JPS60120224A - Voltage-signal arithmetic device - Google Patents

Abstract

PURPOSE:To make it possible to perform reset operation per tare by an analog signal and to implement general purpose applications, by providing an operational amplifier device, which obtains the difference between the voltage at a connecting point of a switch and a capacitor that are connected in series between an input terminal and the ground, and an input voltage. CONSTITUTION:A resistor 7, a reset switch 8, and a capacitor 9 are connected to the output terminal of a first operational amplifier 6, which receives an input voltage Vi. An operational amplifier device 10 is constituted by operational amplifiers 11 and 12 and resistors 13-16. The voltage at the connecting point of the switch 8 and the capacitor 9 is inputted to the amplifier 12 through the amplifier 11. The output voltage of the amplifier 6 is directly inputted to the amplifier 12 through the resistor 7. The switch 8 is turned ON and the capacitor 9 is charged. The specified values of the resistors 13 and 14 are selected and the output voltage V0 of the device 10 is made to be zero. After the switch 8 is turned OFF, the voltage Vi is changed. Then the amount of negative change becomes the voltage V0.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an analog signal calculation device that can be applied to a tare removal device for weighing scales and the like.

2. Description of the Related Art Structures of Conventional Examples and Problems Therein In recent years, digital weight scales with a digital weight display have been increasingly produced in place of pointer-type weight scales for household use. The reason for this is that digital weighing scales have a counter in the weight counting section.
Another reason is that the configuration of the tare removing device is easy because a microcomputer or the like is used.

Fig. 1 shows a conventional tare removal device, in which 1 is a weight sensor that detects weight and converts it to voltage, 2 is an A-D converter that inputs the output of the weight sensor and converts it into a digital signal, and 3 is a microcomputer, which includes an input section 3a for inputting signals from the outside, a storage section 3b for storing the operating program of the microcombiner 3 and temporarily storing data, etc., and outputting signals to the outside. It has an output section 3C, and an arithmetic control section 3d that controls the input section 31L, the storage section 3b, and the output section 3C, and also performs comparison and calculation of data and the like. When a reset signal is input from the reset switch 4, the output signal of the M/D converter 2 is input from the input section 3a, and the input contents are stored in the storage section 3b. When the reset switch 4 is turned off, the output of the A/D converter 2 is inputted from the input section 3a, this input content is compared with the above-mentioned stored content, and the calculation result is outputted from the output section 3C and displayed. This is to display information on the device 6.

The operation of the conventional electronic meter shown in FIG. 1 constructed as described above will be described below.

The weight sensor 1 outputs a voltage signal proportional to the load of the object to be measured, and the voltage increases as the load increases. The A-D converter 2 outputs a digital signal corresponding to the output voltage of the weight sensor 1. The microcomputer 3 detects at the input section 3a that the reset switch 4 is turned on, and thereby inputs the digital signal of the error converter 2 from the input section 31L and temporarily stores it in the storage section 3b via the arithmetic control section 3d. to be memorized. Here, if the load when the reset switch 4 is turned on is Wl, data w'IM corresponding to Wl will be stored in the storage section 3b. Next, when the switch 4 is turned off (or while it is turned off), the microcomputer 3
A signal corresponding to the load of the weight sensor 1 is output from the A/D converter 2 at regular intervals through the input section 3a, and data W2M corresponding to the load W2 is inputted through the input section 3a. At this time, if there is no change in the load since the time when the reset switch 4 was turned on, the value is W1M2W2M, and if there is a change in the load, the value is W1M#W2M. Arithmetic control unit 3
d compares the data W2M input at a certain period with the data WIM stored in the storage section 3b, and calculates W2M-
The value of WlM is outputted via the output section 3C.

In response to this signal, the display device 6 displays the weight determined by the value of W2M-WlM.

That is, when the load is Wl, the reset switch 4
When turned on and off, the load of Wl is input and stored, and thereafter the load of W2-Wl is displayed according to the load of W2. After turning off the reset switch 4, if the load does not change, the display will be 0 at W2-Wl, and when the object to be measured is placed on the weight measuring section, the weight corresponding to the second load will be displayed, and the reset switch will be turned off. By turning on the reset switch 4, the tare can be reset, and after turning off the reset switch 4, the weight of the object to be measured placed on the weight measuring section can be known. In this way, a weighing scale with a tare reset function is constructed.

However, the conventional tare reset device configured as described above has a narrow range of application because it is performed by calculations by a gage counter such as a microcomputer, and can only be applied to digital weighing scales. Also, the second
The figure shows the relationship between load and output in the conventional example shown in FIG. The horizontal axis represents the load, and the vertical axis represents the output of the A/D converter.

In FIG. 2, the resolution per 1 bit of the A/D converter 2 is 1 g, and the output from the A/D converter 2 is rounded down to the nearest whole number. The operation of the embodiment shown in FIG. 1 will be explained based on FIG. 2. Wl in FIG. 2 indicates 2.1 g,
Assuming that w2 indicates 4.9fl, ws indicates 2.9g, and W4 indicates 4.1g, first, when the reset switch 4 is turned on when the load is W1, the storage section 3b
2g is stored inside. Next, when a load of W2 is applied, the input to the microcomputer 3 will be 4g, and the output section will output an output of 4f-29=2da, and the display device 5 will display 2g. . However, the actual load is... 2-Vl 1 =4.99-2.1 g=2
．． At 8f, an error of -0.8f is displayed. Similarly, W
When a load of 3 is applied, the reset operation is performed and a load of w4 is applied, the display is af-29=29, and 2g
is displayed, but the actual load is 4.1 p −2,91=
1.29, and an error of +Q, 8 f will be displayed. That is, in the apparatus shown in FIG. 1, the actual display has a maximum error of ±1 g.

As described above, in the conventional device as shown in FIG. 1, the application is limited to digital weighing scales, which limits the scope of use and still has the problem of large errors during calculation.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems.The present invention has a simple configuration and is capable of performing a tare reset calculation using an analog signal, instead of a conventional tare reset calculation using a digital signal. The purpose is to provide a computing device.

Composition of the Invention The present invention provides a series circuit of a switch and a capacitor connected between a voltage signal input terminal and ground, and a system that calculates the difference between the voltage at the connection point of the switch and the capacitor and the voltage input from the input terminal. This is a voltage signal calculation device equipped with an arithmetic amplification device that outputs the data, and allows calculations to be performed using analog signals instead of standard value setting calculations such as tare reset, which were conventionally handled using digital signals. As a result, it is versatile and can also improve accuracy.

DESCRIPTION OF THE EMBODIMENT FIG. 3 is a specific circuit diagram in an embodiment of the present invention. In the figure, 6 is a first operational amplifier configured as a voltage follower to input the input voltage and increase current capacity, and 7 is a relatively low resistance value for current limiting connected to the output terminal of operational amplifier 6. 9 is a capacitor having one end connected to the switch 8 and the other end grounded, the capacitor having a capacitance of about 100 cm and a low leakage current.
10 is an operational amplification device, and an operational amplifier 6 is connected to one of the input terminals.
The output voltage of the capacitor 9 and the switch 8 is inputted through the resistor 7, and the voltage at the connection point between the capacitor 9 and the switch 8 is inputted from the other side, and both input values are calculated and the results are output. 11 is an operational amplifier of the arithmetic amplification device 10;

The input terminal 7 is configured as a voltage follower that inputs the voltage of the capacitor 9, amplifies the current, and outputs the current. l: Constructed with high impedance. 12 is an operational amplifier that constitutes the differential amplifier 1 circuit, and the output of operational amplifier 6 and operational amplifier 1
It is configured to input the outputs of 1 and perform differential amplification. 13 to 16 are resistors that constitute a differential amplification circuit together with the operational amplifier 12.

The operation of the voltage calculation device of this embodiment configured as described above will be described below.

A voltage proportional to the weight is input to the input voltage Vi. If the current capacity of this input signal is sufficient, there will be no problem, but in order to prevent operational problems even if the capacity is small, an operational amplifier 6 is provided at the input terminal section. A voltage equal to Vi is output. Since the resistor 7 has a low resistance value of about several ohms, the voltage drop due to the resistor 7 is almost zero and can be ignored if the current flowing through the resistor 7 is small. That is,
The operational amplifier 6 and the resistor 7 are not necessary if a device capable of drawing a sufficient current is connected to the input section. When the switch 8 is turned on, the capacitor 9 is charged by the output voltage of the operational amplifier 6 via the resistor 7 and the switch 8. At this time, the time constant of the circuit is not large, so
Capacitor 9 is charged instantaneously, and the voltage of capacitor 9 becomes equal to the output voltage of operational amplifier 6. The voltage of the operational amplifier 11 and the capacitor 9 is input, and a voltage equal to this voltage is output. Op-amp 12 and resistors 13-1
6 constitutes a differential amplification circuit, and resistors 13 and 16 or resistors 14 and 16 are each configured to have the same resistance value, and the voltage on the input side of resistor 13 and resistor 16 connected to the input terminal of operational amplifier 12 is Each Vi2. If Vi+, the output voltage of the operational amplifier 12 is determined by the ratio of the resistance values of the resistor 13 and the resistor 14, and the resistance value of each is 113. R14
Then, the output voltage of the operational amplifier 12 is vQ=R1a
(v4.-Vi2)/R1s. That is, since the voltage of the capacitor 9 is equal to Vi, the arithmetic amplification device 10
is configured to amplify the difference between the voltage of the capacitor 9 and the output voltage of the operational amplifier 6 by a constant ratio. Here, if R13=114, Vo=(Vll-Vi
2) becomes.

Now, if the switch 8 is on, the voltage of the capacitor 9 is equal to Vi, and vO becomes 0 with vi+=V<2>. Furthermore, even after the switch 8 is turned off, the voltage of the capacitor 9 remains unchanged because the impedance of the input terminal of the operational amplifier 110 is high, and the voltage remains the same as when the switch 8 was turned on. are doing. Therefore, both Vi+ and Vi2 do not change,
The output remains O. Next, if the voltage of Vl changes by ΔV, the output voltage of the operational amplifier 6 is vi+ΔV
In addition, the voltage of the capacitor 9 remains at Vi, and the output vO becomes vO-vi-(vi + Δv) = -ΔV, and after turning off the switch 8, the voltage corresponding to the change in input Vi becomes negative. It will now be output as a sign. By converting the sign of the output voltage VO, the output voltage corresponds to the change in the input voltage after the switch 8 is turned off.

That is, according to the embodiment shown in FIG. 3, there is provided a voltage signal calculation device that can easily tare the analog signal by resetting the analog voltage input with the switch 8 and outputting the change after the switch 8 is turned off. It consists of

It is the cause.

In the figure, 17 is a variable resistor, which is provided so that the slider 171L slides depending on the load W. Although not shown in the figure,
The load sum 2o is proportional to the load W, and the slider 17& moves because a resistance force is applied to the load W by a spring or the like. Therefore, the output Vi outputs a voltage proportional to the load WK. Further, 18 is a voltage signal calculation device shown in FIG. 3, 19 is a display means having a structure similar to a voltmeter connected to the output terminal of the voltage signal calculation device 18, and a scale of the load is recorded on the scale plate. The pointer rotates by an angle proportional to the voltage applied to the coil.

The operation of the weighing scale constructed as described above will be explained. The variable resistor 17 outputs a voltage proportional to the load W. Further, the output voltage To of the voltage signal calculation device 18 is a voltage T correlated to the input voltage v4.

The display means 19 performs an analog display proportional to the negative voltage vO. Now, when the load WI is applied, the output voltage of the variable resistor 17 is Vi, and at this time,
When the switch 8 shown in FIG. 3 (not shown) is turned on, the output vO of the voltage signal calculation device 17 becomes Ov, and the display means 19 displays 0. Next, after turning off this switch 8, when the load W1 is changed by .DELTA.W, the output voltage of the variable resistor 17 becomes Vi, +.DELTA.V, and the output of the voltage signal calculation device 17 becomes -.DELTA.V. Here, the display means 19 displays ΔW in order to display the negative voltage ΔVK proportional to the input negative voltage ΔVK.

Therefore, according to the configuration shown in FIG. 4, a weighing scale equipped with a tare reset function can be easily constructed using the voltage signal calculation device of the present invention. Moreover, in FIG. 4, an analog display system is used, which is completely new and completely new.

In the embodiment shown in FIG. 4, the display means 19 is of an analog type, but it is also possible to replace it with a MU/D converter and a 7-segment display means.
The voltage input to the D/D converter is always proportional to ΔW when the switch 8 is turned on and when the load changes after it is turned off, so the voltage signal is a voltage signal with almost no error in tl. is input, and the only error in the device is an approximation error caused by converting an analog signal into a digital signal, and a highly accurate weighing device is constructed. For example, compared to the conventional example shown in FIGS. 1 and 2, the error range in the conventional example is twice the minimum digital display interval 1f, that is, an error of ±1 g with respect to the display. In the case of this embodiment, the value is +1g to -Of with respect to the display.

Effects of the Invention The present invention has a series connection of a switch and a capacitor connected between a voltage input terminal and ground, one end of the input terminal is connected to the connection point of the switch and the capacitor, and the other end is connected to the voltage input terminal. and a device for amplifying the voltage input to both input terminals.
It is possible to realize a voltage signal calculation device that can perform air removal calculation of an analog signal with easy operation using a simple circuit configuration. Furthermore, since calculations are performed using analog signals, it has the advantage of reducing conversion approximation errors even when the output is converted into digital data, and is expected to have a wide range of applications. It is.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a weighing scale equipped with a conventional tare removal device.
Fig. 2 is a correlation diagram between the weight of the container and the display to explain the operation of the conventional example, Fig. 3 is a specific circuit diagram of the voltage signal calculation device according to an embodiment of the present invention, and Fig. 4 is the voltage signal calculation device. FIG. 2 is a schematic configuration diagram in which the method is applied to a weighing device. 8...Switch, 9...Capacitor,
10... Operator device, 11... Operational amplifier, 12... Operational amplifier, 13-16...
····resistance. Figure 1 Figure 2 FI declaration 3 Figure n

Claims (1)

[Claims] a series circuit of a switch and a capacitor connected between an input terminal and ground; and an operational amplification device that outputs a difference between a voltage at a connection point of the switch and the capacitor and a voltage input to the input terminal. A voltage signal calculation device consisting of.