JPS63201543A - Strain gauge type scale - Google Patents

Abstract

PURPOSE:To measure a load with high resolution and high accuracy without using any high-accuracy circuit components by selecting and using one of plural stain inducing parts which differ in strain quantity to the same load according to a measured load. CONSTITUTION:A load cell 11 consists of a restriction part 12, a weighing part 13, and plural strain inducing parts 14a-14d, and 15a-15d which differ in strain quantity to the same load. When a load is placed, the strain inducing parts 14a-14d, and 15a-15d generate strains proportional to the magnitude of the load and the strains are converted by strain gauges 16a-16d, and 17a-17d into electric outputs. One of the strain inducing parts 14a-14d, and 15a-15d is selected and used according to the measured load by switching scaled quantities by a scaled quantity switching means.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a strain gauge scale used in weight scales and the like.

2. Description of the Related Art A conventional strain gauge type scale is constructed as shown in Figs. 10 to 12. Figure and 11th
In the figure, reference numeral 1 denotes a load cell, including a restraint section 2, a weight section 3, and a load cell. It basically consists of strain generating parts 4a to 4d, and when a load is applied, a strain proportional to the magnitude of the load is generated in the strain generating parts 4a to 4d, and the strain is converted into an electrical output by strain gauges 5a to 5d. be.

FIG. 12 is a block diagram showing the electric circuit configuration of the strain gauge type scale. In FIG. 12, 5a to 5d are full-bridge strain gauges, and 6 is the electrical circuit of the full-bridge strain gauges 5a to 5d. An amplifier for voltage amplifying the output, 7
8 is an A/D converter that converts the analog signal, which is the voltage amplified by the amplifier 6, into a digital signal; 8 is the A/D converter;
A microcomputer 9 that processes the digital signal from the D converter 7 is a display section that is driven by the microcomputer 8 and displays, for example, two images as a unit of weight.

The strain gauge type scale constructed as described above amplifies the electrical output of the full bridge strain gauges 5a to 5d by the amplifier 6, and outputs the analog signal which is the voltage amplified by the amplifier 6. The A/D converter 7 converts the digital signal into a digital signal, and the microcomputer 8 processes the digital signal and displays it on the display 9 as a unit of weight, for example, 2 to 9.
It is displayed as follows.

Problems to be Solved by the Invention With the strain gauge type scale configured as described above, weighing weights up to 19 are displayed in 10a units, and 1 to 2 are displayed in units of 2.
When it is necessary to increase measurement accuracy by displaying light items in small units, as is often the case with 01 units, or when the unit for adult scales is 500f and the unit for baby scales is 50f.
If you need a display unit that matches the weight, such as f units, we have a complete set of scales with a scale of 150 and 9 and a display unit of 500F (for adults) and a scale of 15 and a display unit of 50g (for babies). An easy solution for constructing a stand-alone configuration is to increase the amplification factor of the amplifier 6 by 10 times, but in this case, the electrical output of the strain gauges 5a to 5d is the same, but the amplification factor is increased by a factor of 'tlO. ,noise.

Drifts due to temperature changes are all 10 times larger, so the circuit components of the amplifier 6 (op-amp, resistor, etc.) need to have ultra-low drift, making the circuit components extremely expensive, and increasing the amplification factor by reducing noise. When a filter is used, the noise filter also needs to be a high-quality product, which also has the drawback of increasing the cost of circuit components.

The present invention eliminates the above-mentioned drawbacks, and its purpose is to be able to perform high-resolution and high-precision load measurements without using ultra-high precision circuit components, and to reduce the cost of circuit components. The purpose of the present invention is to provide a strain gauge type scale that can be used as a strain gauge.

Means for Solving the Problems The present invention provides a load cell 11 having a plurality of strain-generating portions 14a to 14d, 15a to 15dt with the same load and different amounts of strain.
and a plurality of strain generating parts 14a to 1 of the load cell/L/11.
4d, 15a to 15d is selectively used according to the measured load, and weighing switching means is provided for switching the weighing amount.

action A plurality of strain generating parts 14a to 14d of the load cell Iv11.

Generating different amounts of strain with the same load on 15a to 15d,
A plurality of strain generating parts 14a to 14d, 1 of the load cell 11
One of 5a to 15d is selected and used according to the measured load by switching the weighing amount with a weighing switching means, and high-resolution and high-precision load measurement is performed without using ultra-high precision circuit parts.

Embodiment An embodiment of the strain gauge type scale of the present invention is shown in Figs. 1 to 9 below.
This will be explained with figures.

The load cell of the strain gauge type balance of the present invention is constructed as shown in FIGS. 1 to 3, and in FIGS. Plural strain-generating parts 14a, 14b, 1 with different amounts of strain under the same load
4c, 14d, 15a, 15b, 15cm 15d, and when a load is applied, strain proportional to the magnitude of the strain occurs in the strain-generating parts 14a to 14b and 15a to 15d.
The strain generated in the strain gauges 16a to 16d and 17a
17d to convert into electrical output.

In the above case, for example, in the case of a weight scale, the strain-generating parts 14a to 1
4d is the strain generating part of the weighing scale for adults and is 150KIi+, strain generating parts 15a to 15d are strain generating parts for babies and is 15mm, and strain gauges 16a to 16d and 17a to 17d are respectively
is converted into electrical output at

Further, the amount of strain in the strain generating parts 14a to 14d and 15a to 15d is approximately determined by the thickness of the load cell 11 shown by A in FIG. 3, and conversely, the amount of strain is determined by the size of the round hole 19.

FIG. 4 is a block diagram showing the electric circuit configuration of one embodiment of the strain gauge type scale of the present invention.
7d is a full-bridge strain gauge; 20 is an amplifier for voltage amplifying the electrical output of the full-bridge strain gauges 16a to 16d; and 21 is a full-bridge strain gauge.

an amplifier for voltage amplifying the electrical outputs of 17a to 17d;
22 is an analog switch that alternately switches the switching contacts 22a and 22b by a microcomputer 23; 24 is an A/D converter that converts the analog signal from the analog switch 22 into a fully digital signal; 23 is the analog switch from the A/D converter 24; a microcomputer that processes the digital signals and alternately switches the switching contacts 22a and 22b of the analog switch 22;
The display section is driven by the 25 microcomputer 23 and displays, for example, 2 to 2 as the unit of weight.

Next, the operating state of the strain gauge type scale configured as described above will be explained.

First, the operation of the strain-generating portion of the load cell is, for example, load cell 1.
The case where a load of 0 to 15 kg or more is applied to 1 is explained with reference to FIGS. 5 to 8. When the load is oKP, as shown in FIG.
If no strain occurs in 15a to 15d and the load is up to 15Kg, the situation will be as shown in Figure 6, and if the load is 15KIF to 1
If the load is up to 50Kg, it will be as shown in Figure 7, and the load 1
In the case of 50 threats or more, the situation is as shown in FIG.

In addition, stoppers (for example, stopper 27a for adults and stopper 27b for babies) 27a are provided at the lower portions of the strain-generating parts 14a to 14d and 15a to 15d, respectively, for overload protection.
, 27b are installed.

For example, if we assume a load of 5KF in the state shown in Figure 5,
The output of the strain gauges 16a to 16d shown in Fig. 4 is 50μ.
The v1 strain gauges 17a and 17b generate an output of 500 μV.

Next, assuming a load of 50Kp in the operating state shown in Fig. 7,
The operation of the circuit configuration shown in FIG. 4 is such that the outputs of the strain gauges 17a to 17d are protected by the stopper 27b and are 1500 #V, and the outputs of the strain gauges 16a to 16b (17) are 500 μV, and each amplifier 20.21 has the same amplification factor. The microcomputer 23 switches the switching contacts 22a and 22b of the analog switch 22 to apply the voltage amplified voltage to the A/D converter 24. , the A/D converter 24 converts the analog signal into a digital signal, and the A/D converter 2
4, the digital signal is processed by the microcomputer 23 and soKg is displayed on the display section 25.

In the above case, the analog switch 22 is
Switching contacts 22a, 22btON10FF to switch each (for example, if it is a weight scale, switch between adult/baby) f
: Do it.

In the above case, the strain-generating parts 14a to 14d are actually strain-generating parts.

Fine adjustment of the amplification factor is required due to variations in the wall thickness of 15a to 15d, variations in strain gauges 16a to 16d, 17a to 17d, etc., but the amplification factors are about the same for each, and the operational amplifiers, resistors, etc. used are Parts with similar characteristics are fine.

The above operation is shown in the graph of FIG.

Effect of the invention.

Since the strain gauge type scale of the present invention has the above configuration,
High-resolution, high-precision load measurement can be performed without using ultra-high precision circuit components, and the cost of circuit components can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a load cell showing one embodiment of the strain gauge type scale of the present invention, FIG. 2 is a front view of FIG. 1, and FIG.
FIG. 4 is a block diagram showing the electrical circuit configuration of an embodiment of the strain gauge type scale of the present invention, and Figures 5 to 8 are the load cells of the strain gauge type scale of the present invention. FIG. 9 is an output-load graph showing the operation of the strain gauge scale of the present invention; FIG. 10 is a perspective view of the load cell of the conventional strain gauge scale; FIG. 11 1 is a schematic configuration diagram of a conventional strain gauge type scale, and FIG. 12 is a block diagram showing an electric circuit configuration of one embodiment of the conventional strain gauge type scale. In the drawing, 11 is a load cell, and 14a to 14d. 15a to 15d are strain generating parts, and 22 is an analog switch. Agent Patent Attorney Takeshi Sugiyama (1 other person) IJ Figure 1 Figure 2 Figure 3 Figure 1O Figure 1I Figure 12

Claims (1)

[Claims] 1. Equipped with a load cell having a plurality of strain generating parts with the same load and different amounts of strain, and a weighing switching means for selectively using one of the plurality of strain generating parts of the load cell according to the measured load and switching the weighing amount. A strain gauge type scale characterized by: