JPH0422825A - Electronic balance - Google Patents

Abstract

PURPOSE:To enable zero point correction to be performed for not only a small range but a large range and to improve measuring accuracy by performing the zero point correction by switching the small range and the large range when a load shows 0g after a power source is applied. CONSTITUTION:A microprocessor 4, when reading in a count value from an A/D converter 3, stores the count value in a RAM 6, and judges a weighing value from the count value in the RAM 6. The zero point in the small range can be decided when the load for a load cell 1 shows 0g. After that, when the load shows 0g at a time, for example, when three minutes elapse after initial processing is completed, a range is automatically switched from the small range to the large range, and the zero point in the large range is decided. After that, the range is automatically returned to the small range, and the zero point correction in the small range is performed. Also, the load is checked even at a time when, for example, nine minutes elapse, and when the load shows 0g, the range is automatically switched from the small range to the large range, then, the zero point correction at the large range is performed. Afterwards, the range is returned to the small range, then, the zero point correction is performed in the small range.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to an electronic scale that can be switched between ranges.

[Prior Art] Some electronic scales that use a load cell as an electronic weight sensor, for example, amplify the output of the load cell with an amplifier, then change the range depending on whether or not it passes through an attenuator. It is known to convert the count value into a digital count value using an analog/digital converter and input it into a weight display device.

Conventionally, zero point correction has been performed only for small ranges and not for large ranges.

[Problem to be solved by the invention] However, in conventional electronic scales that change ranges in this way, the zero point in the small range and the zero point in the large range may change due to changes in environmental conditions such as ambient temperature or drift in the power supply. There is a problem in that the zero points do not necessarily change in the same way, and the deviation of the zero points in both ranges causes errors such as span and instrumental error, making it impossible to perform accurate weight measurements.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electronic scale that can perform zero point correction not only for a small range but also for a large range, and that can improve measurement accuracy.

[Means for solving the problem] Convert the voltage signal from an electronic weight sensor that outputs a voltage signal in response to the load into a digital count value using an analog/digital converter, and create weight data from the count value. In electronic scales that change the count value from an analog/digital converter that corresponds to the load to switch between the small range and the large range, when the load is 0 g after the power is turned on, the small range and the large range are switched. The ranges are alternately switched and zero point correction is performed for each range.

[Function] In an electronic scale with such a configuration, zero point correction is performed not only for the small range but also for the large range when the load is 0 g after the power is turned on. Even if the zero point in the small range and the zero point in the large range do not necessarily change in the same way due to drift of the Be able to do it accurately.

[Embodiment 1] Hereinafter, an embodiment in which the present invention is applied to a load cell type scale will be described with reference to the drawings.

In Fig. 1, 1 is a load cell as an electronic weight sensor that outputs a voltage signal according to the load, 2 is an amplification section that amplifies the load cell output, and 3 is an input device for inputting the voltage signal output from this amplification section 2. Analog/digital (hereinafter abbreviated as A/D) that converts into a digital count value
The converter 4 is a microprocessor which interrupts the count value from the A/D converter 3 at predetermined cycles and processes the captured data.

The amplifying section 2 includes two stages of amplifiers 23 and 2□, and an analog switch 5 is connected between the input terminal and the output terminal of the amplifier 22 at the subsequent stage.

The microprocessor 4 receives the count value from the A/D converter 3, stores the count value in the RAM 6, determines the weighing value from the count value in the RAM 6,
It is checked whether the weighed value is 5 kg or more, which is the weighed value set in advance for switching from the small range to the large range. When the weighed value is 5 kg or more, the switching control circuit 7 closes the analog switch 5 and switches to the large range, and when the weighed value is less than 5 kg, the switching control circuit 7 opens the analog switch 5 and switches to the large range. I'm trying to switch to the microwave.

That is, in a small range, the amplification of the amplifier section 2 is performed by the amplifier 20.
, 2° results in a two-stage amplification, and in a large range, the amplification in the amplifier section 2 is amplified only by the amplifier 2. Therefore, as shown in Figure 2, 5 kg is 1.25,000 counts in the small range, whereas it is 25,000 counts in the large range, and the count value for the load is 115 in the large range compared to the small range. It becomes.

The microprocessor 4 processes the data in the corresponding range based on the count value thus obtained, and creates weight data. This weight data is further rounded for display and displayed on a display 9 via a keyboard/display controller 8. This display roundness is, for example, when in the small range, 1 st - 5 counts = 0.2 g, and in the large range, 1 st - 50 counts = 10 g. Further, a keyboard 1-0 is connected to the keyboard/display controller 8, and key signals from this keyboard 10 are taken in.

Further, the microprocessor 4 is programmed to execute a wide range zero point correction process shown in FIG. 3 after the power is turned on.

That is, in response to the power being turned on, initial processing such as scanning of the display 9 is executed, and when the initial processing is successfully completed, a built-in timer starts measuring time. Next, as ST (step) 1, an arbitrary flag F in the RAM 6 is checked. If the flag F has been reset to 0', then in ST2 it is determined whether the elapsed time from the time of completion of the initial processing as measured by the timer is a preset time. Here, if it is not the set time, as described above, the range is changed according to the load, and the count data is processed, weight data is created, and the weight data is displayed on the display 9. Further, when the load is -0 g, zero point correction is always performed to follow changes in the zero point in a small range.

(Normal Processing) On the other hand, the flag F is reset to "0" in S11, and the time measured by the timer in Sr1 is a set time (for example, 3 minutes, 9 minutes, 39 minutes).

69 minutes, . . .), the flag F is set to "1', and the current load is checked.

If the load is not 0g here, the process returns to normal processing.

Further, if the load is 0 g but the output of the load cell 1 is not stable, the process returns to normal processing.

On the other hand, when the load is 0 g and the output of the load cell 1 is stable, the switching control circuit 7 closes the analog switch 5 and switches from the small range to the large range. Also, the flag F is reset to "0". Next, check the current load again. Is the load here 0g?
Otherwise, the switching control circuit 7 opens the analog switch 5 to switch from the large range to the small range, and then returns to normal processing. Also, if the load is 0 g or the output of the load cell 1 is not stable, the process returns to normal processing after switching from the large range to the small range.

On the other hand, when the load is 0 g and the output of the load cell 1 is stable, the current true value is set in the RAM 6 as the zero point in the large range. Thereafter, the analog switch 5 is closed by the switching control circuit 7 to switch from the small range to the large range, and then normal processing is resumed.

Note that if the flag F is set to "1" in S11, even if the time measured by the timer coincides with the preset time and the flag F is set to "1". Regardless, the current load is checked again because the load is other than O or the output from load cell 1 is unstable and zero point correction processing in a large range is not performed.

Then, if the load is 0g and the output of load cell 1 is stable, switch from the small range to the large range,
Zero point correction in a large range is performed in the same manner as above.

In a load cell scale having such a configuration, when the power is turned on and predetermined initial processing is completed, it is first determined whether the load on the load cell 1 is 0 g and the zero point in the small range. Thereafter, for example, if the load is 0 g after 3 minutes have passed from the completion of the initial processing, the small range is automatically switched to the large range, and the zero point in the large range is determined. Thereafter, the system automatically returns to the small range and zero point correction is performed in the small range.

For example, the load is checked even after 9 minutes have elapsed from the completion of the initial processing, and if it is 0g, the small range is automatically switched to the large range, and the zero point in the large range is corrected. Thereafter, the system automatically returns to the small range and zero point correction is performed in the small range.

After that, for example, 39 minutes from the time the initial processing is completed.

A load check is performed every 30 minutes, such as 69 minutes, and if the load is 0 g at that time, the small range is automatically switched to the large range, and the zero point in the large range is corrected. Also, while the zero point correction in the large range is not performed, the zero point correction in the small range is performed at any time with a load of 0 g.

is being carried out.

Furthermore, if the load is other than 0g after a preset time (for example, 3 minutes, 9 minutes, 239 minutes, 69 minutes, etc.) has elapsed since the completion of the initial process, the zero point determination process in the large range will not be performed. Then, after the load reaches 0g and the load cell output becomes stable, the above-described zero point determination process in the large range is performed.

In addition, if the load changes during the period (approximately 5 seconds) after automatically switching from the small range to the large range until the zero point is determined in the large range, it will immediately return to the small range and resume normal weighing operation. is executed. In this case, the zero point in the large range will be calculated using the previous zero point.

Generally, in electronic scales that can switch ranges, the zero point in the small range and the zero point in the large range may not necessarily change in the same way due to changes in environmental conditions such as ambient temperature or drift in the power supply. . However,
In the load cell scale of this embodiment, zero point correction in the small range is performed whenever the load is 0 g.
It always follows the fluctuation of the zero point. Further, after the power is turned on, zero point correction in the large range is performed every time a preset time elapses after the initial processing is completed. Therefore,
The zero point in the small range and the zero point in the large range are constantly corrected independently, so the zero point in the small range and the zero point in the large range may change due to changes in environmental conditions such as ambient temperature, drift in the power supply, etc. Even if the weight does not necessarily vary in the same way, span and instrumental errors are eliminated, making it possible to accurately measure weight not only within a small range but also within a large range.

It goes without saying that the zero point correction timing in the large range is not limited to the above embodiment. Furthermore, the present invention is not limited to load cell scales, but can be applied to scales using electronic weight sensors other than load cells, such as electrostatic scales. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, the present invention provides an electronic scale that can perform zero point correction not only for small ranges but also for large ranges, and that can improve measurement accuracy. can.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a block diagram of a load cell type scale, Fig. 2 is a characteristic diagram showing the relationship between load and count value in the small range and large range, and Fig. FIG. 3 is a flowchart showing a large range zero point correction process performed by a microprocessor. DESCRIPTION OF SYMBOLS 1... Load cell, 2... Amplification part, 3... Analog/'digital (A/D) converter, 4... Microprocessor, 5... Analog switch, 7... Switching control circuit, 9...Display device. How many diagrams count soft ↑ diagram violet

Claims (1)

[Claims] A voltage signal from an electronic weight sensor that outputs a voltage signal in response to a load is converted into a digital count value using an analog/digital converter, and weight data is created and displayed from the count value. In an electronic scale that switches between the small range and the large range by changing the count value from the analog/digital converter that corresponds to the load, when the load is 0 g after power is turned on, the small range and the large range are switched. An electronic scale characterized by performing zero point correction by switching alternately.