JPS62134523A - Balance - Google Patents

Abstract

PURPOSE:To attain miniaturization and the enhancement of balance accuracy and to enable digital display, by providing a pressure detector receiving pressure almost proportional to the wt. of the article to be measured held to a holding part by a lever piece tilting by the wt. of said article, an operation part and a display part. CONSTITUTION:When a stationary body 4 is horizontally maintained prior to a measurement, a movable body 3 falls under its own wt. along with a holding part 3 to push up a diaphragm 8 and, therefore, an internal fluid is pressurized and resistors R1-R4 change. When a switch 13 is turned ON in this state, an operation part 10 can bring the display of a display part 11 to zero and the temp. compensation of a pressure detector 9 can be omitted and not only the own wt. of the movable body 3 but also the error thereof can be absorbed. By allowing the holding part 2 to hold an article to be measured, increased pressure is converted to an electric signal by the pressure detector 9 and the increment thereof is operated by the operation part 10 and the wt. of the article to be measured is digitally displayed on a display part 11 through an AD converter 6. A power source circuit 47 can automatically turn a power source OFF after a definite time was elapsed and the consumption of a battery 12 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a scale that digitally displays the weight of an object to be measured using a pressure detector.

[Background technology]

For example, as a scale for measuring the weight of objects to be measured such as cooking ingredients and mail, spring scales are often used that display analog extension of a coil spring due to load by rotating a pointer using a rank and a pinion. However, such a spring scale is
Large mechanical displacements such as the extension of coil springs due to loads,
Since analog display uses mechanical mechanisms such as racks and pinions, there are limits to miniaturization, poor accuracy, and relatively large weight. It was difficult to measure well. Analog display using a pointer also has the disadvantage that reading errors are likely to occur.

Therefore, in order to solve the above-mentioned problems, the present applicant has disclosed in Japanese Patent Application No. 60-126868 a scale that digitally displays weight using a pressure detector consisting of a silicon diaphragm type pressure sensor. Although such pressure detectors are small, highly sensitive, and highly accurate, in order to more accurately measure minute or relatively large weights, the pressure acting on the pressure detector must be proportional to the weight of the object to be measured. Sometimes it is desirable to amplify or attenuate the signal.

[Purpose of the invention]

An object of the present invention is to provide a scale that can further improve measurement accuracy by using a lever piece.

[Disclosure of the invention]

An embodiment of the scale of the present invention will be described below with reference to the drawings, taking as an example a case in which the scale of the present invention is formed into a spoon shape.

In FIGS. 1 to 6, the balance 1 of the present invention has a lever piece 6 having a holding part 2 at its tip for holding an object to be measured. A pressure detector 9 which is applied with pressure approximately in proportion to the weight W by the lever piece 6 which is moved by the weight W of the object to be measured held in the body and which converts the pressure into an electrical signal, a calculation unit 10 and a display unit. 1
In addition, in this example, a power source 12 is connected to the base body 5, and when turned on, the power source 12 is energized for a short time to the pressure detector 9, the calculation section 10, and the display section 11.
A switch 13 is provided to set the display on the display section 11 to 0.

The pressure detector 9 is a silicon diaphragm type pressure sensor in this example. Note that the silicon diaphragm type pressure sensor includes a thin film-like diaphragm portion formed by etching the center portion of the back surface of the chip CH, and the diaphragm portion can be sensitively and minutely deformed due to the pressure difference between the upper and lower sides of the chip CH. Also, four resistors R1 to R4 made by diffusing boron are formed in the diaphragm, and each resistor R
1 to R4 expand and contract due to the deformation of the diaphragm, and as a result of the change in the lattice spacing of the crystal, due to the piezoresistance effect,
Its resistance value changes. Further, the resistors R1 to R4 are set to have the same resistance value, and are arranged at positions where the resistance value of the resistors R1 and R4 changes by the resistance value dr, and the resistance value of the resistors R2 and R3 changes by the resistance value -dr due to the applied pressure.

Therefore, the resistors R1 to R4 are bridge-coupled and their input terminals are
By inputting a constant voltage or constant current, the output voltage is proportional to the resistance value dr. Note that the chip CH is
It is fixed to the head r-I using a soft adhesive and wire-bonded to the leads.

Further, the head H is provided with an open hole k communicating with the back surface of the diaphragm portion.

In addition, in a silicon diaphragm pressure sensor, when the back side of the diaphragm part is set to atmospheric pressure and pressure is applied to the front side in addition to the above atmospheric pressure, when the pressure is gradually increased from 0, the pressure and output voltage are directly proportional. Hail the straight line area,
Next is the non-direct vA area. Therefore, in this example, it is used within the linear region.

Furthermore, within the linear region, an offset voltage VOF occurs in the output voltage due to errors in the resistors R1 to R4.

Furthermore, the resistance value of each resistor R1 to R4 changes due to temperature changes, but the linear region appears to move vertically in parallel. Therefore, by zero-compensating the offset before using the pressure VOF, it is possible to reduce the resistance value during short-term use. can ignore temperature changes and ensure sufficient accuracy for practical use.

As shown in FIG. 4, the pressure detector 9 has a cap C having a through hole T in the center attached to the head H, and a diaphragm 8 disposed inside the cap C. The diaphragm 8 is made of soft synthetic rubber, synthetic resin, etc. and has a hat shape along the inner surface of the cap C, and the eave portion of the periphery is sandwiched and fixed between the cap C and the head (2).

In addition, a thick part is provided in the center of the septum III 8 in alignment with the through hole T, and a small hole H having a tapered outer end is provided in the thick part. Therefore, the pressure detector 9 closes the small hole H and presses the diaphragm 8. The internal fluid, in this example air, is pressurized by the diaphragm, and the pressure can be converted into an electrical signal by deforming the diaphragm.

The base body 5 is formed into a spoon shape as described above, and consists of the movable body 3 forming the spoon body and the stationary body 4 forming the handle.

The movable body 3 has, at the tip of the lever piece 6, the holding part 2 which is made of a saucer and holds the object to be measured, and has a pusher piece 21 with a smooth spherical upper end raised at the rear end. The lever piece 6 is composed of a shaft portion 23 and a socket portion 25 into which an insertion piece 24 at the rear end of the cough shaft portion 23 is press-fitted so as to be removable.

The stationary body 4 has an inner shell shape and has an opening in its front surface into which the rear end of the lever piece 6 is inserted, and the lever piece 6 is supported by bearing pieces 26 and 26 formed in the vicinity of the opening inside the stationary body 4. The pins protruding from both sides of the socket portion 25 are pivotally supported. Therefore, the lever piece 6 can be tilted in a vertical plane,
Further, the stationary body 4 supports the movable body 3 so that the holding portion 2 can be moved up and down.

Further, in this example, the pressure detector 9, pressure transducer 7, calculation section 10, and power source 12 are housed inside the stationary body 4, and a display section 11 and a switch 13 are provided on the top surface of the stationary body 4. There is.

The pressure transducer 7 is mounted using, for example, a printed circuit board P with the small hole H facing downward and aligned with the pusher piece 21, as shown in FIG.

Furthermore, the movable body 3 is made of lightweight synthetic resin, for example, and its center of gravity is formed forward of the pivot point, so that the push piece 21 can be raised by holding the stationary body 4 horizontally. Equilibrium is maintained with the small hole H closed in advance. Moreover, by flipping up the tip of the movable body 3, the push piece 21 is lowered and the small hole 1 can be opened. Further, in the lever piece 6, the ratio Ll/L2 of the length Ll between the holding part 2 and the pivot point and the distance L2 between the pusher piece 21 and the pivot point is set to be larger than 1. Therefore, the pressure can be applied to the pressure sensor 9 in proportion to the weight 1w of the object to be measured held in the holding section 2 and amplified.

The display section 11 includes a display window 37 provided on the upper plate of the stationary body 4.
It consists of a liquid crystal display panel with, for example, seven segments arranged in three rows.

In this example, the calculation unit 10 is made of an analog circuit and includes a storage unit 15, and also includes a pressure detector 9, a pressure detector 9,
The display unit 11 is attached to the printed circuit board P and the switch 1
3. A power source 9 is connected to configure the electric circuit illustrated in FIG. The electric circuit will be explained below along with its operation.

Each of the resistors R1 to R4 of the pressure detector 9 is bridge-coupled as described above and connected between the power supply line and the earth line. Therefore, the pressure detector 9 converts the pressure of the internal fluid into an electrical signal and outputs it to the output end. Further, the output voltage is proportional to the weight W of the object to be measured, and the offset voltage VOF is an increment due to the self-weight of the movable body 3.
pressure VWO. Also, the output voltage is
It is input to 0.

The calculation section 10 includes a sensitivity adjustment section 16 consisting of an attenuator.
and a storage section 15 for storing the offset voltages VOF and WO, and the offset voltages VOF and WO stored in the storage section 15.
A subtraction unit 19 that subtracts O from the output voltage is connected in sequence. The subtraction unit 19 is composed of a differential amplifier OP2 with high input impedance, and its positive input is directly connected to the amplification unit 17, and its negative input is connected to the storage unit 1 between it and the ground line.
5 is connected to the capacitor C1, and the amplifying section 17
An analog switch 20 is arranged between the output end and the negative input. Further, the analog switch 20 operates for a certain period of time, for example, by applying a power supply voltage to the power supply line.
Turns on for a short period of about seconds.

Therefore, the arithmetic unit 10 amplifies the input voltage in the amplification unit 17 by applying the power supply voltage, and stores it in the capacitor C1 by turning on the analog switch 20. Next, the analog switch 20 is turned off, only the voltage stored in the capacitor CI is input to the negative input of the operational amplifier OP2, and an output voltage from which this voltage is subtracted is output from the output terminal.

Therefore, the calculation section 10 can output a calculation signal obtained by calculating the electrical signal converted from the pressure detector 9 into the weight ZW of the object to be measured. The calculated signal converted into the weight W of the object to be measured is an electrical signal whose value is O when the weight W is O and is directly proportional to the weight W, and in this example is also an analog signal. Further, the calculation output is converted into a digital signal by the AD converter 46 and digitally displayed by the display section 11.

Further, the arithmetic signal is adjusted by the sensitivity adjustment section 16 so that when the mold 1w weighs, for example, 10 g, the display becomes [10°0].

The power source 12 is made of a battery, and is connected to the power line and the ground line via a power circuit 47.

The power supply circuit 47 includes a capacitor C as illustrated in FIG.
It consists of a switch part 49 which turns off the connection between the mold a12 and the power supply line by the discharge of 2, and a constant voltage part 50 consisting of, for example, a three-terminal regulator. Further, the capacitor C2 is connected to a switch 13, and is charged to the power supply voltage when the switch 13 is turned on. Further, the time constant during discharging is set to be relatively large, and the switch section 49 is turned on for a short time of about one to several minutes. Note that the calculation unit 10, the AD converter 46, the power supply circuit 47, and the like are formed as a one-chip IC, except for a large-capacity capacitor.

Therefore, when the switch 13 is turned on, the power supply 12 is connected to the power supply line, and the pressure transducer 7, the calculation section 10, and the display section 11 are connected to each other.
and the AD converter 46 can be energized for a short time. Also switch 1
3, by energizing the arithmetic unit 10, the arithmetic unit 10 is driven, the analog switch 20 is turned on, and the display on the display unit 1 can be set to O. In this example, the display can be set to 0 before and after holding the object to be measured, and only the increase or decrease after measurement can be displayed.

[Effect]

However, the scale 1 scoops cooking ingredients etc. with the holding part 2,
It can be used in the same way as a traditional spoon, such as for mixing and transferring.

Further, the holding part 2 can be easily cleaned or replaced by removing the insertion piece 24 from the socket/throat part 25.

In addition, the balance 1 holds the stationary body 4 horizontally prior to measurement. At this time, the holding part 2 of the movable body 3 is lowered by its own weight, and the pushing piece 2 relatively pushes up the diaphragm 8 by its own weight while closing the small hole H. The internal fluid is therefore pressurized and has a resistance R
1 to R4 change.

By turning on the switch 13 in such a state,
The calculation unit 10 can set the display unit 11 to 0 and the pressure detector 9
Temperature compensation can be omitted, the weight of the movable body 3 and its errors can be absorbed, and usability can be improved. Further, after the display becomes O in this way, the increased pressure is converted into an electrical signal by the pressure detector 9 by holding the object to be measured in the holding part 2. Further, the calculation section 10 calculates the increase, and the display section 11 digitally displays the increase as a number representing the weight W.

Further, the power supply circuit 47 can automatically turn off the power after a certain period of time has elapsed, thereby preventing consumption of the power supply 12.

FIG. 7 shows another embodiment of the present invention in which the scale 1 is formed as a ladle, and in this embodiment, the movable body 3 forms a holding part 2 via a support shaft 22 perpendicular to the tip of the lever piece 6. The ratio L1/L2 of the length Ll between the holding portion 2 and the pivot point and the length L2 between the push piece 21 and the pivot point is set to be smaller than 1. Therefore, even for objects to be measured whose weight W is relatively large,
The weight 1w attenuates and pressurizes the pressure detector 9, allowing accurate measurement.

The scale 1 of the present invention can be formed into any arbitrary shape, such as a spoon, a ladle, a tabletop type, or a letter scale having a holding part 2 made of a clip. As shown in FIG. 8, the pressure detector 9 can omit the small hole I (as shown in FIG. 8), and in addition to the silicon diaphragm type pressure sensor, a piezoelectric type, capacitance type pressure sensor, etc. can also be used. In addition to configuring the calculation section 10 using an analog circuit, the electric circuit can also be configured using a digital circuit such as a so-called one-chip microcomputer.Also, the calculation section 10 can perform calculations that convert the weight into duram units. In addition to outputting only a signal, it is also possible to output a calculated signal converted to the weight of other units, such as bonds.Also, the display section 11 can display time (time or packing time) or postage ( In addition, various liquids other than air can be used as the internal fluid 6, and the scale of the present invention can be modified into various forms.

〔Effect of the invention〕

As described above, the scale of the present invention has a base body that tiltably supports a lever piece having a holding part that holds an object to be measured, and a lever piece that tilts depending on the weight of the object held in the holding part. Since it is equipped with a pressure detector that applies pressure approximately in proportion to the weight W, a calculation section, and a display section,
The device can be made smaller, the weighing accuracy can be improved, and reading errors can be eliminated by digital display. Furthermore, the lever piece can amplify or attenuate the pressure applied to the pressure detector, further improving measurement accuracy.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an embodiment of the scale of the present invention in the form of a spoon, Fig. 2 is a sectional view thereof, Fig. 3 is a sectional view of its main parts, and Fig. 4 is its sectional view. 5 is an electrical diagram used in the present invention, a block diagram showing the paths, and FIG. 6 is a wiring diagram illustrating the power supply circuit.
FIG. 7 is a sectional view showing another embodiment of the present invention, and FIG. 8 is a sectional view showing another example of the pressure transducer. 2--Holding section, 5--Base body, 6--Lever piece, 9--Pressure detector, 10--Calculating section, Work 1--Display section.

Claims (1)

[Claims] (1) A lever piece having a holding part at its tip that holds the object to be measured is attached to a base that supports the lever piece tiltably in a vertical plane, and the lever piece is tilted by the weight of the object held by the holding part. A pressure detector that applies pressure approximately in proportion to the weight and converts the pressure into an electrical signal; a computing section that can output a computed signal obtained by converting the electrical signal into the weight of the object to be measured; and a digital display of the computed signal. A scale with a display section.