JPH0275913A - Load cell type weighting instrument - Google Patents

Abstract

PURPOSE:To always make a correct display in a selected range by switching the range of the title weighing instrument by switching the using stage number of an amplifier. CONSTITUTION:When a load is applied to a load cell 1, digital data are fetched into a microprocessor 4 from an A/D converter 3. When the load is <5kg, an analog switch 5 is closed by means of a switch control circuit 7 and an amplifying section 2 is set to a small-range operation that is carried out by two-stage amplification by means of two amplifiers 21 and 22. In this state, the stabilized condition of measuring values is judged by <=+ or -0.2g. When another load is applied to the load cell 1 and the data fetched from the converter 3 exceeds 5kg, the microprocessor 4 opens the switch 5 by controlling the circuit 7 and a large-range operation is set. In the initial stage after the range is switched, the microprocessor 4 abandons 1st - 5th data from the converter 3 and fetches the data of the converter 3 from a 6th data as effective data. Thus correct data are fetched under the large-range condition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a load cell type % scale that can switch ranges.
As seen in Publication No. 54618, after the output of the load cell is amplified by an amplifier, range switching is performed depending on whether or not it passes through an attenuator, and the output is then converted into analog/
It is known that weight display data is obtained by converting it into digital data using a digital converter.

[Problems to be Solved by the Invention] However, in the case where range switching is performed using an attenuator as described above, the level of the output of the amplifier is lowered by that amount, resulting in a problem of decreased sensitivity.

For this reason, it is conceivable to provide multiple stages of amplifiers without using attenuators, and to switch the range by switching the number of stages of amplifiers used.

However, when changing the range by changing the number of amplifier stages used in this way, even if the range is changed due to a delay in circuit operation, the correct operation in the switched range will not occur immediately, and it will take a long time before the correct operation is performed. takes some time. For example, as shown in Figure 6, if a switch is made from the small range to the large range when the count obtained by analog/digital conversion exceeds a certain value, then the count number is changed to the large range. It takes time to obtain the correct value, and the data sampled several times immediately after changing the range will be incorrect.

That is, if display data is created and displayed by taking in this erroneous data as is, there is a problem that the display ff1ffi becomes a considerably large weight value immediately after switching to the large range, as shown in FIG.

SUMMARY OF THE INVENTION Therefore, the present invention aims to provide a load cell scale that can switch ranges by changing the number of stages of amplifiers used, without causing a decrease in sensitivity, and that can always display correctly in the selected range. It is.

Furthermore, when changing the range, the weight per stitch value displayed in the small range is usually smaller than that in the large range. For example, in a small weighing range of 0 to 5υ, the first one is 5 counts and 0.29, and in a large weighing range of 5 to 30, it is 1
The eyes will read log at 50 counts.

Furthermore, when displaying weight on a display, the stability of the data is usually determined, and display data is created and displayed on the display. The stability judgment at this time is determined based on the displayed weight value per stitch. In other words, the first eye is 0.29
In the small range of , the stability condition is when the data fluctuation is less than ±0.2 g, and in the large range where 1st is 109, the stability condition is when the data fluctuation is less than ±109. There is. When the range is changed in this way, the conditions for determining stability also change.

However, if the weight values at the range switching point and the stability condition switching point are set to be exactly the same, for example around 5.0, even if the weight value fluctuates around 5.0 υ, it will stabilize once the range reaches the large range. Since the condition is judged to be within a range of less than ±109, it is judged to be stable, and as a result, a problem arises in which it is impossible to perform measurement with accuracy in a small range in the vicinity of 5 points.

Therefore, the invention described in claim (2) makes the ff1m value at the switching point for stability judgment slightly larger than the weight value at the range switching point, and in the vicinity of the range switching point, the display weight is always determined based on the stability condition judgment on the small range side. The purpose is to provide a load cell scale that can create data.

[Means for Solving the Problem] The invention of claim (1) includes a load cell that outputs a voltage signal in response to a load, an amplifying section that includes a plurality of stages of amplifiers and that amplifies the output of the load cell, and this amplifying section. An analog/digital converter that converts the voltage signal from the analog/digital converter into digital data, a weight data creation means that takes in the digital data from the analog/digital converter and creates weight data for display, and a weight data creation means that takes in the digital data and creates weight data for display. The number of stages of amplifiers used in the amplifier section is switched depending on whether the weight value of the digital data exceeds a preset weight value, and when the weight value of the digital data is less than or equal to the set weight value, the number of stages displayed on the weight data creation means is changed. Create data for a small range where the weight value per stitch is small, and when the weight value of the digital data exceeds the set weight value, the weight data creation means creates data for a large range where the weight value per stitch is large. A range switching control means for performing the processing, and a temporary prohibition control means for temporarily prohibiting the weight data creation means from receiving digital data from the analog/digital converter when the range switching control is performed by the range switching control means. and f
A display device is provided to display weight data for display from the f1ffi data creation means.

The invention of claim (2) also provides a load cell that outputs a voltage signal in response to a load, an amplifying section that includes a plurality of stages of amplifiers and that amplifies the output of the load cell, and converts the voltage signal from the amplifying section into digital data. The analog/digital converter to be converted and the digital data from this analog/digital converter are imported, and the stability of the imported data is determined based on the stability conditions determined based on the weight value per stitch to be displayed, and the weight data for display is determined. and a weight data creation means for creating the digital data, and depending on whether the weight value of the digital data taken in by the weight data creation means exceeds a preset weight value, the number of stages of the amplifier used in the amplification section is cut off, and the digital data is When the weight value of the digital data is less than the set weight value, the weight data creation means is made to perform data creation processing for a small range in which the displayed weight value per stitch is small, and the weight value of the digital data exceeds the set weight value. A range switching control means for causing the weight data creation means to perform data creation processing for a large range in which the displayed weight value per eye is large; Temporary prohibition control means for temporarily prohibiting the acquisition of digital data from the analog/digital converter, and If! A display is provided to display weight data for display from the data generating means, and a stable switching weight point determined by the weight data generating means is set to be slightly larger than the range switching weight point of the range switching control means.

[Function] In the invention of claim (1), the amplifier used in the amplifier section is configured to operate in a small range when the weight value of the digital data taken in from the analog/digital converter to the weight data creation means is less than the set weight value. The number of stages is set. Further, the number of stages of amplifiers used in the amplification section is set so that a wide range operation is performed when the weight value of the digital data exceeds a set weight value. In this way, the small range and large range are automatically switched depending on the load.

When the range is changed, the weight data creation means is temporarily prohibited from importing digital data from the analog/digital converter, and then analog/digital conversion is performed at the timing when the correct digital data for the changed range is obtained. The acquisition of digital data from the device is resumed, and display ff1fl data is created.

In addition, in the invention of claim (2), even if the measured value due to the load is near the range switching point and the operation is in the large range, the stability judgment for display is based on the accuracy in the small range operation. This is done with a high level of stability judgment.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a load cell that outputs a voltage signal according to the load, 2 is an amplifier that amplifies this load cell output, 3 is inputted with the voltage signal output from this amplifier 2,
Analog/digital to convert to digital data (hereinafter referred to as
It is called A/D. ) Converter 4 is a microprocessor that receives digital data from the A/D converter 3 at predetermined cycles and processes the data.

The amplifying section 2 includes a two-stage amplifier 2. ．． 22, and an analog switch 5 is connected between the input terminal and output terminal of the amplifier 22 at the subsequent stage.

The microprocessor 4 performs the input processing shown in FIG. 2, takes in digital data from the A/D converter 3, and stores the digital data in the RAM 6. Then, the captured digital data is rounded up as weight data, and it is checked whether the weight data is equal to or greater than 5K9, which is a weighing value set in advance for range switching.

Weight data is 5! If it is determined that the range is j or more, it is then checked whether or not it operated in a large range last time.

If the previous operation was a large range operation, a check is made to see if the digital data has been read and discarded five times. and 5
If not, discard the digital data read this time. Further, if the data has already been read and discarded five times, the digital data read this time is made valid.

Also, if the previous operation was in the large range at 5K9 or higher, switching to the large range is performed.

Furthermore, if the weight data is determined to be less than 5K9, it is then checked whether or not it was operated in the small range last time. If the previous operation was a small range operation, a check is made to see if the digital data has been read and discarded five times. If you have not done this five times, discard the digital data read this time. Further, if the data has already been read and discarded five times, the digital data read this time is made valid.

Also, if the weight is less than 5 kg and the previous operation was in the small range, switching to the small range is performed.

Switching between the large range and the small range in this process is performed by controlling a switching control circuit 7, which opens and closes the analog switch 5.

That is, when the range is small, the analog switch 5 is opened, and when the range is large, the analog switch 5 is closed.

Further, after the microprocessor 4 takes in digital data through input processing, it subsequently performs the flicker processing shown in FIG. 3. In this process, if the captured data is captured in a wide range operation, the flicker processing is performed after multiplying the captured data by 5. If the range is small, flicker processing is performed as is.

This flicker processing prevents flickering by, for example, sampling several pieces of digital data and comparing the sampled digital data, and not changing the display weight data when there is not much difference in variation.

The reason why large range digital data is multiplied by five in this flickering process is as follows. In other words, as shown in Figure 5, the slope of the count number (digital data) with respect to the weight value in the small range is set to 5 times the slope of the count number (digital data) with respect to the weight value in the large range. There is.

When the range is small, it is amplified in two stages by amplifiers 21 and 22, but when it is a large range, it is amplified only by the amplifier 21, and the amplification degree for the small range is different from the amplification degree for the large range. This is because it is set to 5 times.

In addition, the microcomputer 4 performs a small range operation when the value is less than 5 υ, and a large range operation when it is 5υ or more. It is set to 109 at 50 counts. In the small range, the weight value is determined to be stable when the fluctuation is within ±1 degree, i.e., within ±0.2 g, and in the large range, the weight value is determined to be stable when the fluctuation is within ±1 degree, i.e., within ±10 g. I'm trying to make it happen. However, if the range switching point is simply used as the switching point for determining the stability condition, as shown in Figure 4, when the weight value is at three points slightly smaller than the range switching point, small range operation will occur and the stability condition will be ±0. , 2g, but when the weight value is at point b, which is slightly larger than the range switching point, a wide range operation occurs and the stability condition is determined as ±10g. For this reason, the weight value is unstable near point b, and although it is originally not desired to stabilize it, because of the wide range operation, stability conditions are established and a stability determination is made. For this reason, the switching point for determining the stability condition is set at a point that is slightly larger in weight value than the range switching point, for example, 5.1 fat.

Then, the microprocessor 4 rounds the captured digital data into weight data in Durham units,
Furthermore, display flit data is created by converting it into units of weight per eye according to each range, and the display weight data is displayed on a display 9 via a keyboard/display controller 8. . Further, a keyboard 10 is connected to the keyboard/display controller 8, and key signals from the keyboard 10 are received.

In this embodiment having such a configuration, when a load is applied to the load cell 1, digital data is taken into the microprocessor 4 from the A/D converter 3.

At this time, if the load is less than 5 K9, the analog switch 5 is closed by the switching control circuit 7, and the amplifier section 2
is two amplifiers 2. ．． 22 is in a state where two-stage amplification is performed. In other words, it operates in a small range. However, in this state, the stability condition for the weighed value is determined by ±0.2 g or less.

Next, when another load is applied to the load cell 1 and the digital data taken in from the A/D converter 3 exceeds 5, the microprocessor 4 controls the switching control circuit 7 to open the analog switch 5. . In other words, it becomes a wide range operation. Therefore, the amplifying section 2 only amplifies the amplifier 21.

At the beginning of this range switching, even if the microcomputer 4 takes in digital data from the A/D converter 3, it discards it up to five times. From the 6th time onwards, it will be imported as valid digital data. This control for reading and discarding the captured data can be realized by using a timer and discarding the data until the timer times up, since the data is captured at fixed time intervals by interrupts.

In this way, by validating the digital data captured from the sixth time onwards, it becomes possible to capture a wide range of originally correct digital data. In this wide range operation, the stability of the measured value is judged to be within ±10 g. However, even when operating in a large range, stability is determined to be in a small range until the measured value reaches 5.1 fat or higher.

In this state, if the load on load cell 1 is removed, A
Since the digital data taken in from the /D converter 3 falls below 5, the microprocessor 4 controls the switching control circuit 7 to close the analog switch 5. In other words, it becomes a small range.

At the beginning of this range switching, even if the microcomputer 4 takes in digital data from the A/D converter 3, it discards it up to five times. From the 6th time onwards, it will be imported as valid digital data.

In this way, when a load is applied to the load cell 1 and the measured value at that time becomes 5 fat or more, the small range is automatically switched to the large range, but at the beginning of range switching, the A/D
The digital data taken in from the converter 3 is discarded up to five times, so when the digital data from the A/D converter 3 is taken in as valid, the digital data is correct data within a wide range. Therefore, the displayed weight changes smoothly even after passing the range switching point.

Also, while the range switching point is 5 kg, the stability judgment switching point is slightly larger at 5.1 to 9, so when the weighing value is near the range switching point, the data will be ±0.2
Since stability is not determined unless the value is within g, for example, stability is not determined when the data fluctuates within ±1 to 2 g.

Furthermore, the sensitivity in the small range is set to 5 times the sensitivity in the large range, but in flicker processing, the captured data is 5 times as large in the large range, so the sensitivity is the same for both the small and large ranges. Can handle flickering.

[Effects of the Invention] As detailed above, according to the present invention, range switching can be performed by changing the number of amplifier stages used, thereby making it possible to switch ranges without causing a decrease in sensitivity. It is possible to provide a load cell type scale that can display information.

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention.
The figure is a block diagram, Figure 2 is a flowchart showing data input processing by the microprocessor, Figure 3 is a flowchart showing flicker processing by the microprocessor, and Figure 4 is a diagram explaining the relationship between range switching and stability judgment. , Figure 5 is a graph showing the change in count number with respect to the weight of the small range and large range, Figure 6 is a graph showing the change in count number when the amplification stage of the amplifier section is switched by range switching, and Figure 7 is a graph showing the change in count number with respect to the weight of the small range and large range. It is a graph showing a change in displayed weight when the amplification stage of the amplification section is switched by switching. 1... Load cell, 2... Amplifying section, 2. ．． 22...
- Amplifier, 3... Analog/digital (A/D) converter, 4... Microprocessor, 5... Analog switch, 6... RAM, 7... Switching control circuit, 9.
··display. Applicant's agent Patent attorney Takehiko Suzue 3rd factor Shipping fee -1

Claims (2)

[Claims] (1) A load cell that outputs a voltage signal in response to a load, an amplifier section that includes multiple stages of amplifiers that amplifies the output of the load cell, and an analog/digital converter that converts the voltage signal from this amplifier section into digital data. a weight data creation means for taking in digital data from the analog/digital converter and creating weight data for display; The number of amplifier stages used in the amplifying section is changed depending on whether the weight value exceeds the set weight value, and when the weight value of the digital data is less than or equal to the set weight value, data creation processing is performed for a small range in which the weight value per eye displayed on the weight data creation means is small. and when the weight value of the digital data exceeds a set weight value, the range switching control means causes the weight data creation means to perform data creation processing for a large range in which the displayed weight value per stitch is large; Temporary prohibition control means for temporarily prohibiting the weight data creation means from receiving digital data from the analog/digital converter when range switching control is performed by the range changeover control means; and display use from the weight data creation means. A load cell scale characterized by being equipped with a display that displays weight data. (2) A load cell that outputs a voltage signal in response to a load, an amplifier section that includes multiple stages of amplifiers that amplifies the output of the load cell, and an analog/digital conversion that converts the voltage signal from this amplifier section into digital data. Weight data creation process that imports digital data from the device and this analog/digital converter, determines the stability of the imported data under stability conditions determined based on the displayed weight value per eye, and creates weight data for display. and the number of amplifier stages used in the amplification section is switched depending on whether the weight value of the digital data taken in by the weight data creation means exceeds a preset weight value, and the weight value of the digital data is changed to the set weight value. In the following cases, the weight data creation means is caused to perform data creation processing for a small range in which the displayed weight value per stitch is small, and when the weight value of the digital data exceeds the set weight value, the weight data creation means is displayed. a range switching control means for performing a data creation process for a large range in which the weight value per eye is large; and a display device for displaying weight data for display from the weight data creation means;
A load cell type scale, characterized in that a stable switching weight point determined by the weight data creation means is set slightly larger than a range switching weight point of the range switching control means.