JP4087976B2 - Electronic scale for detecting electrical disturbance noise - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for detecting electrical disturbance noise, and more particularly to an apparatus configured to be able to detect electrical disturbance noise using an existing sensor in an electronic balance.
[0002]
[Prior art]
In so-called electronic balances such as an electromagnetic balance type weighing device or load cell type weighing device called an electronic balance, a physical quantity such as temperature is measured, and the measurement value is corrected using this measurement result, thereby achieving more accurate measurement. Configured to get a value.
[0003]
Since the electronic scale has a configuration in which an electric signal is processed to obtain a measurement result, if there is an electrical disturbance noise, this greatly affects the calculation of the measurement value, and the reliability of the measurement value decreases. Further, the temperature data output as a result of measuring the physical quantity also outputs a value different from the actual physical quantity due to the electrical disturbance noise, and as a result, correction is performed with an incorrect correction value. As described above, in an electronic scale that inputs and outputs various data and constitutes a complex arithmetic circuit, electrical disturbance noise is a serious factor that impairs the reliability of the apparatus.
[0004]
Electric disturbance noises and their sources vary widely and differ depending on the environment in which the electronic scale is placed. For example, electromagnetic waves emitted from the plugs of vehicle engines, electrostatic discharge noises, It is often used in an environment where many electric noises such as power source noise of devices, I / O signal noise, and recently electromagnetic wave noise due to use of mobile phones act as disturbances.
[0005]
[Problems to be solved by the invention]
Conventionally, the following countermeasures have been implemented for such electrical disturbance noise, but all have their merits and demerits, and particularly have problems in terms of complexity and cost increase of the apparatus.
(A) A method of conducting a conductive treatment inside the case when the case of the device is formed of plastic or the like.
This method has a drawback that the manufacturing cost of the apparatus becomes high.
(B) Design a wiring pattern that reduces the influence of electrical disturbance noise.
This method requires a great amount of labor for designing the wiring pattern, and the influence of noise cannot be completely eliminated.
(C) Design the mounting of each component so as to reduce the influence of electrical disturbance noise.
This method also has the same problem as the above (b).
(D) Noise is absorbed or eliminated by using electronic components, such as providing a noise filter in the power input section or a noise filter in the I / O signal section.
This method is quite effective in terms of noise prevention, but increases the cost.
As described above, each method has advantages and disadvantages, and even if these methods are used, it is practically extremely difficult to completely remove the electrical disturbance noise.
[0006]
[Means for Solving the Problems]
In order to prevent the influence of electrical disturbance noise in the above-mentioned problems, the present invention is configured from the viewpoint that the apparatus becomes complicated and expensive and it is extremely difficult to completely prevent the influence. It is configured to detect the presence or absence of electrical disturbance noise, evaluate the measured value when noise is detected, and display the measurement result (including unmeasurable state) according to the evaluation The detection of electrical disturbance noise is a device configured to detect electrical disturbance noise by using a signal output from an existing sensor in the device without installing any means for detecting noise. is there.
[0007]
That is, a sensor previously installed in the weighing device for detecting physical quantities such as a temperature sensor, a humidity sensor, and a pressure sensor, a means for monitoring a change in a signal output from the sensor, and a change in the signal is a sensor. Means for determining whether there is a change due to a change in a measured physical quantity or a change due to an electrical noise, thereby detecting the presence or absence of electrical noise by determining a change in a signal output from an existing sensor. It is the apparatus which comprised, It is characterized by the above-mentioned.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
For electronic balances, measure physical quantities such as temperature, humidity, and pressure in the environment where a weighing device such as a temperature sensor, humidity sensor, or pressure sensor that measures atmospheric pressure is placed, or the temperature of a specific component in the device A sensor that measures changes is installed. In particular, in an electronic scale, the temperature coefficient of the measured load value is large as follows. Therefore, a temperature sensor is necessarily provided for temperature correction.
(1) Temperature coefficient of magnetic flux density of magnet part of electromagnetic balance type weighing device −200 ppm / ° C. to −300 ppm / ° C.
(2) The span temperature coefficient of the load cell portion of the load cell type weighing device is about +600 ppm / ° C.
[0009]
For example, the temperature sensor detects the temperature in the environment where the electronic balance is arranged, outputs the detection result as an electric signal (many of which are output as a change in voltage), and then A / D-converts the temperature data. Thus, the central processing unit of the apparatus uses the temperature data as the correction value for the load measurement value, and outputs the temperature-corrected value as the load measurement value.
[0010]
In this case, the central processing unit is provided with a noise detection unit having a function of determining the presence / absence of electric noise from the temperature data signal output from the temperature sensor, and when electric noise is detected in the temperature signal, the electric noise is detected. A signal with noise is output to the calculation unit. The calculation unit uses this signal to determine the degree of noise, for example, to reduce the number of digits of guaranteed accuracy of the measurement value, or to output a display with noise to the display unit, so that the weighing device is affected by electrical noise. Display to inform the user that
[0011]
There are several methods for detecting the presence or absence of electrical noise from the temperature data output from the temperature sensor, as described below, and it is also possible to adopt a method using a combination of these methods. If there is electrical noise, this noise will affect each part including the calculation part that calculates the load.However, the present invention is based on the electrical signal output from the temperature sensor as one of the effects of noise. In view of this, the presence / absence of electrical noise is determined by digital processing from the change in the temperature detection signal.
[0012]
Since the signal from the temperature sensor naturally outputs the change in the environmental temperature measured by the sensor, the change in the temperature corresponding to the change in the temperature detection signal is actually observed in the environment where the electronic scale is used. It is determined whether or not the temperature change is likely to occur. For example, when a peak waveform in which the temperature changes by several degrees Celsius in a short time (for example, about 15 seconds) is generated in the temperature detection signal, the actual environmental temperature cannot cause such a change. It can be determined that the waveform is electrical noise. In this case, if the peak waveform ends and becomes a temperature detection signal in a changed state before the peak waveform is formed, the temperature signal at this waveform can be canceled and temperature correction can be performed.
[0013]
Further, when the temperature detection signal rises rapidly in a short time, the presence or absence of electrical noise can be determined from the rise temperature and the rise time. For example, it is empirically known that a value output as temperature data from a temperature sensor in response to a change in environmental temperature does not change more than 0.01 ° C. per second. This is because when the temperature sensor is installed inside the electronic balance, the electronic balance has a certain heat capacity. Therefore, when the change in temperature data per unit time exceeds the above change rate, it can be determined that the temperature detection data is affected by electrical noise.
[0014]
Further, in parallel with the detection signal of the temperature sensor, the presence / absence of electrical disturbance noise can also be determined by determining the detection signal of another sensor, for example, an atmospheric pressure sensor. Incidentally, in some electronic scales, in order to be affected by the buoyancy due to the air of the weighed item, some apparatuses use a barometric pressure sensor and use the measured barometric pressure to correct the buoyancy. Since such a temperature sensor, an atmospheric pressure sensor, and the like measure different physical quantities, changes in measured values of different sensors are basically unrelated. In such a situation, if the changes in measurement data by different sensors are the same and the same change, it is determined that the change has been caused by electrical disturbance noise on the electrical signal output from each sensor. Judge that there is electrical disturbance noise. The method of comparing and judging signals from a plurality of different sensors is more accurate in detecting the presence or absence of electrical disturbance noise.
[0015]
【Example】
Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a block diagram of an electronic balance showing the basic configuration of the present invention. A load signal W output from a load sensor 1 such as a load cell or an electric output unit for a magnet of an electromagnetic balance unit is output to a temperature correction unit 3 as load data WD in a weight A / D conversion unit 2.
[0016]
On the other hand, the temperature sensor 4 measures the environmental temperature of the electronic scale, and this temperature signal t is output to the temperature correction unit 3 and the noise detection unit 6 as temperature data TD in the temperature A / D conversion unit 5. In this noise detection unit 6, it is determined whether or not the temperature data TD is affected by electrical noise by a method described in detail later, and when it is determined that the temperature data TD is affected by electrical disturbance noise. Outputs the noise signal NZ to the calculation / display processing unit 7. The calculation / display processing unit 7 displays on the display unit 8 a carry of the measured value of the load, a display with noise, and the like according to a predetermined method corresponding to the noise signal NZ. In this case, the calculation / display processing unit 7 can also be configured to evaluate the strength of the electrical disturbance noise in response to the noise signal and perform display corresponding to this. When no noise is detected by the noise detection unit 6, the temperature correction unit 3 obtains correction data WDa from the temperature data TD, and the calculation / display processing unit 7 obtains a display value Wd using the correction data WDa. This is displayed on the display unit.
[0017]
FIG. 5 shows an example of the configuration of the noise detector 6 described above, FIG. 2 shows a first example of a method for detecting the presence or absence of electrical disturbance noise from changes in temperature data TD, and FIG. 3 shows a second example. Furthermore, FIG. 4 shows a method for detecting electrical disturbance noise by comparison with other data.
[0018]
First, the outline of the noise detection method will be described with reference to FIGS. First, in FIG. 2, the temperature change detected by the temperature sensor 4 is digitally output as temperature data TD via the temperature A / D unit 5. That is, the temperature data TD corresponds to time, and for example, it is assumed that the temperature data TD is output as a peak as shown in Δti1 between time ti1 and time ti2. In a room where an electronic scale is placed, the normal temperature change cannot change with a short-time peak, except during abnormal operation such as abnormal operation of the air conditioning equipment, such as switching to extreme cooling after cooling. . Further, if the time Δti1 where the peak occurs is a short time such as 15 seconds, for example, such a temperature change does not occur even if the abnormal operation is performed.
[0019]
From the above points, it is determined that the change peak of the temperature data TD is not due to an actual temperature change but due to electrical disturbance noise, and a noise signal NZ is generated. Note that the presence / absence of noise is determined from both the time Δti1 when the peak occurs and the change amount ΔTD of the temperature data TD. Further, the values of the time Δti1 and the temperature data change amount ΔTD as threshold values for determining the presence or absence of electrical disturbance noise are set from actual measured values of actual temperature changes. The measured temperature change rate per unit time (indicated by the symbol K) is a measured value of K ≦ 0.01 ° C./second for reference.
[0020]
Reference numeral L1 indicates a relationship with the time Δti2 required for the actual temperature change when the temperature change rate K is maximum, that is, when the change amount of the temperature data TD is ΔTD1 shown in the figure. Therefore, when the change time Δti1 of the temperature data change amount ΔTD1 and the time Δti2 are Δti1 <Δti2, it is determined that the change peak is not caused by the temperature change but is influenced by the electrical disturbance noise. The noise that generates such a peak is a noise that occurs relatively frequently, such as noise caused by turning on a switch of various electric products, or starting of an electric motor.
[0021]
FIG. 3 shows an example of a method for determining the presence / absence of electrical disturbance noise from another example of change in temperature data TD. In this example, the temperature data TD shows a change that rises at time ti3 and becomes almost stable at time ti4. Such a change pattern itself of the temperature data TD is often seen even in an actual temperature change due to use of a heating device or the like. Accordingly, it is extremely important to determine the presence or absence of electrical disturbance noise from such changes in the temperature data TD in actual use of the electronic scale. By the way, since the temperature change that shows the peak is not usually considered from the arrangement environment of the electronic scale, if a peak occurs as shown in FIG. 3, the presence or absence of noise is determined by assuming that all the peaks are due to electrical disturbance noise. It is also possible to simplify the software.
[0022]
In the change pattern of FIG. 3, what is particularly important in determining the presence or absence of noise is the relationship between the change amount ΔTD2 of the temperature data TD and the time Δti3 required for the change. When evaluated using the temperature change rate K, the shortest time for the change amount ΔTD2 of the temperature data TD is Δti4 corresponding to the change model indicated by the line L2, and the time Δti3 from the time ti3 to ti4 should be Δti3 <Δti4. For example, the change ΔTD2 in the temperature data TD is determined not to be due to an actual temperature change but to an electrical disturbance noise.
[0023]
The change of the temperature data TD shown in FIG. 2 and FIG. 3 has been described by taking the measurement data of the temperature of the environment where the electronic balance is installed as an example. In addition, for example, the temperature of the electromagnetic part is also detected and used as a correction value. Therefore, in the case of a device in which a temperature sensor is installed in the electromagnetic part, if the temperature data of the temperature sensor that measures the environmental temperature and the temperature data from the temperature sensor arranged in the electromagnetic part are used in combination, the electrical data is more likely The presence or absence of disturbance noise can be determined.
[0024]
FIG. 4 shows a noise determination method by still another means. The upper graph of FIG. 4 shows the change of the temperature data TD with respect to the time ti, and the lower graph shows the change of the pressure (atmospheric pressure) data PD with respect to the time ti. Since each data is always data indicating a change in a different physical quantity, there is basically no correlation between the changes. In the example shown in the figure, the temperature data TD and the pressure data PD change independently of each other until time ti4. However, at time Δti5 from time ti4 to time ti5, the change pattern is almost the same, and after time ti5, a different change pattern is taken.
[0025]
As described above, when different physical quantities are independent events, it is virtually impossible for each physical quantity to change in the same time Δti4. Therefore, changes in the data TD and PD at this time Δti4 are detected. It can be determined that both data are affected by electrical disturbance noise, not due to actual physical quantity changes. By comparing and determining measurement data output from a plurality of sensors in this manner, it is possible to determine the presence or absence of electrical disturbance noise with higher accuracy. In this case, the method of determining the presence / absence of electrical disturbance noise by obtaining the rate of change of data per unit time shown in FIGS. 2 and 3 can be used together with this method.
[0026]
FIG. 5 shows an example of the configuration of a noise detector configured to implement the electrical disturbance noise detection method described above. The illustrated example shows a configuration example in the case where the data of the electrical disturbance noise detection target is only the temperature data TD. By the way, since the electronic balance currently used is often used only in consideration of temperature as a physical quantity of the electronic balance arrangement environment, the configuration for detecting electrical disturbance noise only from the temperature data TD is the most usable range at present. It can be said that it is a wide structure.
[0027]
In the figure, the temperature data TD output from the temperature A / D unit 5 is output to the temperature correction unit 3 and also input to the temperature change check unit 9 of the noise detection unit 6. The temperature change check unit 9 checks the temperature data TD every unit time (for example, 1 second), and checks whether the change of the temperature data TD is within the temperature change ratio K described above. When the change of the temperature data TD exceeds the temperature change ratio K, the timer 10 is turned on and time data is output to the change pattern storage unit 11. The change pattern storage unit 11 stores changes in the temperature data TD when the timer 10 is turned on. That is, the change in the temperature data TD is stored in the change pattern storage unit 11 as a change in the temperature data TD with respect to the time data ti as shown in FIG.
[0028]
On the other hand, the temperature change limit value storage section 12 is based on the temperature change ratio K described above, and the actual temperature change amount and the temperature change limit value consisting of the shortest time to reach the change amount (in FIG. A diagram L2 in FIGS. L1 and 3 is stored. The comparison unit 13 compares the change pattern of the temperature data TD with respect to the time data ti of the temperature data TD output from the change pattern storage unit with the limit value data output from the temperature change limit value storage unit 10, and the temperature data When it is determined that the TD change pattern is due to an actual temperature change and is determined not to be due to an actual temperature change, that is, due to electrical disturbance noise, the noise signal NZ is sent to the arithmetic / display processing unit 7. To emit.
[0029]
The calculation / display processing unit 7 increases the number of digits of the numerical value displayed as the display value Wd by the noise signal NZ, or displays on the display unit that the load measurement value cannot be displayed as “electric disturbance noise exists”. To do. The change amount ΔTD of the temperature data TD basically corresponds to the magnitude of the electrical disturbance noise. Therefore, if the change amount ΔTD of the temperature data TD is superimposed on the noise signal NZ, the calculation / display processing unit 7 In accordance with the magnitude of the external disturbance noise, increase the number of digits displayed as the display value Wd, or evaluate whether the load measurement value cannot be displayed as “electric disturbance noise exists”, etc. Can be done.
[0030]
Further, when the electrical disturbance noise is detected, but the generation time of the electrical disturbance noise is short, the temperature data TD due to this electrical noise is removed, and the temperature data due to the electrical disturbance noise is removed in the averaging processing unit 14. It is also possible to output the temperature data TD ′ obtained by averaging the temperature data TD after removing the TD, and use the temperature data TD ′ as data for calculating the correction data WDa.
[0031]
Next, a method for detecting electrical disturbance noise and a correction method using the load data WD will be specifically described with an electronic balance (load cell type balance) having specific performance as an example.
For example, when the electronic scale having a weight of 6 kg has a minimum scale of 0.1 g, the load data WD before temperature correction is 60,000 counts (hereinafter referred to as “cnt”). The temperature data TD is set to 300,000 cnt at 25 ° C. as an example in the temperature environment (10 ° C. to 40 ° C.) where the electronic balance is arranged. Each data with respect to temperature has the following characteristics.
Load data WD: +600 ppm / ° C
Temperature data TD: + 4700ppm / ° C
[0032]
Under the above conditions, when the environmental temperature changes by 1 ° C., each value changes as follows. Load data WD is
WD = 60,000 cnt × (+600 ppm / ° C.) = + 36 cnt / ° C.
The temperature data TD is
TD = 300,000 cnt × (+4700 ppm / ° C.) = + 1410 cnt / ° C.
Therefore, the change of the load data WD with respect to the temperature change can be expressed by the following equation.
(+1410 cnt / ° C.) ÷ (+36 cnt / ° C.) = 39 cnt
That is, the load data WD indicates that 1 cnt correction is applied to the temperature change 39 cnt. In other words, when the temperature data TD changes by 39 cnt due to a factor other than the temperature change, the weight value Wd is displayed erroneously by 1 cnt.
[0033]
Here, regarding the change ΔTD for one second of the temperature data TD, if the change in the actual environmental temperature is 10 cnt / sec at the maximum, if ΔTD ≧ 10 cnt, the change ΔTD is not due to the change in the actual environmental temperature. It can be determined that this is due to electrical disturbance noise.
However, since the temperature change with respect to 1 cnt of the weight value Wd is 39 cnt in the above-mentioned electronic balance, the determination of the electrical disturbance noise with respect to the change ΔTD of the temperature data on the basis of 10 cnt is a correction in this electronic balance. Not appropriate.
[0034]
In the above case, in consideration of the actual use state of the electronic scale, when the load data WD changes by 2 cnt, that is, the change ΔTD of the temperature data is based on 78 cnt (39 cnt × 2), ΔTD ≧ A (A = 78 cnt), it is determined that there is an electrical disturbance noise. When the weight value Wd changes by 1 cnt, that is, based on A = 39 cnt, the presence / absence of electrical disturbance noise can be determined.
[0035]
FIG. 6 is a flowchart showing the above procedure. In the figure, the temperature data TD (S1) output from the temperature A / D unit 5 is compared with the reference temperature change A (S2), and the change ΔTD is larger than the reference temperature change A. In some cases, it is determined that there is an electrical disturbance noise as it is, or since the change is in a short time, it is determined whether the noise part is removed and the temperature data TD is averaged (S3). In this case, averaged temperature data TD ′ is obtained (S4), correction data WDa is created (S5), and the weight value Wd is displayed (S9). On the other hand, when processing is performed in the presence of electrical disturbance noise (S6), correction data WDa is created from temperature data TD mixed with electrical disturbance noise (S10). Thereafter, the display digit number of the load measurement value Wd is changed according to the amount of electrical disturbance noise (S7a), or displayed when the load cannot be displayed, such as “There is electrical disturbance noise”. Display is performed (S7b).
[0036]
When the amount of change ΔTD is smaller than the reference temperature change A in S2, it is determined that there is no electrical disturbance noise, the temperature data TD is taken in (S8), and correction data Wda is created from this temperature data TD ( S5) The weight value Wd is displayed (S9).
[0037]
Although the above description has mainly focused on the determination of the presence or absence of electrical disturbance noise, the following configuration can be added to the present invention.
First, the wiring that connects the sensor unit such as the temperature sensor and the processing unit including the A / D conversion unit is extended beyond the length required for the design, and this portion is used as an antenna to reduce electrical disturbance noise. Increase detection sensitivity.
[0038]
In addition, there are a plurality of wires connecting the sensor unit and the processing unit, one wire is a wire that is electromagnetically sealed as much as possible, and the other is intentionally provided with a high resistance to the above method and sensor output. It is assumed that the detection sensitivity of the electrical disturbance noise is high by increasing the sensor output impedance. With this configuration, if the temperature data TD purely reflects the temperature change, the data passing through both wires is the same, and conversely, the data passing through the sealed wires and the detection of electrical disturbance noise. If there is a significant difference between the data via the wiring with high sensitivity, it can be determined that there is electrical disturbance noise based on this difference. In this case, although it depends on the degree of the sealing effect, it is also possible to take in data as a correction value via the wiring with the seal.
[0039]
【The invention's effect】
As described in detail above, the present invention makes it possible to detect the presence or absence of electrical disturbance noise using an existing sensor in an electronic scale, so there is no need to install a special sensor as in the prior art. However, it is possible to perform highly accurate detection that is not inferior to a noise detection sensor.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic balance showing an embodiment of the present invention.
FIG. 2 is a diagram of changes in temperature data TD showing an example of a method for detecting electrical disturbance noise in changes in temperature data TD at time ti.
FIG. 3 is a diagram of changes in temperature data TD showing another example of a method for detecting electrical disturbance noise in a change pattern of other temperature data TD at time ti.
FIG. 4 is a diagram of a change in temperature data TD showing a method of detecting electrical disturbance noise from a change pattern of temperature data TD and pressure data PD at time ti.
FIG. 5 is a block diagram illustrating a configuration example of a noise detection unit.
FIG. 6 is a flowchart showing an example of a method for detecting electrical disturbance noise.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Load sensor 2 Weight A / D part 3 Temperature correction part 4 Temperature sensor 5 Temperature A / D part 6 Noise detection part 7 Calculation / display processing part 8 Display part 9 Temperature change check part 10 Timer 11 Change pattern memory | storage part 12 Temperature change Limit value storage unit 13 Comparison unit 14 Averaging processing unit TD Temperature data TD 'Averaged temperature data NZ Noise signal WD Load data WDa Correction data Wd Weight display value

Claims (5)

A means for calculating and displaying load data in an electronic balance that electrically outputs load data of a weighing object, measures a physical quantity such as temperature with a sensor, and uses the measured physical quantity data as a correction value for load data calculation. A means for outputting correction data corresponding to the physical quantity data, a detection means for detecting electrical disturbance noise from the physical quantity data, and a calculation part for calculating the load of the weighing object using the correction data. Is an electronic scale for detecting electrical disturbance noise, characterized in that the display value of the calculated load is adjusted in accordance with the presence or absence of electrical disturbance noise or the display with electrical disturbance noise is displayed. . The sensor for measuring the physical quantity is a temperature sensor, and the detection means for detecting electrical disturbance noise is configured to detect the electrical disturbance noise from a change in temperature data output from the temperature sensor. The electronic balance for detecting electrical disturbance noise according to claim 1. The detection means for detecting electrical disturbance noise is provided with means for storing the limit value of the actual temperature change per unit time and a comparison means. The comparison means compares the change amount of the temperature data with this limit value. 3. The electrical apparatus according to claim 2, wherein when the amount of change in temperature data exceeds a limit value, the change in temperature data is caused by electrical disturbance noise and the presence of electrical disturbance noise is determined. Electronic scale that detects disturbance noise. Sensors that measure different physical quantities such as temperature, humidity, atmospheric pressure, etc. are provided, and means for detecting electrical disturbance noise is the change of at least two types of physical quantity data among the physical quantity data output from these sensors. 2. An electron for detecting electrical disturbance noise according to claim 1, wherein the electronic disturbance noise is determined to be observed when the plurality of physical quantity data show the same change at the same time. Scale. The wiring arranged between the sensor for detecting the physical quantity and the means for displaying and calculating the load data is configured to be used as an antenna for detecting electrical disturbance noise. An electronic balance for detecting electrical disturbance noise according to claim 1.

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