Method for operating a scale with ionizer

Abstract

Method for operating a scale (10) with a weighing fixture (14) arranged in a weighing chamber (12) for receiving weighing material, a weighing sensor (16) mechanically connected to the weighing fixture (14), an ionizer (18) by means of which an ion cloud can be introduced into the weighing chamber (12), and weighing electronics (20) connected to the weighing sensor (16) and the ionizer (18) by means of control technology, comprising the steps: - Introducing an ion cloud into the weighing chamber (12) to approximate the electrostatic charge state of the material being weighed, if present, to its electrostatic neutral state by means of the ionizer (18), - Detecting the electrostatic neutral state achieved within specified tolerances and - Acquisition of measured values ​​from the weighing sensor (16), calculation of a final weighing value representative of the electrostatic neutral state and output of the final weighing value, wherein, with the ionizer (18) activated, measured values ​​from the weighing sensor (16) are continuously recorded, from which preliminary weighing values ​​are continuously calculated, and wherein, after a predetermined number of successively calculated preliminary weighing values ​​have been recognized as stable within specified tolerances, the final weighing value is calculated and output, characterized by that during a detection phase using the ionizer (18) alternatingly positive and negative ion clouds are generated, and during a neutralization phase following the detection phase only an ion cloud of the sign that led to larger changes in the successively calculated preliminary weight values ​​during the detection phase.

Description

Field of the invention

[0001] The invention relates to a method for operating a balance with a weighing sample holder arranged in a weighing chamber for receiving weighing samples, a weighing sensor mechanically connected to the weighing sample holder, an ionizer by means of which an ion cloud can be introduced into the weighing chamber, and weighing electronics connected to the weighing sensor and the ionizer for control purposes, comprising the steps: - Introducing an ion cloud into the weighing chamber to bring the electrostatic charge state of the weighing sample - if present - closer to its electrostatic neutral state by means of the ionizer, - Detection of the electrostatic neutral state achieved within specified tolerances and - Recording measured values ​​from the weighing sensor, calculating a final weighing value representative of the electrostatic neutral state, and outputting the final weighing value. With the ionizer activated, measured values ​​from the weighing sensor are continuously recorded, from which preliminary weighing values ​​are continuously calculated. and wherein, after a predetermined number of consecutively calculated preliminary weighing values ​​have been recognized as stable within predetermined tolerances, the final weighing value is calculated and output. State of the art

[0002] Such a method is known from JP 2016-173 308 A.

[0003] Commercially available analytical or precision balances have a weighing sample holder for weighing samples, which is located within a weighing chamber. The weighing chamber is usually enclosed on all sides by a draft shield, which has at least one openable wall element to allow the sample to be positioned on the weighing sample holder. A weighing sensor is mechanically connected to the weighing sample holder. This sensor can be used to record measured values. Based on these values, a weighing value corresponding to the mass of the sample is calculated using weighing electronics connected to the weighing sensor. The weighing value is then output, usually by showing it on a scale display.

[0004] In order to determine the mass of a sample as precisely as possible and output a reliable weight value, all factors that could adversely affect the accuracy of the weighing value must be minimized during the weighing process. One of these interference factors is the presence of electrostatic charges in the weighing chamber and sometimes directly on the sample itself.

[0005] Electrostatic charging of the sample becomes particularly problematic when—as is usually the case—the sample is weighed in a container made of non-conductive, i.e., electrically insulating, material; this prevents the charge from dissipating. The sample holder itself, however, is usually made of metal and therefore does not become electrostatically charged. Instead, charges can usually dissipate via a conductive connection to the scale housing.

[0006] If an electrostatically charged sample is placed in a container made of non-conductive material on the scale's weight support, a potential difference develops between the sample and the grounded scale components. Due to the Coulomb force, the differently charged particles attract each other, while particles of the same charge repel each other. The vertical component of this force is added to the weight force acting in the vertical direction. It is therefore also detected by the weighing sensor and the weighing electronics and subsequently distorts the calculated weight value, which has a negative impact, particularly on weighing processes with high-resolution scales.

[0007] To minimize the influence of electrostatic charges on the weighing value, it is common practice to equip balances with ionizers. Such ionizers are capable of ionizing air molecules using high-voltage electrodes. The sign of the ions generated at an electrode tip corresponds to the sign of the voltage applied to the respective high-voltage electrode. Ionizers typically comprise at least two high-voltage electrodes and are operated in such a way that both positive and negative ions are generated. The generated ions form an ion cloud that spreads throughout the weighing chamber. When they collide, the charges of the ion cloud can interact with the charges of an electrostatically charged sample and neutralize them.

[0008] Such a scale with an ionizer is known from EP 1 813 920 B1. There, the ionizer is activated based on data from an electrostatic sensor based on the principle of detecting electrostatic charges or the field mill principle, which can detect the magnitude and / or sign of electrostatic charges on the weighing sample. During a weighing process, a sample is placed on the scale's sample holder. The electrostatic sensor then determines the electrostatic charge level of the sample. If the sample is electrostatically charged, the data from the electrostatic sensor is transmitted to a measuring unit of the weighing electronics. This unit compares the transmitted data from the electrostatic sensor with a predefined threshold. If this threshold is exceeded, an action is triggered by the weighing electronics. This action can, for example, block further weighing and / or activate the ionizer.Activating the ionizer creates an ion cloud and introduces it into the weighing chamber. This causes the electrostatic charge of the sample to approach its electrostatic neutral state due to recombination of the charges in the ion cloud with the charges of the sample. The duration and intensity of the ionizer operation depend on the determined electrostatic charge level of the sample. The electrostatic charge of the sample is then measured again using the electrostatic sensor. The ionizer is then reactivated if necessary. These steps are repeated until the electrostatic charge of the sample detected by the electrostatic sensor falls below the predefined threshold. This means that the electrostatic neutral state of the sample is detected – within specified tolerances.The actual weighing process then begins. This means that a weight value representative of the electrostatic neutral state of the sample is calculated from the measured values ​​recorded by the weighing sensor. This weight value is ultimately the final weight value that is output.

[0009] The disadvantage of this known device is that the ionizer control requires access to data from a separate electrostatic sensor. This makes the ionizer control, and thus the weighing process as a whole, time-consuming and costly.

[0010] From the aforementioned generic publication, a scale with an ionizer is known that uses the development of the weight values ​​even during the ionizer's activity to draw conclusions about the achievement of the electrostatic neutral state. Specifically, while the ionizer is active, measured values ​​from the weighing sensor are continuously recorded and converted into weight values ​​in a device-specific manner. These weight values ​​are treated as preliminary weight values, and their temporal development is observed. With highly electrostatically charged weighing material, the effect of the ionizer activity is strong, and the preliminary weight values ​​change rapidly. As the charge of the weighing material decreases as a result of the ionizer activity, the preliminary weight values ​​gradually stabilize. Achieved stability of the preliminary weight values ​​within specified tolerances is then interpreted as the achievement of the electrostatic neutral state.The disadvantage, however, is that this approach only works with good, at least qualitative, prior knowledge of the electrostatic state of the weighing sample. If the ionizer is polarized incorrectly, thereby increasing the charge of the weighing sample, the preliminary weight values ​​will also stabilize after some time – namely, when the maximum possible electrostatic charge of the weighing sample is reached. The interpretation of weight value stability as an electrostatic neutral state, as suggested in the publication, is then incorrect.

[0011] EP 2 757 354 A1 does point out the advantages of a priori knowledge of the sign of the weighing sample's charge, particularly for controlling an ionizer in such a way that it sprays the weighing sample exclusively with ions of the "correct" polarity. However, the approach of a special electrostatic sensor, known from the prior art discussed above, is advocated for this purpose. Regarding its disadvantages, reference is made to the above.

[0012] DE 20 2008 017 708 U1 also discloses a scale with an ionizer, which comprises four partial ionizers. The four partial ionizers are activated and deactivated in pairs, controlled by a program in the weighing electronics. The activation of the partial ionizers and their duty cycle are controlled depending on the measured humidity, the opening state of the draft shield, and / or the signal from other sensors. No statement is made about the exact time at which all partial ionizers are deactivated; only that this occurs depending on the measured humidity, the opening state of the draft shield, and / or the signal from other sensors.

[0013] Another disadvantage of this known device is the need for a separate sensor to control the ionizer. This makes controlling the ionizer, and thus the weighing process as a whole, unnecessarily time-consuming and costly. Task

[0014] It is the object of the present invention to provide a method for operating a balance with an ionizer, in which the ionizer is reliably activated during the actual neutralization phase in such a way that it only generates ions that are capable of actually neutralizing the electrostatic charge of the weighing object. Description of the invention

[0015] This object is achieved in conjunction with the features of the preamble of claim 1 in that during a detection phase, positive and negative ion clouds are generated alternately by means of the ionizer, and during a neutralization phase following the detection phase, only an ion cloud of the sign which led to larger changes in the successively calculated, preliminary weighing values ​​in the detection phase.

[0016] Preferred embodiments are the subject of the dependent claims.

[0017] As is generally known from the prior art, the present invention also provides that, when the ionizer is activated, measured values ​​from the weighing sensor are recorded and weight values ​​are calculated from them. However, when the ionizer is activated, only preliminary weight values ​​are initially calculated. Only when a predetermined number of consecutively calculated preliminary weight values ​​are recognized as stable within predetermined limits is the final weight value calculated. The final weight value is ultimately output.

[0018] The invention utilizes the knowledge that the continuously calculated weight value of an electrostatically charged sample is unstable when it interacts with the charges of an ion cloud. As soon as the charges of the ion cloud collide with those of the sample, they recombine, changing the prevailing Coulomb forces and thus the vertical force component that adds up to the weight force acting on the sample. Accordingly, the consecutively calculated weight values ​​of an electrostatically charged sample change when the ionizer is activated. These weight value changes are used to determine the electrostatic charge state of the sample. The final weight value should only be calculated and output when consecutively calculated, preliminary weight values ​​have approximately asymptotically approached a stable value.The stability of consecutively calculated weight values ​​with the ionizer activated indicates that the sample has approached its electrostatic neutral state. Consequently, the final weight value is representative of the sample's electrostatic neutral state and is virtually unaffected by electrostatic charges on the sample. The advantage of this approach is that an additional sensor for detecting electrostatic charges on the sample is unnecessary. Eliminating the sensor makes the process simpler and more cost-effective. Furthermore, the weighing process is shortened compared to other state-of-the-art methods because the steps of data acquisition by a sensor and the evaluation and response to the sensor data are eliminated.

[0019] Typically, the ionizer always generates positive and negative ions simultaneously. This ensures a charge balance of the ion cloud migrating to the sample.

[0020] According to the invention, however, during a detection phase, the ionizer generates alternating positive and negative ion clouds, and during a neutralization phase following the detection phase, only an ion cloud of the sign that led to larger changes in the successively calculated, preliminary weight values ​​during the detection phase is generated. Thus, during a detection phase, the ionizer is operated in such a way that only positive and only negative ion clouds are alternately generated by the ionizer. In this way, the electrostatic charge state of the weighing sample, or more precisely, the sign of the electrostatic charge, can be determined. If the weighing sample is (predominantly) positively charged, interaction with a negatively charged ion cloud causes larger changes in the weight value than interaction with a positively charged ion cloud.Only the charges of the negatively charged ion cloud can recombine with the positive charges of the sample, leading to changes in the prevailing Coulomb forces and thus in the vertical force component that adds to the weight acting on the sample and distorts the weight value. Conversely, if the sample is (predominantly) negatively charged, introducing a positively charged ion cloud into the weighing chamber leads to greater changes in the weight values ​​than introducing a negatively charged ion cloud. Ultimately, only the charges of the positively charged ion cloud can neutralize the negative charges of the sample, which has a greater effect on the acting Coulomb forces and, consequently, on the weight value.

[0021] In a neutralization phase following the detection phase, the ionizer is then operated in such a way that only an ion cloud of the sign that led to significant changes in the preliminary weighing values ​​during the detection phase is generated. This means that during the neutralization phase, the ionizer only generates ions of a specific sign, namely the sign that does not correspond to the electrostatic charge of the weighing sample. Thus, only those ions are generated that are capable of neutralizing the electrostatic charge of the weighing sample. This shortens the operating time required for the ionizer to neutralize the electrostatic charge of the weighing sample and, consequently, the duration of the overall weighing process.

[0022] Preferably, after the stability of the preliminary weight values ​​has been detected and before the final weight value is calculated, the ionizer is deactivated and then further measured values ​​from the weighing sensor are recorded, from which further preliminary weight values ​​are continuously calculated until a predetermined number of these consecutively calculated, further preliminary weight values ​​are recognized as stable within specified tolerances. The ionizer is therefore deactivated as soon as consecutively calculated, preliminary weight values ​​no longer vary. Subsequently, further preliminary weight values ​​are continuously calculated until these also remain stable. Only when this is the case is the final weight value calculated and output. Deactivating the ionizer before calculating the final weight value has the advantage that the final weight value is determined undisturbed by the so-called ion wind, which results from the movement of the ion cloud generated by an activated ionizer.Even if the sample has already approached its electrostatic neutral state, the ion wind influences the weight value – albeit only in the µg range. Accordingly, when operating high-resolution scales, a load jump is noticeable when continuously calculating further preliminary weight values ​​after the ionizer is deactivated. Because the final weight value is only calculated after the ionizer is deactivated and after the subsequent load jump, the output final weight value is even more precise and less influenced by interference factors that impair the accuracy of the weight value.

[0023] Particularly preferably, the final weight value is calculated exclusively from the additional preliminary weight values. In other words, the final weight value should not be calculated from preliminary weight values ​​or from a combination of preliminary and additional preliminary weight values. Instead, the final weight value should be calculated solely from additional preliminary weight values, i.e., those weight values ​​based on the measured values ​​of the weighing sensor with the ionizer deactivated. This ensures that only weight values ​​calculated after the load jump caused by deactivating the ionizer serve as the basis for calculating the final weight value, thereby further increasing the precision of the final weight value.

[0024] Ideally, the weighing chamber is enclosed on all sides by an openable draft shield. This draft shield allows for more precise determination of the weight value, unaffected by environmental influences such as drafts.

[0025] The ionizer is preferably activated by opening the draft shield when the sample holder is unloaded. This means that the ionizer is activated when the draft shield is opened and no load is detected on the sample holder. If the ionizer is activated when the draft shield is opened while the sample holder is free of any sample, electrostatically charged samples can be discharged by the ion cloud generated by the ionizer as they are introduced into the weighing chamber, i.e., before they are placed on the sample holder. This can further reduce the total time required for the weighing process.

[0026] Alternatively, the ionizer can be activated by applying a load to the sample holder. In this case, the ionizer is activated by registering a weight or load on the sample holder. This has the advantage that the ionizer is only activated when it is actually needed—namely, when a sample is actually being weighed. This shortens the ionizer's operating time and, as a result, reduces the waste heat generated by the ionizer's power loss when activated. The latter is advantageous from a weighing perspective, as the ionizer's waste heat can cause undesirable convection currents in the weighing chamber that distort the weight value.

[0027] The ionizer can also be activated by the signal from a proximity sensor that crosses a loading path. The loading path here refers to the path the weighing sample must take when the balance is operated as intended, in order to be introduced into a weighing chamber, possibly separated from the surroundings by an openable draft shield, and placed on the weighing sample holder. Activating the ionizer by the signal from such a proximity sensor is a simple variant to implement. For example, the sensor can be designed as an inductive or optical proximity sensor (e.g., in the form of a light barrier). Depending on the arrangement of the proximity sensor in the loading path, the ionizer can be activated earlier, for example, when the weighing sample is introduced into the weighing chamber, or later, for example, when the weighing sample is placed on the weighing sample holder.

[0028] Alternatively, the ionizer can be activated by an actuatable switch. The switch is preferably located outside the weighing chamber. Particularly preferably, the switch can be located in a control unit for manual or other targeted input (e.g., with the foot) of control commands for scale operation. This allows a user of the method according to the invention to activate the ionizer themselves, if desired.

[0029] In a preferred embodiment of the invention, the ionizer is pulsed on and off in its activated state, and correction terms for mathematically correcting the final weight value are determined from changes in successively calculated, preliminary weight values ​​that occur when the ionizer is off. The activated ionizer is thus alternately switched on and off. If changes occur in successive, preliminary weight values ​​even when the ionizer is switched off, it can be concluded that, in addition to the electrostatic charge of the weighing object, other interfering factors influence the accuracy of the weight value. This is because, when the ionizer is switched off, no ion cloud is generated. Accordingly, no ion cloud can migrate to the weighing object and recombine with the electrostatic charges of the weighing object during this period.Consequently, when the ionizer is switched off, the prevailing Coulomb forces do not change, and the magnitude of the vertical component of this force, which is added to the vertically acting weight force and distorts the weight value, remains the same. Therefore, changes in the preliminary weight values ​​that occur despite the ionizer being switched off must result from other influencing factors, such as temperature fluctuations, material creep of the weighing sensor, or air convection. To ensure the most reliable final weight value possible, correction terms are determined from the described changes in the preliminary weight values, which are not based on an electrostatic charge of the weighing object. These correction terms can be used to mathematically correct the final weight value.

[0030] Further details and advantages of the invention will become apparent from the following specific description and drawings. Brief description of the drawings

[0031] They show: Fig. 1: a schematic representation of a scale for carrying out the method according to the invention, Fig. 2: a first exemplary course of weighing values ​​during the inventive operation of a balance with ionizer according to Fig. 1, Fig. 3a: a second exemplary curve of weighing values ​​during the inventive operation of a balance with a pulsed on and off ionizer, Fig. 3b: a third exemplary course of weighing values ​​during the inventive operation of a balance with pulsed on and off ionizer and Fig. 4: a fourth exemplary course of weighing values ​​during operation of a scale according to the invention, comprising a detection and a neutralization phase. Description of preferred embodiments

[0032] In order to be able to carry out the method according to the invention for operating a scale, a scale is required that has certain features. An example of such a scale that is suitable for carrying out the method according to the invention is shown in Fig. 1. The scale 10 from Fig. 1 comprises a weighing chamber 12, which—although not absolutely necessary for the invention—is bordered on all sides by a draft shield 24. Located within the weighing chamber 12 is a sample holder 14, on which a sample to be weighed can be positioned. To allow sample to be introduced into the weighing chamber 12 bordered by the draft shield 24 and placed on the sample holder 14, the draft shield 24 has at least one openable element, for example, an openable side wall. The sample holder 14 arranged in the weighing chamber 12 is mechanically connected to a weighing sensor 16, which in turn is connected to weighing electronics 20. Measured values ​​are acquired by means of the weighing sensor 16, from which weight values ​​corresponding to the mass of the sample are calculated by means of the weighing electronics 20. The scale 10 further comprises a display 22 by means of which weighing values ​​can be output and displayed.In addition, the balance 10 comprises an ionizer 18, by means of which an ion cloud can be introduced into the weighing chamber 12.

[0033] Fig. 2 shows a first exemplary course of weighing values ​​28 during operation of a scale 10 with ionizer 18, as shown in Fig. 1 is shown. In Fig. 2, at time t1, a stable zero value can initially be seen with the weighing sample holder 14 unloaded. At the moment t2, at which the weighing sample is placed on the weighing sample holder 14, a significant load jump occurs. When the weighing sample is placed on the weighing sample holder 14, the weighing sensor 16 begins to produce measured values, from which preliminary weight values ​​are continuously calculated by the weighing electronics 20. The measured values ​​of the weighing sensor 16 are preferably recorded when it is registered that the weighing sample holder 14 is loaded and the draft shield 24 is closed. However, the recording of the measured values ​​can also be started simply by placing a load on the weighing sample holder 14 or closing the draft shield 24.

[0034] At time t3, the ionizer 18 is activated. In the present example, the ionizer 18 is permanently switched on in its activated state (time period T1), generating both positive and negative ions simultaneously. The activation of the ionizer 18 is noticeable in the electrostatically charged weighing sample through a time-dependent change in the weight values; more precisely, the preliminary weight values ​​decrease over time. This is due to the fact that the ionizer 18 generates an ion cloud, which is introduced into the weighing chamber 12, where the charges of the ion cloud recombine with those of the weighing sample. The recombination, in turn, causes a change in the prevailing Coulomb forces and thus a change in the vertical force component, which, in addition to the weight force acting on the weighing sample, acts on the weighing sample holder 14 and is also detected by the weighing sensor 16. Fig. 2 shows what a possible weighing value curve 28 looks like when the loading of the weighing material holder 14 (time t2) and the activation of the ionizer 18 (time t3) occur at different times, more precisely when the activation of the ionizer 18 only occurs after the loading of the weighing material holder 14. This selected example merely serves to illustrate the effect of ionizer activation on the weighing value curve 28. Preferably, the ionizer 18 is activated by opening the draft shield 24 when the weighing sample holder 14 is unloaded or by the signal of a proximity sensor that crosses a loading path - i.e., before the weighing sample holder 14 is loaded. Likewise, the ionizer 18 can be activated by loading the weighing sample holder 14 (i.e., simultaneously with the loading of the weighing sample holder 14) or by actuating a switch.

[0035] When the ionizer 18 is activated (time period T1), the electrostatic charge state of the electrostatically charged weighing object approaches its electrostatic neutral state, which is noticeable by changes in the preliminary weighing values. Accordingly, the achievement of the electrostatic neutral state of the weighing object within specified tolerances is recognized by a predetermined number of consecutive preliminary weighing values ​​remaining stable, as shown in Fig. 2 is the case at time t4.

[0036] In Fig. 2, a small load jump can also be seen at time t5 after the preliminary weight values ​​have stabilized. This results from the deactivation of ionizer 18. Even if the electrostatic charge state of the weighing sample is already in its neutral state and the charges of the ion cloud generated by ionizer 18 no longer interact with the charges of the weighing sample, the ion wind generated by ionizer 18 nevertheless has an undesirable, distorting effect on the calculated weight values.

[0037] In order not to include this effect on the weight value calculation, as in Fig. 2, after deactivation of the ionizer 18 at time t5, further preliminary weight values ​​are preferably continuously calculated until, as at time t6, a predetermined number of these consecutively calculated, further preliminary weight values ​​remain stable within specified limits. Only then is the final weight value calculated and output—ideally exclusively from the further preliminary weight values.

[0038] In Fig. 3a shows a second exemplary curve of weighing values ​​28' during operation of the scale 10 with ionizer 18. Reference numerals that correspond to those from Fig. 2 correspond to the points in time or time periods there. In contrast to the Fig. 2 is in Fig. 3a shows a weighing value curve 28' in which the ionizer 18 is pulsed on and off in its activated state (time period T1). Fig. 3a the times of ionizer switching on with t 31 and the ionizer switching off with t 32 Is - as in Fig. 3a - the electrostatic charge state of the weighing material is the only disturbing factor present in the weighing chamber 12 which affects the accuracy of the weighing value, the successively calculated, preliminary weighing values ​​change only when the ionizer 18 is switched on, but not when it is switched off.

[0039] However, if - as in the example weight value curve 28" in Fig. 3b shows that, in addition to the electrostatic charge of the weighing sample, at least one other interfering factor is present in the weighing chamber 12 that impairs the precise determination of the mass of the weighing sample (e.g., temperature fluctuations). Changes in successively calculated, preliminary weight values ​​can be detected even when the ionizer 18 is switched off. To minimize the influence of these additional interfering factors on the final weight value, the process variant presented here uses correction terms to determine the weight value changes when the ionizer 18 is switched off, which can be used to mathematically correct the final weight value.

[0040] Fig.Figure 4 finally shows a fourth exemplary curve of weighing values ​​28''' during operation of a scale 10 with ionizer 18. Here, the ionizer operation is divided into a detection phase (time period T2) and a neutralization phase (time period T3). In the detection phase T2, initially only positive or only negative ion clouds are alternately generated by the ionizer 18 and introduced into the weighing chamber 12. The times at which only positive ions are generated are designated by t 33 marked; the times at which only negative ions are produced are marked with t 34In the example shown, the weighing sample is predominantly negatively electrostatically charged, which is why the introduction of positively charged ion clouds into the weighing chamber 12 causes greater changes in the preliminary weighing values ​​than the introduction of 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 weighing value curve 28'''. Accordingly, in a neutralization phase T3, which follows the detection phase T2, only an ion cloud of the sign opposite to the electrostatic charge state of the weighing sample can be generated by the ionizer 18. In this way, the neutralization of the electrostatic charge of the weighing sample and thus the overall duration of the weighing process can be further accelerated.

[0041] Of course, the embodiments discussed in the specific description and shown in the figures represent only illustrative embodiments of the present invention. A person skilled in the art will have a wide range of possible variations available to him in light of the disclosure herein. List of reference symbols 10 scales 12 Weighing room 14 Weighing material holder 16 weighing sensor 18 ionizer 20 Weighing electronics 22 Advertisement 24 Wind protection 28, 28', 28'', 28''' Weight history t1 Zero value with unloaded weighing object t2 Weight value when loading the weighing load holder t3 Weight value curve when activating the ionizer t 31 Weight value curve with ionizer switched on t 32 Weight value history with ionizer switched off t 33Weight value curve when introducing positively charged ion clouds into the weighing chamber t 34 Weight value curve when introducing negatively charged ion clouds into the weighing chamber t4 Weight value curve when the electrostatic neutral state of the weighing material is reached t5 Weight value history when deactivating the ionizer t6 Weight value history after deactivating the ionizer T1 weight value curve when the ionizer is activated T2 detection phase T3 neutralization phase

Claims

[1] Method for operating a scale (10) with a weighing material holder (14) arranged in a weighing chamber (12) for receiving weighing material, a weighing sensor (16) mechanically connected to the weighing material holder (14), an ionizer (18) by means of which an ion cloud can be introduced into the weighing chamber (12), and weighing electronics (20) connected to the weighing sensor (16) and the ionizer (18) for control purposes, comprising the steps: - introducing an ion cloud into the weighing chamber (12) to approximate the electrostatic charge state of the weighing sample - if present - to its electrostatic neutral state by means of the ionizer (18), - Detection of the electrostatic neutral state achieved within specified tolerances and - Recording measured values ​​of the weighing sensor (16), calculating a final weighing value representative of the electrostatic neutral state and outputting the final weighing value, wherein, when the ionizer (18) is activated, measured values ​​of the weighing sensor (16) are continuously recorded, from which preliminary weighing values ​​are continuously calculated, and wherein, after a predetermined number of consecutively calculated preliminary weighing values ​​have been recognized as stable within predetermined tolerances, the final weighing value is calculated and output, characterized by , that during a detection phase, positive and negative ion clouds are generated alternately by means of the ionizer (18), and during a neutralization phase following the detection phase, only an ion cloud of the sign which led to larger changes in the successively calculated, preliminary weighing values ​​in the detection phase. [2] Method according to claim 1, characterized bythat after the stability of the provisional weighing values ​​has been detected and before the final weighing value is calculated, the ionizer (18) is deactivated and subsequently further measured values ​​of the weighing sensor (16) are recorded, from which further provisional weighing values ​​are continuously calculated until a predetermined number of these successively calculated, further provisional weighing values ​​have been detected as stable within predetermined tolerances. [3] Method according to claim 2, characterized by that the final weight value is calculated exclusively from the other preliminary weight values. [4] Method according to one of the preceding claims, characterized by that the weighing chamber (12) is bounded on all sides by an openable draft shield (24). [5] Method according to claim 4, characterized by that the ionizer (18) is activated by opening the draft shield (24) when the weighing sample holder (14) is unloaded. [6] Method according to one of claims 1 to 4, characterized by that the ionizer (18) is activated by loading the weighing material holder (14). [7] Method according to one of claims 1 to 4, characterized by that the ionizer (18) is activated by the signal of a proximity sensor that crosses a feed path. [8] Method according to one of claims 1 to 4, characterized by that the ionizer (18) is activated by an operable switch. [9] Method according to one of the preceding claims, characterized by that the ionizer (18) is switched on and off in a pulsed manner in its activated state, and correction terms for the mathematical correction of the final weighing value are determined from changes in successively calculated, preliminary weighing values ​​occurring when the ionizer (18) is switched off.

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