JPH0715403B2 - Battery operated electronic scale - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic scale that uses a battery as a power source,
The present invention relates to a battery-powered electronic scale that incorporates a variable capacitor whose capacity changes according to weight into an oscillation circuit and measures the weight of an object based on the frequency from the oscillation circuit.

<Prior Art> An electronic scale using a battery has an advantage that it can be easily carried and that an object can be weighed in a place without a commercial power source.

A conventional electronic balance using a battery mainly uses a variable capacitance capacitor whose electrostatic capacity changes due to weight from the viewpoint of low power consumption.

FIG. 4 shows a conventional battery-powered electronic scale, in which an indicator (2) and a power switch (3) are provided on the surface of the casing, and a saucer (4) for mounting an object is attached to the opening of the casing. ing. Then, in the casing, a leaf spring (5) for supporting the saucer (4) and a leaf spring (5)
An oscillation circuit (81) incorporating a variable capacitor (6) whose electric capacitance changes according to the deflection of the
A microprocessor (91) for calculating the weight based on the frequency of the output signal from 1) and the power switch (3)
Through the oscillator circuit (81), microprocessor (91),
And a dry battery (10) connected to the display (2) (see FIG. 5).

The variable capacitor (6) has a pair of electrodes (61).
(62), one electrode (61) is attached to the leaf spring (5) through the support (7), and the other electrode (62) is fixed to the bottom surface of the casing (Fig. 1). (See B).

In the electronic balance having the above structure, when the object is placed on the pan (4), the leaf spring (5) bends in direct proportion to the weight of the object, and the upper electrode (61) of the variable capacitor (6). Is displaced downward and the distance between the electrodes (61) and (62) is shortened, so that the capacitance increases. The oscillation frequency of the oscillation circuit (81) decreases as the capacitance increases. Then, the microprocessor (91) counts the oscillation frequency and performs arithmetic processing based on the frequency.
The weight of the object is calculated, and the calculation result is displayed on the display (2).

In the above case, if the power switch (3) is always closed, the oscillation output may decrease due to a decrease in electromotive force due to the exhaustion of the dry battery (10), and a metering error may occur. In order to prevent the dry battery (10) from being consumed as much as possible, the power is not always turned on, but the power is turned on when an object is placed on the pan or immediately before the start of weighing.

<Problems to be Solved by the Invention> However, in the above electronic scale, the oscillation frequency of the oscillation circuit (81) becomes unstable due to a steep current or chattering when the power switch (3) is turned on, so that an error occurs. The metering operation of the microprocessor (91) must be stopped for a certain period of time after the power switch (3) is turned on until the oscillation frequency stabilizes. The microprocessor (91) does not start immediately after the power is turned on until the power is stabilized in order to prevent malfunction, but the time from when the power is turned on until the start is determined by the frequency of the oscillation circuit (81). Short compared to the time to stabilize. Therefore, the measurement error is caused by the instability of the frequency of the oscillation circuit (81) after the startup of the microprocessor.

<Purpose> The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery-powered electronic scale that can stabilize the frequency of an oscillation circuit when a switch is opened and can quickly measure an object. To aim.

<Means for Solving Problems> The battery-powered electronic balance of the present invention for achieving the above object is
At least the oscillation circuit is always connected to the solar cell.

However, the power supply unit may be one in which a solar cell and a secondary battery are connected.

<Operation> In the battery-powered electronic balance of the present invention as described above, at least the oscillation circuit is always connected to the solar cell, and therefore the oscillation circuit is operated by the power source even when the object is not placed on the scale. It has been turned on and is being driven, that is, in a stable state. Then, the object is placed on the scale, and the frequency of the oscillation circuit changes accurately in response to the change in the capacitance of the variable capacitor.

Therefore, since the microprocessor can perform weighing based on the accurate oscillation frequency, the weighing can be started immediately when the object is placed.

Also, when the power supply is a solar cell and a secondary battery connected, by connecting only the oscillation circuit to the solar cell in the state of not measuring, by opening the other circuit, The oscillation circuit can be kept in a standby state, the secondary battery can be charged, and it is not necessary to consider the consumption of the battery.

<Examples> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating examples.

FIG. 1 shows a battery-powered electronic balance as an embodiment of the present invention, in which a solar cell (1), an indicator (2), and a power switch (3) are provided at predetermined positions on the surface of the casing, and the upper part of the casing is provided. A saucer (4) is attached to the opening. And
Inside the casing, a leaf spring (5) whose peripheral edge is fixed to a step inside the casing, a variable capacitor (6) whose electrostatic capacity changes according to the deflection of the leaf spring (5), and a saucer (4 ) And the leaf spring (5) and between the leaf spring (5) and the variable capacitance capacitor (6), and the struts (7) and (7 ') interposed, and the variable capacitance capacitor (6). And a weight measuring device (8) for measuring the weight of the object on the basis of the change in capacitance.

The variable capacitor (6) has a pair of electrodes (61).
(62), one electrode (61) is attached to the leaf spring (5) through the support (7), and the other electrode (62) is fixed to the bottom surface of the casing. Then, as the leaf spring (5) bends, one electrode (61) is displaced,
The capacitance increases as the distance between the electrodes (61) (62) decreases.

The configuration of the weight measuring device (8) will be described with reference to the block diagram of FIG. 2. In the weight measuring device (8), an oscillation in which the variable capacitor (6) is incorporated as a part of an oscillating element is used. The circuit (81), a microprocessor (91) for calculating the weight based on the frequency of the output signal from the oscillation circuit (81) and causing the display (2) to display the weight, and one electrode having the solar cell (1). ) Connected to the ground side, and the other electrode of the dry battery (10) connected to the power switch (3). The oscillation circuit (81) is, for example, as shown in FIG. 3, a multivibrator in which a variable capacitance capacitor (6) for determining an oscillation frequency and a resistor (82) are connected to an amplifier element (83) with very low power consumption. Are using.

In the electronic scale configured as above, the oscillation circuit (81) is the solar cell (1).
It is connected to and is always driven. That is, it is in a standby state. Then, by turning on the power switch (3) and placing the object on the saucer (4), the leaf spring (5) bends in accordance with the weight of the object, and the upper electrode () of the variable capacitor (6) ( The capacitance increases as the distance between the electrodes (61) and (62) becomes shorter due to the displacement of 61) downward. The oscillation frequency of the oscillation circuit (81) decreases as the capacitance increases. The microprocessor (91) counts the oscillation frequency, performs arithmetic processing based on the frequency, calculates the weight of the object, and displays the calculation result on the display (2).

In this case, the oscillation circuit (81) is the solar cell (1).
Since this solar cell (1) is a stable power source whose electric potential is physically determined, it outputs a signal of a constant frequency when no object is placed. That is, since the oscillation circuit (81) is connected to the solar cell (1) having a stable potential to bring it into a stable state, the oscillation circuit (81) is changed according to the change in the capacitance caused by the object placed.
The frequency of the output signal of changes accurately. Therefore, the power switch (3) may be placed just before the object is placed on the saucer (4) as described above or after the object is placed, so that the power switch (3) is always turned on, The weight of the object can be displayed immediately and accurately.

In summary, since the oscillation circuit (81) is always connected to the solar cell (1) which is a power source that does not need to consider the consumption of the battery, the oscillation circuit (81) is always in a stable state,
The oscillation frequency accurately changes according to the change in the capacitance of the variable capacitor (6) due to the object placed on the pan (4). Therefore, when the power switch (3) is turned on, the weight of the object can be displayed immediately and accurately.

Incidentally, the present invention is not limited to the above-mentioned embodiment, for example, the secondary battery is used instead of the dry battery (10),
It is possible to charge the secondary battery to the solar cell (1), use the variable capacity capacitor (6) of the rotary type, and use a coil spring instead of the leaf spring (5). In addition, various design changes can be made without departing from the scope of the invention.

<Effects of the Invention> As described above, according to the battery-powered electronic balance of the present invention, at least the oscillation circuit is connected to the solar battery that is a power source that does not need to consider the life of the battery. It is driven and is in a stable state, and the oscillation frequency accurately changes according to the change in the capacitance of the variable capacitor caused by the object placed on the balance. Therefore, there is a peculiar effect that the weight of the object can be measured immediately and accurately.

[Brief description of drawings]

FIG. 1 is a perspective view and a schematic view of a battery-powered electronic balance as an embodiment of the present invention, FIG. 2 is a block diagram of the embodiment shown in FIG. 1, and FIG. 3 shows details of the oscillator circuit shown in FIG. 4 is a perspective view of a conventional battery-powered electronic scale, and FIG. 5 is a block diagram of the conventional battery-powered electronic scale. (1) …… Solar cell, (2) …… Display unit, (3) …… Power switch, (6) …… Variable capacitor, (81)…
… Oscillator, (91)… Microprocessor, (10)…
… Batteries.

Claims (2)

[Claims] 1. An electronic scale for measuring the weight of an object based on a frequency from an oscillating circuit incorporating a variable-capacitance capacitor whose electrostatic capacity changes according to weight, at least the oscillating circuit being constantly connected to a solar cell. A battery-operated electronic scale characterized by being provided. 2. The battery-powered electronic scale according to claim 1, wherein the power source unit is a solar battery and a secondary battery connected to each other.