METHOD OF OPERATING A BALANCE WITH IONIZER

Abstract

A method for operating a balance includes: (a) introducing an ion cloud into a weighing chamber to bring an electrostatic charge state of a weighing sample towards an electrostatic neutral state, (b) detecting the neutral state, and (c) acquiring measured values of a weighing sensor, calculating therefrom a final weighing value representing the electrostatic neutral state, and outputting the final weighing value. When the ionizer is activated, the measured values of the weighing sensor are acquired, preliminary weighing values are calculated from the measured values and the final weighing value is calculated and output after a number of preliminary weighing values have been recognized as stable. During a recognition phase, positive and negative ion clouds are alternatingly generated, and during a neutralization phase, only ion clouds of that sign are generated that, in the recognition phase, had led to the larger changes within the preliminary weighing values.

Claims

1. A method for operating a balance with a weighing sample receptacle arranged in a weighing chamber for receiving a weighing sample, a weighing sensor mechanically connected to the weighing sample receptacle, an ionizer configured to introduce positive and negative ion clouds into the weighing chamber, and weighing electronics controllingly connected to the weighing sensor and to the ionizer, comprising: with the ionizer the ion clouds into the weighing chamber, to bring an actual electrostatic charge state of the weighing sample toward to an electrostatic neutral state of the weighing sample, detecting the electrostatic neutral state, within specified electrostatic tolerances, achieved by the ion clouds, acquiring measured values of the weighing sensor, calculating from the measured values a final weighing value representative of the electrostatic neutral state, and outputting the final weighing value, wherein, once the ionizer introduces the ion clouds into the weighing chamber, the measured values of the weighing sensor are acquired on an ongoing basis, preliminary weighing values are calculated from the acquired measured values on an ongoing basis, and the final weighing value is calculated and output after a predetermined number of consecutively calculated ones of the preliminary weighing values have been recognized as stable within predetermined weighing-value tolerances, wherein during a recognition phase, the positive and the negative ion clouds are alternatingly introduced with the ionizer, and during a neutralization phase following the recognition phase, only ion clouds that are only positive or are only negative are introduced with the ionizer in accordance with a determination, in the recognition phase, of whether the positive ion clouds or the negative ion clouds led to larger changes within the consecutively calculated, preliminary weighing values.

2. The method according to claim 1, further comprising: after recognizing the preliminary weighing values as being stable and before calculating the final weighing value, deactivating the ionizer and, subsequently, detecting further measured values of the weighing sensor, calculating further preliminary weighing values on an ongoing basis until a predetermined number of consecutively calculated further preliminary weighing values have been recognized as stable within predetermined tolerances.

3. The method according to claim 2, wherein the final weighing value is calculated exclusively from the further preliminary weighing values.

4. The method according to claim 1, wherein the weighing chamber is bounded on all sides thereof by a draft shield configured to open and close the weighing chamber.

5. The method according to claim 4, wherein opening the draft shield to unload the weighing sample receptacle activates the ionizer.

6. The method according to claim 1, wherein loading the weighing sample receptacle activates the ionizer.

7. The method according to claim 1, wherein detecting a signal of a proximity sensor triggered by crossing a charging path activates the ionizer.

8. The method according to claim 1, wherein actuating a switch activates the ionizer.

9. The method according to claim 1, wherein said activating the ionizer comprises switching the ionizer on and off in a pulsed manner and said acquiring measured values comprises determining correction terms for mathematical correction of the final weighing value from changes in consecutively calculated preliminary weighing values occurring when the ionizer is switched off.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1: a schematic representation of a balance for carrying out the method according to the invention,

[0037] FIG. 2: a first exemplary curve of weighing values during operation of a balance with ionizer according to the invention as shown in FIG. 1,

[0038] FIG. 3A: a second exemplary curve of weighing values during operation of a balance according to the invention with the ionizer switched on and off in a pulsed mode,

[0039] FIG. 3B: a third exemplary curve of weighing values during operation of a balance according to the invention with the ionizer switched on and off in pulsed mode, and

[0040] FIG. 4: a fourth exemplary curve of weighing values during operation of a balance according to the invention, comprising a detection phase and a neutralization phase.

DESCRIPTION

[0041] In order to be able to carry out the method for operating a balance according to the invention, a balance is required which has certain features. An example of such a balance suitable for carrying out the method according to the invention is shown in FIG. 1. The balance 10 of FIG. 1 comprises a weighing chamber 12—which is not absolutely necessary for the invention, but is advantageous—which is bounded on all sides by a draft shield 24. In the weighing chamber 12 there is a weighing sample receptacle 14 on which a weighing sample to be weighed can be positioned. In order for the weighing sample to be able to be introduced into the weighing chamber 12 bounded by the draft shield 24 and to be deposited on the weighing sample receptacle 14, the draft shield 24 has at least one openable wall element, for example an openable side wall. The weighing receptacle 14 arranged in the weighing chamber 12 is mechanically connected to a weighing sensor 16, which in turn is connected to an electronic weighing system 20. Using the weighing sensor 16, measured values are recorded, with which the weighing electronics 20 calculate weighing values, which correspond to the mass of the sample to be weighed. The balance 10 further comprises a display 22, on which weighing values can be output and displayed. In addition, the balance 10 comprises an ionizer 18 configured to introduce an ion cloud into the weighing chamber 12.

[0042] FIG. 2 shows a first exemplary curve of weighing values 28 during operation of a balance 10 with an ionizer 18 as shown in FIG. 1. In FIG. 2, a stable zero value can initially be seen at the time t.sub.1, with unloaded weighing sample receptacle 14. At the moment t.sub.2, when the weighing sample is placed on the weighing sample receptacle 14, there is a clear jump in load. When the weighing sample is placed on the weighing sample receptacle 14, the weighing sensor 16 begins to produce measured values from which preliminary weighing values are calculated on an ongoing basis by the weighing electronics 20. The measured values of the weighing sensor 16 are preferably recorded when it is registered that the weighing sample receptacle 14 is loaded and the draft shield 24 is closed. However, the recording of the measured values can also be started solely by the loading of the weighing sample receptacle 14 or the closing of the draft shield 24.

[0043] At time t.sub.3 the ionizer 18 is activated. In the present example, the ionizer 18 is switched on permanently in its activated state (time period T.sub.1), with both positive and negative ions being generated simultaneously. In a situation with electrostatically charged weighing sample 18 activation of the ionizer is noticeable by a time-dependent change in the weighing values, or more precisely, the preliminary weighing values decrease with time. This is due to the fact that an ion cloud is generated by the ionizer 18, which is introduced into the weighing chamber 12, where the charges of the ion cloud recombine with those of the weighing sample to be weighed. The recombination, in turn, causes a change in the prevailing Coulomb forces and thus a change in the vertical force component that acts on the weighing sample receptacle 14 in addition to the weight force acting on the weighing sample, which is also detected by the weighing sensor 16. FIG. 2 shows how a possible weighing value curve 28 looks if the loading of the weighing sample receptacle 14 (time t.sub.2) and the activation of the ionizer 18 (time t.sub.3) occur at different times, or more precisely, if the activation of the ionizer 18 occurs only after the loading of the weighing sample receptacle 14. This selected example serves only to illustrate the effect of ionizer activation on the weighing value curve 28. Preferably, the ionizer 18 is already activated by the opening of the draft shield 24 when the weighing sample receptacle 14 is still unloaded or by the signal of a proximity sensor that crosses a charging path—i.e., before the weighing product receptacle 14 is loaded. Similarly, the ionizer 18 can be activated by loading the weighing sample receptacle 14 (i.e., simultaneously with loading the weighing sample receptacle 14) or by actuating a switch.

[0044] When the ionizer 18 is activated (time period T.sub.1), the electrostatic charge state of the electrostatically charged weighing sample thus approaches its electrostatic neutral state, which is indicated by changes in the preliminary weighing values. Accordingly, when the electrostatic neutral state of the weighing sample is reached within predetermined tolerances, this is recognized by the fact that a predetermined number of consecutive, preliminary weighing values remain stable, as is the case in FIG. 2 at time t.sub.4.

[0045] In FIG. 2, a smaller load jump can also be seen at time is after the stability of the preliminary weighing values has been established. This results from deactivation of the ionizer 18, because even if the electrostatic charge of the weighing sample is already in its neutral state and the charges of the ion cloud generated by the ionizer 18 no longer interact with the charges of the weighing sample, the ion wind generated by the ionizer 18 still has an undesirable, distorting effect on the calculated weighing values.

[0046] In order not to include this effect on the weighing value calculation, after deactivation of the ionizer 18 at time t.sub.5, as shown in FIG. 2, further preliminary weighing values are preferably calculated on an ongoing basis until, as at time t.sub.6, a predetermined number of these consecutively calculated further preliminary weighing values remains stable within predetermined limits. Only then is the final weighing value calculated and output—ideally exclusively from the further preliminary weighing values.

[0047] FIG. 3A shows a second exemplary course of weighing values 28′ during operation of the balance 10 with ionizer 18. Reference signs which correspond to those in FIG. 2 correspond to the points in time or time periods there. In contrast to FIG. 2, FIG. 3A shows a weighing value curve 28′ in which the ionizer 18 is switched on and off in a pulsed manner in its activated state (time period T.sub.1). In FIG. 3A, the times at which the ionizer is switched on are indicated by tai and those at which the ionizer is switched off by t.sub.32. If—as shown in FIG. 3A—the electrostatic charge state of the weighing sample is the only interfering factor present in the weighing chamber 12 that affects the accuracy of the weighing value, the consecutively calculated, preliminary weighing values change only when the ionizer 18 is switched on, but not when it is switched off.

[0048] If, on the other hand—as shown in the weighing sample weighing value curve 28″ in FIG. 3B—at least one other interference factor is present in the weighing chamber 12 in addition to the electrostatic charge of the weighing sample, which impairs the precise determination of the mass of the weighing sample (e.g., temperature fluctuations), changes in consecutively calculated, preliminary weighing values can be detected even with the ionizer 18 switched off. In order to minimize the influence of these additional disturbing factors on the final weighing value, the method described here determines correction terms from the changes in the weighing value when the ionizer 18 is switched off, which can be used to mathematically correct the final weighing value.

[0049] Finally, FIG. 4 shows a fourth exemplary sequence of weighing values 28′″ during operation of a balance 10 with ionizer 18. Here, the ionizer operation is divided into a detection phase (time period T.sub.2) and a neutralization phase (time period T.sub.3). In the detection phase T.sub.2, initially only positive or only negative ion clouds are alternatingly generated by the ionizer 18 and introduced into the weighing chamber 12. The times at which only positive ions are generated are marked t.sub.33; the times at which only negative ions are generated are marked t.sub.34. In the example shown, the weighing sample is predominantly negatively electrostatically charged, so introducing positively charged ion clouds into weighing chamber 12 causes greater changes in the preliminary weighing values than introducing negatively charged ion clouds. The electrostatic charge state of the weighing sample is detected by the weighing electronics 20 based on this difference in the weight reading 28′″. Accordingly, in the neutralization phase T.sub.3, which follows the detection phase T.sub.2, only an ion cloud of that sign is generated by the ionizer 18 which is opposite to the electrostatic charge state of the weighing sample. In this way, the neutralization of the electrostatic charge of the weighing sample can be further accelerated, thereby beneficially reducing the total duration of the weighing process.

[0050] The embodiments discussed in the specific description and shown in the figures are only illustrative examples of embodiments of the present invention. The person skilled in the art is provided with a wide range of possible variations in light of the present disclosure. The applicant seeks, therefore, to cover all such variations as fall within the spirit and scope of the invention, as defined by the appended claims, and equivalents thereof.

LIST OF REFERENCE SIGNS

[0051] 10 balance [0052] 12 weighing chamber [0053] 14 weighing sample receptacle [0054] 16 weighing sensor [0055] 18 ionizer [0056] 20 weighing electronics [0057] 22 display [0058] 24 draft shield [0059] 28, 28′, 28″, 28′″ weighing value curve [0060] t.sub.1 zero value with unloaded weighing sample receptacle [0061] t.sub.2 weighing value when the load receptacle is loaded [0062] t.sub.3 weighing value curve when activating the ionizer [0063] t.sub.31 weighing value curve with ionizer switched on [0064] t.sub.32 weighing value curve with ionizer switched off [0065] t.sub.33 weighing value curve when positively charged ion clouds are introduced into the weighing chamber [0066] t.sub.34 weighing value curve when negatively charged ion clouds are introduced into the weighing chamber. [0067] t.sub.4 weighing value curve when the weighing sample reaches the electrostatic neutral state [0068] t.sub.5 weighing value curve when deactivating the ionizer [0069] t.sub.6 weighing value curve after deactivating the ionizer [0070] T.sub.1 weighing value curve when the ionizer is activated [0071] T.sub.2 detection phase [0072] T.sub.3 neutralization phase