupled to the precision scale again, this data is supplied directly to the processor of the scale. In addition, at least some of the following information for performing the sensor calibration may be stored in the memory, in particular: the number of the calibration certificate, the current calibration value, the date of calibration, the names of the calibration lab and the processing personnel, and the history of the calibration. In the memory of the climate module, so-called uncertainty values for each climate variable can also be stored, so that, for example, compared to the calculation of the air density, the uncertainty of the air density is likewise calculated by means of a precision scale.

According to one embodiment, the climate module can also be used outside the weighing scale as a separate unit and can be connected to the weighing scale via a connectionI²The C bus is coupled to a USB port of the PC. This facilitates external calibration. Furthermore, the climate module may be used in other applications to receive the climate parameter without coupling it to a scale. The circuit board of the climate module can have plug projections for this purpose with little effort, so that it can be connected to the USB adapter.

In order to solve the above-mentioned object, a method for determining the measurement uncertainty of a precision scale having a weighing chamber which is separated from the surroundings by a wind shield and in which an air pressure sensor, an air humidity sensor and an air temperature sensor are arranged, wherein these sensors are coupled to a processor, and wherein the weighing object is weighed in the form of a test object, is furthermore provided. Here, the air pressure, air humidity, and air temperature in the weighing chamber are known by means of sensors, and the subject is weighed. Furthermore, the standard uncertainty of the weighing method and the uncertainty of the mass of the subject are also determined. From which the total uncertainty of the weighing result is known. The advantages obtained are evident on the basis of the above explanations.

Furthermore, it can be provided that the result of the previously known total uncertainty is also taken into account when the total uncertainty is known. The plausibility of the current overall uncertainty known can be assessed on the one hand on the basis of the overall uncertainty known from the previous measurement. When the previously known total uncertainty is significantly less than the currently known total uncertainty, then an indication may be provided to the user that the weighing process is generally unsatisfactory. On the other hand, when the currently known total uncertainty is significantly lower than the total uncertainty of the previous weighing process, then the currently known total uncertainty can be corrected slightly upwards.

Drawings

Additional features and advantages of the invention will be derived from the following description and from the following drawings with reference to the accompanying drawings. Wherein:

figure 1 shows an exploded view of a precision scale according to the present invention;

figure 2 shows a perspective view of a climate module according to the invention, which can be used in a precision scale according to the invention;

fig. 3 shows a side view of the climate module according to fig. 2 without an outer housing;

fig. 4 shows a top view of the climate module of fig. 2 also without an outer housing;

fig. 5 shows a flow chart reflecting a method for operating a scale; and is

FIG. 6 shows a flow chart reflecting a method for determining the total uncertainty of the mass comparison according to OIML R111-1 performed with a scale.

Detailed Description

In fig. 1, a high resolution electronic precision scale is shown, which in this embodiment is capable of achieving mass contrast in all precision levels according to OIML R111-1 and according to ASTM E617-13.

The precision scale comprises a weighing cell 14 with a base 12, into which a weighing system 10, not shown in detail, is fitted. The weighing cell 14 also comprises a weighing chamber 16, which is formed by a wind-proof part having adjustable side walls 18, a front wall 20 and a rear wall 22. The weighing chamber 16 can be separated from the surroundings by a wind shield. The weighing pan 24 serves to cradle the weighing object.

An electronic evaluation system 26, which is embodied here as a separate part, is electrically coupled to the weighing cell 14 via a cable 28. The display unit 30 coupled to the evaluation system 26 serves both as a display and as a data input unit.

In particular, a processor 32 is installed in the electronic evaluation system 26, which receives data from the weighing cells 14.

Furthermore, a measurement uncertainty determination module 33 is provided in the electronic evaluation system 26, with which the measurement uncertainty of the current weighing process can be determined. Furthermore, a memory is integrated into the measurement uncertainty determination module 33, in which the total uncertainty of the previous weighing process is stored.

In the weighing compartment 16, a climate module 34 is provided, which is designed as a structurally separate unit and which can be mechanically coupled to the rear wall 22 (i.e. can be mounted in a non-destructive manner) via a releasable plug-in connection, preferably without the aid of tools.

For this purpose, the rear wall 22 has two slots 36 spaced apart from one another, into which flexible latching hooks 38 (see also fig. 2) on an outer housing 40 of the climate module lock.

The climate module 34 is shown in detail in fig. 2 to 4.

The outer housing 40 has a number of openings 42, via which the interior of the outer housing 40 enters the weighing compartment 16 and becomes part of the weighing compartment 16, so that the climate inside the weighing compartment 16 corresponds to the climate in the interior of the outer housing 40.

The climate module 34 is coupled electronically via electrical plugs with corresponding plug receptacles 44 in the rear wall 22, the plug receptacles 44 being in electrical connection with the processor 32. The plug 46 is inserted into the plug receptacle 44 with a contact 48 on the climate module 34. The plug 46 thus forms part of the module side of the electrical plug-in connection.

As an alternative to the electrical plug-in, wireless transmission, for example WLAN or bluetooth, may be used.

The electrical plug-in (or alternatively used wireless transmission) forms a data transmission path with which data can be transmitted from the climate module 34 to the processor 32 and back if necessary.

The plug 46 is preferably a section of a circuit board 50, on which a plurality of sensors for detecting the climate in the weighing chamber 16 are arranged. On the circuit board 50, therefore, an air temperature sensor 52, an air humidity sensor 54, a light sensor 56 arranged directly in the vicinity of the opening 42 and a sensor 58 for detecting the degree of ionization in the weighing chamber 16 are provided, as well as an electronic memory 60. The air pressure sensor 62 is mechanically and electrically coupled with the circuit board 50 via a bracket 64.

It is also possible to group a plurality of sensors into a combined sensor.

The wall 66 closes the shell-like outer housing 40, so that a narrow, tongue-like section of the circuit board 50, which section is located to the right of the wall 66 in fig. 4, can be inserted into the rear wall 22 and the plug receptacle 44.

Each sensor 48 is coupled with the processor 32 via a respective contact 48. Likewise, the memory 60 is coupled to the processor 32.

When the scale is operated as a comparator-type scale, the scale operates according to the following method, which is explained in connection with fig. 5:

in steps 100 and 102, the density of the weighing objects (the object under test, also referred to as object B, and the reference weight a) is input into the comparator-type weighing machine, for example, via the display unit 30, which at the same time is used as a data input unit, for example, also via a touch screen. Alternatively, the density of the weighing object may already be stored.

The weighing objects are placed on the weighing pan 24, to be precise according to predefined process steps, for example, first the reference weight a is placed, then the test object B is placed twice and finally the reference weight a is placed again. This involves a comparison weighing (double substitution), from which the display difference of the scale is obtained in step 104. Other flow steps are possible, such as ABA instead of ABBA.

The air pressure, air humidity and air temperature are known by the sensors 62, 54 or 52 in step 106, which then forward the corresponding data to the processor 32.

The air density is determined in the processor 32, see step 108. In step 110, the input density is used in the processor to determine the air buoyancy correction factor and/or the air buoyancy of the weighing object in relation to the air pressure, the air humidity, the air temperature and the density of the weighing object, and in step 112 the conventional weighing value of the object B is determined, i.e. the mass of the object B corrected for its air buoyancy is determined and reflected as a record in the display unit 30, wherein the conventional mass 114 of the reference weight is used in the determination of the conventional mass of the object.

Furthermore, calibration values and correction values for the climate module 34 are stored in the memory 60, which are stored when the climate module 34 is calibrated.

The calibration is performed outside the comparator-type scale. For this purpose, the climate module 34 is simply pulled out of the weighing compartment 16 without the wiring having to be loosened. The climate modules 34 are then sent to the respective calibration institute, which stores the number of the calibration certificate, that is to say the new calibration value, the calibration date, the name of the calibration laboratory and the processing staff and the calibration history in the memory 60. Thereafter, when climate module 34 is again placed in a precision scale or comparator scale, these values are read by the application and applied directly to the calculation.

The value of the light sensor 56 and the value of the sensor 58 for determining the degree of ionization in the weighing chamber 16 are also determined.

For example, in the case of increased light incidence, a corresponding signal is provided on the display, for example, an inaccurate measurement is caused by an increase in solar radiation and thus a change in the temperature in the weighing compartment. Thus, the output signal is given by the processor in relation to the light incidence.

As soon as the degree of ionization is too high, an ionization device is activated, which ionizes the air in the weighing chamber and assumes the charge removal of the weighing object, or which warns before the weighing object has too high a charge.

The memory 60 is preferably an EEPROM.

Furthermore, the connection between climate module 34 and the rest of the precision scale or comparator scale is via I²C bus.

The climate module 34 can also be coupled to a computer via a USB adapter into which the climate module is plugged in order to calibrate the sensors 52 to 58 and 62 without the need to couple the climate module 34 to the weighing system 10.

The total uncertainty of the mass determination is determined in the following manner (see also fig. 6):

the standard deviation s is first determined from the results of the calibration cycle. The standard deviation is compared with the average standard deviation s of the previous measurements_pA comparison is made. The standard deviation learned in these measurements is stored in the memory of the measurement uncertainty determination module 33. If it is currentThe current weighing process is aborted if the difference between the standard deviation and the mean standard deviation of the previous measurements is greater than a reasonably defined value. Otherwise, the class a uncertainty of the weighing process is determined from this standard deviation.

Air buoyancy corrected class B uncertainty u_bFrom the air density, the material density of the reference and the uncertainty of the material density of the subject. The value of the uncertainty for the air density is stored in the climate module 34; these values are stored there when they are calibrated.

Class B uncertainty u of scale_baBased on the uncertainty u due to the sensitivity of the scale_EUncertainty u due to display resolution of scale_dUncertainty u of the scale due to eccentric loading_EAnd scale uncertainty u due to magnetism_maTo calculate.

The extended total uncertainty of the weighing process is calculated from the value of the class B uncertainty corrected for the air buoyancy and from the class B uncertainty of the scale, from the class a uncertainty for the weighing process and additionally from the known uncertainty of the mass of the reference. A particular advantage is that this can be carried out in an integrated manner in the scale by means of the measurement uncertainty determination module 33, to which only information about the subject used and the reference used needs to be input. All other data are either stored there or accessed automatically, for example by calling up the uncertainty values stored in the climate modules. This enables an automated provision of the corresponding total uncertainty in the weighing process.

List of reference numerals

10 weighing system

12 base

14 weighing cell

16 weighing chamber

18 side wall

20 front wall

22 rear wall

24 weighing pan

26 evaluation system

28 Cable

30 display unit

32 processor

33 measurement uncertainty determination module

34 climate module

36 gap

38 latch hook

40 outer case

42 opening

44 plug receiving part

46 plug

48 contact part

50 circuit board

52 air temperature sensor

54 air humidity sensor

56 light sensor

58 sensor

60 memory

62 air pressure sensor

64 support

66 wall

100 step(s)

102 step

104 step

106 step

108 step

110 step

112 step

114 reference to the conventional mass of the weight

Reference weight A

B, the subject.