JP5797081B2 - Weighing system - Google Patents

Description

  The present invention relates to a weighing system.

  In general, a weighing system detects a load by a holding unit in which an object to be weighed is stored or placed by a load detector, and a load signal from the load detector is detected by a weight calculator connected to the load detector. And the weight of the object to be weighed is displayed on a predetermined display unit. In such a weighing system, the zero point and the span coefficient are adjusted in order to suppress a decrease in measurement accuracy due to a change in the internal mechanism over time or a change in the surrounding environment. The zero point adjustment means adjustment so that the display of the weight calculator becomes zero when the load detector is in a no-load state, and the adjustment of the span coefficient corresponds to the load applied to the load detector. This refers to adjusting the slope (span coefficient) of the input / output characteristics of the weight calculator so that the display is correct.

  In Patent Document 1, as an invention related to an electronic balance having a function of determining whether calibration is appropriate, the zero and span coefficients of the electronic balance are set at the time of calibration at the manufacturing stage (adjustment mode) of the electronic balance, and at the time of calibration in the normal mode Whether the zero and span coefficients are obtained using the zero and span coefficients set during calibration in the adjustment mode, and the zero and span coefficients are updated based on the result of comparing the measured values with the allowable values. Is disclosed.

  In Patent Document 2, as an invention relating to a heating cooker, the heating cooker includes a weight sensor that outputs a signal corresponding to the weight of food or the like, and before each start of heating, a signal from the weight sensor is output. It is disclosed that when the signal level is within a predetermined level corresponding to a predetermined weight as viewed from the reference zero point, the reference zero point is changed based on the signal level.

JP 2000-121423 A Japanese Patent Laid-Open No. 2000-18592

  By the way, even when a new weighing system is constructed or when the configuration of an existing weighing system is changed (for example, when a load detector or a weight calculator is replaced), the zero point and span coefficient are adjusted (hereinafter, Zero / span adjustment) is required. However, in Patent Documents 1 and 2, the zero / span adjustment is only performed for the purpose of verifying the temporal change of the internal mechanism and the surrounding environment, and the adjustment is performed when the measurement system is constructed or changed. There is no disclosure or suggestion to implement. Therefore, Patent Documents 1 and 2 do not assume a case where the configuration of the weighing system to be subjected to zero / span adjustment is changed, and also to determine whether the zero / span adjustment value is appropriate. The reference value of the load detector is not set to reflect the load detector condition setting information (performance, specifications, configuration conditions, etc.) that affects the accuracy of zero / span adjustment. Even if it is clarified that it was not appropriate, it is difficult to identify the cause.

  In addition, there are a hopper scale, a conveyor scale, a track scale, and the like as a form that the weighing system can take, and the structure of the weighing system naturally varies depending on these forms. For example, the load cell (load detector) employs a digital output load cell (referred to as a digital load cell) equipped with an analog / digital converter in addition to an analog output load cell (referred to as an analog load cell). There is. In addition to the form using one load cell / weight sensor as in Patent Documents 1 and 2, a form called a multi-load cell using a plurality of load cells may be adopted. In addition, there is no lever for adjusting the load applied to the load cell while supporting the holding part of the object to be weighed, the presence or absence of an explosion-proof unit, or the power supply of the weight calculator as the power source of the excitation voltage applied to the load cell. There are also variations such as using an external power source.

  As described above, there are various types of weighing systems, and it is necessary for workers to make an adjustment after accurately grasping the zero / span adjustment value from these forms. Later, the zero / span adjustment value could not be grasped, which caused a misadjustment. For example, in the case of a weighing system that introduces an explosion-proof unit, an operator adjusts without installing an explosion-proof unit, or in the case of a multi-load cell, incorrectly adjusts the number of load cells connected to the weighing object holder. The case where it performs is assumed. Conventionally, since there is no way to grasp these careless mistakes, the adjustment value deemed appropriate at the time of adjustment does not reflect the configuration of the weighing system at the time of actual operation. There was a risk of problems such as weighing errors.

  The present invention has been made to solve such a problem, and an object of the present invention is to appropriately execute the adjustment reflecting the configuration of the measurement system during actual operation.

  In order to solve the above problems, a weighing system according to an aspect of the present invention includes a holding unit that holds an object to be weighed, and an output signal corresponding to a load by the object to be weighed held by the holding unit. And a weight calculator that calculates the weight of the object to be weighed based on an output signal of the load detector, and the weight calculator is a weighing system including a storage device. The weight calculator is configured to receive condition setting information of the load detector and store it in the storage unit, to obtain an output signal of the load detector, and to obtain the output signal of the load detector. And means for calculating an adjustment reference value based on the condition setting information of the load detector stored in the storage, and a predetermined range in which the acquired output signal of the load detector is defined by the calculated adjustment reference value Whether it fits in And when storing the obtained output signal of the load detector as an adjustment value in the storage unit when it is determined that it falls within the predetermined range, and when it is determined that it does not fall within the predetermined range And a means for outputting a warning signal.

  According to the configuration of the weighing system, the adjustment reference value that is a criterion for determining whether or not the adjustment value is appropriate is calculated by reflecting the condition setting information of the load detector. Reflection can be appropriately performed.

  In the weighing system, the condition setting information of the load detector includes the number, output, and capacity of the load detector, a tare load, and an excitation voltage applied to the load detector, and the adjustment reference value The means for calculating the zero point reference value and / or based on the output signal of the load detector when the load detector is unloaded and the condition setting information of the load detector stored in the storage device Means for calculating a span coefficient reference value may be included.

  According to the configuration of the weighing system, whether the zero point and the span coefficient are appropriate reflecting the number, output, and capacity of the load detector, the tare load, and the excitation voltage applied to the load detector. Since the zero reference value and / or the span coefficient reference value, which are the determination criteria, are calculated, the degree of freedom in the configuration of the weighing system during actual operation to be adjusted increases. In particular, the number of load detectors is reflected in the calculation of the adjustment reference value, and it is possible to use either one load detector or multiple load detectors. It is possible to judge whether the zero / span adjustment is good or bad.

  In the weighing system, the condition setting information of the load detector includes an identifier for identifying whether or not an explosion-proof unit is provided between the holding unit and the load detector and the weight calculator, and the zero point reference The means for calculating the value may apply a calculation formula for the zero point reference value and / or the span coefficient reference value depending on whether or not the explosion-proof unit is provided according to the identifier stored in the storage device.

  According to the configuration of the weighing system, whether the zero / span adjustment is good or not can be determined regardless of whether the explosion-proof unit is provided or not provided. Therefore, the degree of freedom in configuration of the weighing system during actual operation that is the target of zero / span adjustment is further increased.

  In addition to the above, the configuration of the weighing system may be as follows.

  In the weighing system, the load detector condition setting information includes a lever ratio for adjusting a load applied to the load detector, and the means for calculating the zero reference value and the span coefficient uses the lever. In this case, a means for calculating the zero reference value and / or the span coefficient reflecting the lever ratio stored in the storage unit may be included. According to this configuration, the zero reference value and / or the span coefficient are calculated by reflecting the lever ratio for adjusting the load applied to the load detector. Will further increase the degree of freedom.

  In the weighing system, the condition setting information of the load detector is set separately for the case where the load detector is an analog output and a case of a digital output, and the zero reference value and / or the span coefficient is calculated. Applies the zero point reference value and / or the span coefficient calculation formula that differs depending on whether the load detector is an analog output or a digital output according to the condition setting information of the load detector stored in the storage device. It is good also as a means to do. According to this configuration, it is possible to determine whether the zero / span adjustment is good or not regardless of whether the load detector is an analog output or a digital output. Therefore, the degree of freedom in the configuration of the weighing system during actual operation to be adjusted is further increased.

  ADVANTAGE OF THE INVENTION According to this invention, adjustment can be performed appropriately in consideration of the structure of the measurement system at the time of actual operation.

FIG. 1 is a conceptual diagram showing a configuration example of a weighing system according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a mode in which a load applied to the load cell is adjusted using a lever. FIG. 3 is a diagram showing an example of connection between the load cell and the weight calculator via the explosion-proof unit. FIG. 4 is a block diagram showing a configuration example of the weight calculator in the embodiment of the present invention. FIG. 5 is a diagram showing an example of load cell information in the embodiment of the present invention. FIG. 6 is a flowchart showing the flow of zero adjustment in the embodiment of the present invention. FIG. 7 is a flowchart showing the flow of span adjustment in the embodiment of the present invention. FIG. 8A is a diagram for explaining a combined output of the plurality of analog load cells input to the weight calculator when a plurality of analog load cells are provided. FIG. 8B is a diagram for explaining a combined output of the plurality of digital load cells input to the weight calculator when a plurality of digital load cells are provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout the drawings, and redundant description thereof is omitted.

[Configuration example of weighing system]
(Basic configuration)
FIG. 1 is a conceptual diagram showing a configuration example of a weighing system according to an embodiment of the present invention.

  The weighing system shown in FIG. 1 uses a hopper scale that measures the weight of an object to be stored in the weighing hopper as an example. In addition, the weighing system measures the weight of an object to be transported on a conveyor. It may be a conveyor scale to be used, a truck scale for measuring the weight of the vehicle in a state where wheels are mounted on a mounting table, or the like.

  The weighing system shown in FIG. 1 includes a weighing hopper 10, a load cell (load detector) 12, a connection addition box 50, and a weight calculator 20, depending on an object to be weighed contained in the weighing hopper 10. The load applied to the load cell 12 is detected, and the weight calculator 20 connected to the load cell 12 via the connection addition box 50 processes the load signal from the load cell 12 to display the weight of the object to be weighed. Yes.

  The weighing hopper 10 includes a gate 11 for holding and discharging an object to be weighed. The gate 11 is gated according to an opening / closing command from a weighing sequencer (not shown) connected to the weight calculator 20 in a communicable manner. It is driven via a drive mechanism. The weighing hopper 10 is supported by two load cells 12 for weighing an object to be weighed therein. That is, the weighing system shown in FIG. 1 employs a multi-load cell configuration using two load cells 12, but the number of load cells is not limited to two.

  The load cell 12 includes four strain gauges as strain generating bodies, and a so-called Wheatstone bridge circuit is configured by these four strain gauges. The excitation voltage applied to the Wheatstone bridge circuit is normally supplied from an excitation power supply 21 built in the weight calculator 20, but may be supplied from an external power supply unit 40 described later.

  The load cell 12 may be configured as an analog output type analog load cell or a digital output type digital load cell. In the case of a digital load cell, the load cell 12 includes an analog / digital converter. The load cell 12 is connected to the weight calculator 20 via the connection addition box 50. The connection addition box 50 is configured to add the outputs of the load cells 12 in parallel, and the parallel addition value of the outputs of the load cells 12 is input to the weight calculator 20.

(lever)
In addition to the form in which the weighing hopper is supported by the load cell as shown in FIG. 1, there is a form in which the weighing hopper is supported using a lever as shown in FIG. More specifically, a support member 15 in which both right and left ends are supported by a ceiling is constructed, and the weighing hopper 10 is supported by the support member 15. The lever 14 has a fulcrum supported by the ceiling, one end (power point) connected to the center of gravity of the support member 15, and the other end (action point) connected to the load cell 12. Here, in the lever 14, the load applied to the load cell 12 can be appropriately adjusted by appropriately setting the ratio of the length from the fulcrum to one end and the length from the fulcrum to the other end.

(Explosion-proof unit)
In FIG. 1, an explosion-proof unit 30 is shown as an additional component of the metering system. The explosion-proof unit 30 is configured to prevent an excessive voltage or an excessive current from flowing into the hazardous area from the weight calculator 20 installed in the safe area due to a failure of the weight calculator 20 or the like.

  FIG. 3 is a diagram showing an example of connection between the load cell and the weight calculator via the explosion-proof unit. As shown in FIG. 3, for the purpose of supplying an excitation voltage from the weight calculator 20 to the load cell 12, the positive electrode and the negative electrode of the excitation power source 21 of the weight calculator 20 are respectively connected to the load cell 12 via the power supply relay cables 52a and 52b. Are connected to one output terminal OUTA and the other output terminal OUTB of the Wheatstone bridge circuit. The explosion-proof unit 30 incorporates a part of the power supply relay cables 52a and 52b, and a current limiting circuit for limiting an excessive current from the weight calculator 20 on the power supply relay cables 52a and 52b in the explosion-proof unit 30. 31a and 31b are disposed.

  For the purpose of monitoring the excitation voltage applied to the load cell 12 by the weight calculator 20, one output terminal OUTA and the other output terminal OUTB of the Wheatstone bridge circuit of the load cell 12 are connected via sensing relay cables 54 a and 54 b. Thus, one input terminal and the other input terminal of the sensing differential amplifier 22 of the weight calculator 20 are connected. The explosion-proof unit 30 incorporates a part of the sensing relay cables 54a and 54b, and resistors 32a and 32b for suppressing an excessive current are disposed on the sensing relay cables 54a and 54b in the explosion-proof unit 30. Yes.

  Further, in order for the weight calculator 20 to capture the output of the load cell 12, the weight calculator 20 is connected to one output terminal OUTA and the other output terminal OUTB of the Wheatstone bridge circuit of the load cell 12 via signal relay cables 56a and 56b. Are connected to one input terminal and the other input terminal of the signal differential amplifier 23. The explosion-proof unit 30 incorporates part of the signal relay cables 56a and 56b, and resistors 33a and 33b for suppressing excessive current are disposed on the signal relay cables 56a and 56b in the explosion-proof unit 30. Yes.

(External power supply unit)
In FIG. 1, an external power supply unit 40 is shown as another additional component of the metering system. As shown in FIG. 3, an external power supply unit 40 may be used in addition to the excitation power supply 21 built in the weight calculator 20 as a supply source of the excitation voltage applied to the load cell 12. In this case, the positive electrode and the negative electrode of the external power supply unit 40 are connected to one output terminal OUTA and the other output terminal OUTB of the load cell 12 via power supply relay cables 52a and 52b, respectively. When the explosion-proof unit 30 is used, as shown in FIG. 3, a part of the power supply relay cables 52 a and 52 b are taken into the explosion-proof unit 30, and the power supply relay cable 52 a in the explosion-proof unit 30 is used. , 52b are provided with resistors 33a, 33b for suppressing excessive current.

[Configuration example of weight calculator]
FIG. 4 is a block diagram showing a configuration example of the weight calculator shown in FIG.

  The weight calculator 20 includes a sensing differential amplifier 22 and a signal differential amplifier 23, and an analog voltage supplied from the load cell 12 via a connection addition box 50, which serves as an interface with the load cell 12. An analog / digital converter 25 for analog / digital conversion of the parallel addition value of the above, and a storage device for storing a set value of load cell information described later, a program related to measurement (in particular, a zero point and a span coefficient used as program parameters), and the like 26, an operating device 27 for allowing an operator to input setting values of load cell information, which will be described later, and the weight of the object to be weighed obtained based on the load cell output, and work in zero adjustment and span adjustment. Display unit 28 for displaying a message (setting information, warning, etc.) to be notified to a worker, and the above-described measuring sequencer A communication with the communication interface 29 responsible for between a CPU200 for controlling the overall weight calculator 20, a.

  Since the basic function of the weight calculator 20 is to calculate the weight of the object to be weighed based on the output signal of the load cell 12 and output the result, the weight calculator 20 includes the operation unit 27, the display unit 28, The communication interface 29 may not be provided. For example, the load cell information may be input from an external weighing sequencer via the communication interface 29 without providing the operation unit 27. Further, without providing the display device 28, it may be displayed on a display unit of an operation panel incorporating the weight calculator 20 or a display unit of an external weighing sequencer via the communication interface 29. Further, in addition to a form in which a warning to be notified to the worker at the time of zero point adjustment and span adjustment is displayed on the display unit 28, the weight calculator is configured so as to output the warning as sound in order to audibly notify the worker. Reference numeral 20 may include a speaker, and the weight calculator 20 may include a light emitting element to visually notify the worker of the warning. Alternatively, the weight calculator 20 may include an e-mail client and send the warning to a portable device owned by a worker whose e-mail address is registered in advance. The CPU 200 may be configured by a plurality of controllers that perform distributed control in cooperation with each other. For example, the system may be configured such that the CPU is in charge of communication interface processing with a host weighing sequencer, and the DSP is in charge of other processing related to weight calculation.

  FIG. 5 is an example of setting values of load cell information. The load cell information is load cell condition setting information that affects the calculation of the adjustment reference value in zero adjustment and span adjustment. In the example shown in FIG. 5, “number of load cells”, “output of load cells”, “ Examples include load cell capacity, tare load, excitation voltage, explosion-proof mode, lever ratio denominator, and lever ratio numerator.

  In the item “number of load cells”, the number of load cells mounted on a holding unit such as the weighing hopper 10 is set. In the item of “output of load cell”, in the case of an analog load cell, the load cell output is set in mV / V (output voltage (mV) per excitation voltage (V)), and is output in the case of a digital load cell. Set the weight of 1 count with the number of digits below the display unit. For example, when the digital load cell outputs in increments of 0.01 kg with respect to 1 kg, “2” is set. In the “load cell capacity” item, a rated capacity (kg) per load cell is set. For example, when the load cell has a rated capacity of 1 t and is displayed in units of 1 kg, 1000 (kg) is set. In the item of “tare load”, a load (for example, the weight of the weighing hopper 10) applied to the load cell in a state where no object to be weighed is accommodated in the hopper gate 10 and no load is applied by the span adjustment weight is set. In the item “Excitation voltage”, the excitation voltage applied to the analog load cell is set. In the case of a digital load cell, it is not necessary to set the excitation voltage, so “0” is set, for example.

  In the “explosion-proof mode” item, for example, “1” is set when the explosion-proof unit 30 is used, and “0” is set when the explosion-proof unit 30 is not used. In the case of a digital load cell, the explosion-proof unit 30 is not applied. In the items of “lever ratio denominator” and “lever ratio numerator”, the lever ratio denominator and the lever ratio numerator are set when the lever 14 is used, and “0” is set when the lever 14 is not used. Try to set.

  In the case of the present embodiment, the setting of the above load cell information is performed by manual input via the operation unit 27, and the load cell information set by the manual input is stored in the storage device 26. The load cell information stored in the storage device 26 is used when calculating the adjustment reference value. At the time of adjustment, the adjustment reference value calculated from the load cell information is compared with the adjustment value that is actually adjusted, so that the operator can identify abnormalities such as adjustment errors, mechanical interference, load cell defects, etc. It has become.

[Flow of zero adjustment]
FIG. 6 is a flowchart showing the flow of zero adjustment of the weighing system according to the embodiment of the present invention. Note that the zero point adjustment refers to adjustment so that the display of the weight calculator 20 becomes zero when the load cell 12 is in a no-load state as described above.

  First, after making the load cell 12 unloaded, the analog / digital converter 25 performs analog / digital conversion on the analog voltage output from the load cell 12 (step S600). Then, the CPU 200 acquires the current AD conversion value output from the analog / digital converter 25 (step S601). Next, the CPU 200 calculates a zero reference value based on the acquired current AD conversion value and the load cell information stored in advance in the storage device 26 (step S602).

  Then, the CPU 200 determines whether or not the current AD conversion value acquired in step S601 is within a predetermined range defined by the zero reference value calculated in step S602 (step S603). Here, if it is within the predetermined range, the CPU 200 stores the current AD conversion value acquired at step S601 in the storage device 26 as an adjusted zero (step S604). If it is outside the predetermined range, the CPU 200 An error display (warning) indicating that the current AD conversion value acquired in step S601 exceeds the adjustment range is displayed on the display 28 (step S605).

[Span coefficient adjustment flow]
FIG. 7 is a flowchart showing a flow of span coefficient adjustment of the weighing system according to the embodiment of the present invention. Note that the span coefficient adjustment refers to adjusting the gradient (that is, the span coefficient) of the input / output characteristics of the weight calculator 20 so as to display according to the load applied to the load cell 12.

  First, the load of the weight for span adjustment is given to the load cell 12, and the analog / digital converter 25 performs analog / digital conversion of the analog voltage output from the load cell 12. Then, the CPU 200 acquires the current AD conversion value output from the analog / digital converter 25 and the span coefficient adjustment weight value stored in advance in the storage unit 26 (step S700). Next, the CPU 200 calculates the current span coefficient based on the current AD conversion value and the span coefficient adjustment weight value acquired in step S700 (step S701).

  On the other hand, the CPU 200 calculates a span coefficient reference value based on the span coefficient calculated in step S701 and the load cell information stored in advance in the storage device 26 (step S702). Then, the CPU 200 determines whether or not the span coefficient calculated in step S701 is within a predetermined range defined by the span coefficient reference value calculated in step S702 (step S703). Here, if it is within the predetermined range, the CPU 200 stores the span coefficient calculated in step S701 as the adjusted span coefficient in the storage device 26 (step S704). An error display (warning) that the span coefficient calculated in S701 exceeds the adjustment range is displayed on the display 28 (step S705).

[Analog load cell]
(Calculation method of zero reference value)
In the case of an analog load cell, the output voltage Vai of the analog load cell when there is no load is expressed by the following equation.

Here, (Equation 1) will be explained. First, the term (excitation voltage x load cell output) is multiplied by the excitation voltage (V) actually applied to the output voltage (mV / V) per excitation voltage of the analog load cell. It represents the output voltage of the analog load cell at the time of weighing (maximum weight). For example, when the weighing is 1000 kg, the output of the analog load cell is 2 mV / V, and the excitation voltage is 10 V, the output voltage of the analog load cell at the weighing is 20 mV / 1000 kg.

  Next, in the case of a multi-load cell, as shown in FIG. 8A, a plurality of analog load cells are connected in parallel. Therefore, the same excitation voltage is applied to each of the plurality of analog load cells, and the weighing is uniformly distributed to each of the plurality of analog load cells. In the numerical example shown in FIG. 8A, in the case of a multi-load cell using four analog load cells each having an output of 2 mV / V, four analog load cells are applied with an excitation voltage of 10 V applied thereto. When weighing 96t (rated capacity) is applied to the entire load cell, the combined output voltage of the four analog load cells during weighing is 20 mV / 96t. Each of the four analog load cells is multiplied by 24t obtained by dividing the weight 96t by the number of analog load cells. For this reason, in (Equation 1), the number and capacity of analog load cells are divided.

  Next, in consideration of the case where the lever 14 as shown in FIG. 2 is used, in (Equation 1), (lever ratio numerator / lever ratio denominator) is multiplied. Moreover, in (Formula 1), the load (tare load) by the holding | maintenance part (a container, a mounting stand etc.) which four analog load cells support is multiplied.

  Thus, (Equation 1) is derived. Then, using (Expression 1), the output (AD conversion value) Cai of the analog / digital converter 25 when there is no load, that is, the zero reference value is expressed by the following expression.

By applying (Equation 1) and (Equation 2), a criterion for determining whether the zero point is appropriate reflecting the number, output, and capacity of the load cell, the tare load, and the excitation voltage applied to the load cell. Since the zero reference value is calculated, the degree of freedom in configuration of the weighing system during actual operation that is the target of zero adjustment is increased. In particular, the number of load cells is reflected in the calculation of the zero reference value, and zero adjustment is performed regardless of whether one load cell is used or a so-called multi-load cell in which a plurality of load cells are used. Can be determined. Further, according to (Equation 1) and (Equation 2), when a lever that adjusts the load applied to the load cell is employed, the zero reference value is calculated by reflecting the lever ratio in addition to the load cell information. Therefore, the degree of freedom in the configuration of the weighing system during actual operation that is the target of zero adjustment is further increased.

(Span coefficient reference value calculation method)
First, the voltage change (mv) corresponding to the weight value of the span adjustment weight is calculated by the following equation.

(Expression 3) is substantially the same as (Expression 1) except that the tare load in (Expression 1) in the case of zero adjustment is replaced with a weight value. Using this (Equation 3), the span coefficient reference value in the case of an analog load cell is calculated by the following equation.

In (Expression 4), the value obtained by multiplying the weight value by the actual sensing voltage is divided by the AD conversion value corresponding to the weight value and the AD conversion value in mV units. The coefficient reference value is used.

  As described above, the span coefficient reference value is calculated as a criterion for determining whether or not the span coefficient is appropriate, reflecting the number, output, and capacity of the load cell and the excitation voltage applied to the load cell. This increases the degree of freedom in the configuration of the weighing system during actual operation to be adjusted. In particular, the number of load cells is reflected in the calculation of the span coefficient reference value, and the span is applied regardless of whether one load cell is used or a so-called multi-load cell in which a plurality of load cells are used. It is possible to determine whether the coefficient adjustment is good or bad. Furthermore, as with the zero point reference value, the zero point reference value is calculated by reflecting the lever ratio that adjusts the load applied to the load cell. It will increase further.

(When an explosion-proof unit is installed)
As shown in FIG. 3, when the explosion-proof unit 30 is provided, resistors 32a and 32b for current limiting are provided on the sensing relay cables 54a and 54b, and on the signal relay cables 56a and 56b. Are provided with resistors 33a and 33b for current limiting. For this reason, the amplification degree of the differential amplifier for sensing 22 and the differential amplifier for signal 23 changes. Therefore, whether or not the explosion-proof unit 30 is installed is identified by the presence or absence of the “explosion-proof mode” in the load cell information stored in the storage device 26. The zero reference value and the span coefficient reference value are calculated taking into account changes in the amplification degree of the dynamic amplifier 22 and the signal differential amplifier 23. Specifically, the zero point reference value is calculated by multiplying a proportionality constant representing the attenuation of the amplification degree according to the resistance values of the resistors 32a, 32b, 33a, and 33b in (Equation 2). Similarly, the span coefficient reference value is calculated by multiplying a proportionality constant representing the amount of attenuation of the amplification according to the resistance values of the resistors 32a, 32b, 33a, and 33b in (Equation 4).

  As described above, the calculation formulas for the zero point reference value and / or the span coefficient reference value that differ depending on whether or not the explosion-proof unit 30 is provided are applied. Therefore, in any case where the explosion-proof unit 30 is provided or not provided. Even if it exists, the quality determination of zero point adjustment and / or span coefficient adjustment is possible. Therefore, the degree of freedom in the configuration of the weighing system during actual operation to be adjusted is further increased.

[Digital load cell]
(Calculation method of zero reference value)
The zero reference value in the case of a digital load cell is calculated by the following equation.

In the case of a digital load cell, unlike an analog load cell, an AD conversion value corresponding to a load is output as it is. In the case of a multi-load cell, it is an added value of a plurality of digital load cell outputs. For example, when the numerical example shown in FIG. 8B is used, when the weighing 96t (rated capacity) is applied to the four digital load cells as a whole, the combined output of the four digital load cells becomes an AD conversion value corresponding to the weighing 96t. In other words, each of the four digital load cells takes 24t obtained by dividing the weight 96t by the number of load cells. Therefore, the combined output of the four digital load cells is an added value of the AD conversion value corresponding to 24t, that is, an AD conversion value corresponding to the weighing 96t.
(Span coefficient reference value calculation method)
The span coefficient reference value is calculated by the following equation.

In (Expression 6), the case where the lever 14 is used is taken into consideration, and the load cell output when the weight is mounted is divided by the weight value, and this result is used as the span coefficient reference value.

  As described above, the load cell information is set separately when the load cell is an analog output and when the load cell is a digital output, and the calculation formulas for the zero reference value and the span coefficient reference value are different for the analog load cell and the digital load cell. Whether or not analog load cells or digital load cells are used, it is possible to determine whether the zero point adjustment and the span coefficient adjustment are good or bad. Therefore, the degree of freedom in configuration of the weighing system during actual operation to be adjusted is further increased.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  The present invention is useful for adjusting a metering system that can take a variety of forms.

DESCRIPTION OF SYMBOLS 10 ... Measuring hopper 11 ... Gate 12 ... Load cell 14 ... Lever 15 ... Support member 20 ... Weight calculator 21 ... Excitation power supply 22 ... Differential amplifier 23 for sensing ... Signal differential amplifier 24 ... Load cell interface 25 ... Analog / digital converter 26 ... Memory 27 ... Operator 28 ... Display 29 ... Communication interface 30 ... Explosion-proof units 31a, 31b ... current limiting circuits 32a, 32b, 33a, 33b ... resistance 40 ... external power supply unit 50 ... connection addition box 52a, 52b ... power supply relay cables 54a, 54b ... Sensing relay cables 56a, 56b ... Signal relay cables

Claims (3)

A holding unit for holding the object to be weighed, a load detector for outputting an output signal corresponding to a load by the object to be weighed held by the holding unit, and an output signal of the object to be weighed based on the output signal of the load detector. A weight calculator for calculating weight, the weight calculator being a weighing system including a storage device,
The weight calculator is
Means for receiving condition setting information of the load detector and storing it in the memory;
Means for obtaining an output signal of the load detector;
Means for calculating a zero reference value based on the acquired load detector output signal when the load detector is unloaded and condition setting information of the load detector stored in the storage;
Means for determining whether or not the acquired output signal of the load detector is within a predetermined range defined by the calculated zero reference value when the load detector is unloaded ;
When it is determined that it falls within the predetermined range, the obtained output signal of the load detector is stored as an adjustment value in the storage device, and when it is determined that it does not fall within the predetermined range, a predetermined warning signal is output. Means ,
The load detector condition setting information includes a number, output, and capacity of the load detector, a tare load, and an excitation voltage applied to the load detector . The condition setting information of the load detector includes an identifier for identifying whether or not an explosion-proof unit is provided between the holding unit and the load detector and the weight calculator,
2. The measuring system according to claim 1 , wherein the means for calculating the zero reference value applies a calculation formula for the zero reference value that differs depending on whether or not the explosion-proof unit is provided according to the identifier stored in the storage device. . A holding unit for holding the object to be weighed, a load detector for outputting an output signal corresponding to a load by the object to be weighed held by the holding unit, and an output signal of the object to be weighed based on the output signal of the load detector. A weight calculator for calculating weight, the weight calculator being a weighing system including a storage device,
The weight calculator is
Means for receiving condition setting information of the load detector and storing it in the memory;
Means for obtaining an output signal of the load detector;
Means for calculating a span coefficient based on the obtained output signal of the load detector and a value of the span coefficient adjustment weight when a load is applied to the load detector by a span coefficient adjustment weight;
Means for calculating a span coefficient reference value based on the calculated span coefficient and the condition setting information of the load detector stored in the storage;
Means for determining whether the calculated span coefficient falls within a predetermined range defined by the calculated span coefficient reference value;
Means for storing the calculated span coefficient as an adjusted span coefficient in the storage unit when it is determined that it falls within the predetermined range, and outputting a predetermined warning signal when it is determined that the span coefficient does not fall within the predetermined range; And including
Condition setting information of the load detector, the number of the load detector comprises an output, and a capacitor, an excitation voltage applied to the load detector, weighing system.