JPS638408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a weighing machine that employs a load transducer configured to output a digital signal corresponding to a load value with a resolution of a constant load interval throughout the entire weighing section.

One way to improve the stability of the zero point in the weighing machine is to widen the pull-in range of automatic zero tracking by increasing the minimum scale. However, when the minimum scale of a conventional weighing machine is increased, the accuracy of weight value display decreases, and it is difficult to satisfy both the weight value display accuracy and zero point stability.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an electronic weighing machine that can improve the stability of the zero point without sacrificing the accuracy of weighed value display.

An embodiment of the present invention will be described below based on the drawings.

1 is a load cell that outputs an analog voltage V _A corresponding to a load value, and 2 is an analog-to-digital converter that samples the analog voltage V _A via an amplifier 3 at predetermined intervals and generates a digital signal corresponding to the sampled value. For example, the weighing value data D is output with a resolution of 1 g of the minimum scale throughout the entire weighing section. Reference numeral 4 denotes an identification circuit that determines the weighing value data D and set values (d ₁ ) to (d ₃ ) corresponding to a predetermined weight value in the weighing section.
It is determined in which of the weighing sections divided by the set value the weighing value data D is included. For the purpose of explanation, the weighing machine has a total weighing range of 0 to 10 [Kg] as shown in Figure 2a, and the setting values (d ₁ ) The first weighing interval of 0 to 40 [g] including the zero point by (d ₂ ) (d ₃ ), and 40
[g] to 2 [Kg] second weighing interval, and 2 [Kg]
The third weighing interval of ~4 [Kg] and the third weighing interval of ~4 [Kg] ~10
[Kg] It is identified in which interval the weight value data D is included in the fourth weighing interval, and the output lines l ₁ to l ₄ are selectively set to logic level “H” according to the identification result. ” shall be reversed. Reference numeral 5 denotes a minimum scale switching circuit which processes the weighing value data D using the output lines _{l1 to l4} of the identification circuit ₄ as control signals. The least digit (LSB) of weighted value data D is “6”
~ “9” becomes “5” and the least digit (LSB) is “0”
~ “4” outputs data D by aligning it with “0”, and when output line _l2 is at logic level “H”, all digits of weighing value data D are passed through as is, and output line _l3 is at logic level In the "H" state, the data D is output by truncating the odd number of the least significant digit (LSB). 6 is a display device which digitally displays the digital signal D output from the minimum scale switching circuit 5 as a weight value. 7 is an automatic zero tracking device, in which the minimum scale of the first weighing section including the zero point is 5g, so the weighing value is 0± as shown in Figure 2b.
For example, the load cell 1 and the analog
A load converting section consisting of a digital converter 2 is automatically corrected.

Next, the operation shown in FIG. 1 will be explained based on a specific circuit example of the minimum scale switching circuit 5 shown in FIG. In this weighing machine, when the weighed value is included in the second, third or fourth weighing interval, the minimum scale is 1, respectively.
g, 2g, and 5g, and in the first weighing section including the zero point, the minimum scale is 5g, which is larger than the minimum scale of 1g in the adjacent second weighing section. , the minimum scale is 5
Even though the pull-in range of the automatic zero tracking is widened by setting the weight to 100 g, the accuracy of displaying the weight value in the second weighing section is not impaired.

The output signal of the load converter, which operates with a resolution of 1 g minimum scale throughout the entire weighing section, is processed as follows.

When the weight value data D is larger than the set value (d ₁ ) and smaller than the set value (d ₂ ), the output line l ₂ of the discrimination circuit 4 is selected, and the gates G ₁₈ , G ₁₄ , G ₁₂ ,
_G11 is turned on and the minimum scale switching circuit 5 has no effect on the weight value data D, so the display device 6
From this, a weight value display with a minimum scale of 1 g can be obtained.

When the weighing value data D is smaller than the set value (d ₁ ) or larger than the set value (d ₃ ), the output lines l ₁ and l ₄ of the identification circuit 4 are at logic level “H”.
In both cases, the gates G ₃₈ , G ₃₄ ,
G ₃₂ and G ₃₁ are turned on. Gate G ₃₈ , G ₃₄ ,
When G ₃₂ and G ₃₁ are turned on, "4" is added to the least significant digit (LSB) by the adder 8, and only when carry E occurs, the least digit is "5".
If the carry E does not occur, the minimum digit is fixed to "0" and output. Therefore, the automatic zero tracking device 7 operates only when the output line _l1 of the identification circuit 4 is inverted to logic level "H", and continuously records the weight value data for a predetermined period of time.
When D ₀ is below the minimum scale of 5 g, it acts on the load converter etc. to change the shifted point to the zero point.

In the above embodiment, the total weighing interval is divided into four intervals, but the total weighing interval is divided into at least two, the first interval including the zero point and the second interval containing the zero point, and the first interval The same applies if the minimum scale of is larger than that of the second section.

As explained above, according to the present invention, in a weighing machine equipped with an automatic zero tracking device, the output signal of the load converter section that outputs a digital signal according to the load value with a resolution of a constant load interval throughout the entire weighing section is In a first weighing section including a zero point and a second weighing section adjacent to the first weighing section, in response to a division signal corresponding to a weighing section divided into a plurality of sections,
Equipped with a minimum scale switching means that processes the minimum scale of the first weighing section to be larger than the minimum scale of the second weighing section, ensuring zero point stability without sacrificing weigh value display accuracy. This improves the reliability and weighing accuracy of the weighing machine.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a configuration diagram of a weighing machine equipped with an automatic zero tracking function.
Figure 2 a and b are explanatory diagrams of the weighing interval and the minimum scale;
FIG. 3 is a specific configuration diagram of the minimum scale switching circuit. 1...Load cell, 2...Analog-digital converter, 4...Identification circuit, 5...Minimum scale switching circuit, 7...Automatic zero tracking device.

Claims (1)

[Claims] 1. If the weighing value data remains below the minimum scale for a specified period of time, the weighing machine must be equipped with an automatic zero tracking device that acts on the load converter, etc. to change the deviation to the zero point. a load conversion section that outputs a digital signal according to the load value with a resolution of a constant load interval throughout the entire weighing section; a first weighing section including the zero point; and a second weighing section adjacent to the first weighing section. and minimum scale switching means for processing the output signal of the load converter so that the minimum scale of the first weighing section is larger than the minimum scale of the second weighing section. Heavy equipment.