JPH06174565A - Load cell - Google Patents

Abstract

PURPOSE:To easily and quickly measure the characteristic of a bridge circuit beforehand in the stage where an output adjusting element such as a temperature compensation resistance or the like is not mounted, without temporarily installing a measuring element such as a jumper wire or the like. CONSTITUTION:A bridge circuit 10 has strain gauges 11, 12 mounted on a strain generating body 1 to generate load signals and, adjusting elements 13, 14 for adjusting the level of the load signals. In addition to input/output lead wires 15, 16 of the bridge circuit 10, there is provided a bypass wire 18 which detachably connects a connecting terminal 14a connected with the adjusting elements 13, 14 to a measuring element 21 of a preliminary measuring device 9. At the preparatory measurement, the measuring element 21 is connected to the connecting terminal 14a via the bypass wire 18, and therefore it becomes not necessary to temporarily install an element for measurement. Accordingly, the preparatory measurement can be easily and quickly performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load cell used for weighing various articles, and more specifically, a strain gauge bridge circuit, a span temperature characteristic compensation resistor and a zero point temperature characteristic compensation resistor, The present invention relates to a technique of previously measuring and testing the output characteristics of a load cell in a state before mounting an adjusting element for adjusting the level of a load signal such as a zero-point adjusting resistor.

[0002]

2. Description of the Related Art A general load cell of this type, as shown in FIG. 4, is a Roberval type strain-generating body 1 which causes strain in accordance with a load applied, and although omitted in FIG. A strain gauge 2 attached to the strain body 1 to generate a load signal
A, 2B and a bridge circuit 10 having adjusting elements such as temperature characteristic compensating resistors for spans, temperature characteristic compensating resistors for zero points, and zero point adjusting resistors for adjusting the levels of their load signals. There is. This load cell has
One end of the flexible printed wiring board 5 is attached. This flexible printed wiring board 5 has a resin-made flexible board 4 on which the input / output lead wires 3a and 3b of the bridge circuit 10 and the lands 6 for mounting the adjusting elements are formed like copper foil. It is formed by patterning with a different metal foil.

When the output characteristics of the load cell as described above are measured and tested by a pre-measuring device before the adjustment element is mounted, conventionally, the lands 6, 6 are used.
Then, for example, a jumper wire or an element 7 for measurement such as a predetermined temperature-sensitive resistance is temporarily connected (temporarily mounted) by soldering or the like, and then a connector 8 attached to the other end of the flexible printed circuit board 5 is used. Was connected to the connector 9 of the pre-measurement device for pre-measurement. After the measurement, an adjusting element that matches the measured circuit characteristic is selected and mounted, and the output of the load cell is adjusted appropriately.

[0004]

In the case of the above-described conventional pre-measurement method, it is necessary to provisionally mount the element 7 dedicated to measurement, and after the measurement, the element 7 dedicated to measurement.
It is necessary to perform a laborious and costly operation such as removing the lands 6 and 6 from the lands 6 and 6 and then mounting a predetermined adjusting element on the lands 6 and 6. As a result, there has been a problem that the adjustment cost of the entire load cell increases.

The present invention has been made in view of the above-mentioned circumstances, and only by adding an extremely simple structure, it is possible to quickly and inexpensively perform a predetermined preliminary measurement without temporarily mounting a measurement-dedicated element. It is an object of the present invention to provide a load cell that can be used.

[0006]

In order to achieve the above object, a load cell according to the present invention comprises a strain-generating body which causes strain according to a load applied thereto, and a load signal which is mounted on the strain-generating body. In a load cell having a strain gauge for generating and a bridge circuit having an adjusting element for adjusting the level of the load signal, in addition to the input / output lead wires of the bridge circuit, a connection terminal to which the adjusting element is connected Is provided with a bypass line for detachably connecting to the measuring element provided in the pre-measuring device.

[0007]

According to the present invention, when the load cell is connected to the pre-measurement device and pre-measurement is performed without mounting the adjustment element, the measurement element is connected to the connection terminal to which the adjustment element is connected. The connection terminal is connected to the element for measurement provided in the pre-measurement device through the bypass line without performing so-called temporary mounting.
Predetermined pre-measurement can be done easily. Then, at the time of mounting after the preliminary measurement, a predetermined adjusting element is connected between the connection terminals at both ends of the adjusting element to complete the bridge circuit.
When the load cell is removed from the pre-measuring device, the bypass line is open.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a bridge circuit of a load cell according to the present invention.
Of the bridge circuit 10 and the strain gauge 11 on the tension side and the strain gauge 12 on the compression side that are mounted on the strain-generating body 1 (see FIG. 4) that generates strain according to the applied load to generate a load signal. It is composed of zero-point adjusting resistors (precision resistors) 13 and 13 and zero-point temperature characteristic compensating resistors (temperature-sensitive resistors) 14 and 14 which are connected to two sides as adjusting elements. The zero-point adjusting resistor 13 adjusts the value of the zero point to a target level, and the zero-point temperature characteristic compensating resistor 1
Reference numeral 4 is for compensating for the zero point drift due to temperature change. As described later, one or both of the zero-point temperature characteristic compensating resistor 14 and the zero-point adjusting resistor (precision resistor) may be omitted.

One end of a flexible printed wiring board 17 is adhered to the flexure element 1 as in the conventional example shown in FIG. This flexible printed wiring board 1
7, a pair of connection terminals (lands) 13 for mounting the input lead wire 15 and the output lead wire 16 connected to the bridge circuit 10 and the zero point adjustment resistor 13 are provided.
a, 13b, a pair of connection terminals 14a, 14b for mounting the zero-point temperature characteristic compensating resistor 14, the bypass line 18 connected to one of the connection terminals 14a, and the like, a flexible substrate (FIG. 4) is formed of a metal foil such as a copper foil provided above. In the flexible printed wiring board 17, the connector 8 attached to the other end is used as the connector 9 of the pre-measurement device at the time of pre-measurement, and at the time of actual use, the main wiring board having the signal processing circuit is provided. The connectors 90 are respectively coupled.

In the load cell having the above structure, the zero point adjusting resistor 13 and the zero point temperature characteristic compensating resistor 1 are provided.
3, 14 are connected terminals 13a, 13b at both ends,
Bridge circuit 1 before mounting between 14a and 14b
When measuring the output characteristic of 0 in advance, the connector 8 at the other end of the flexible printed wiring board 17 is connected to the connector 9 of the pre-measurement device. As a result, the input voltage is applied to the connection points a and b of the bridge circuit 10, and the output signal is taken out from the connection points c and d via the output lead wire 16. On the other hand, the connector 9 of the pre-measurement apparatus is provided with a short-circuit wire 21 as an element for measurement, and the short-circuit wire 21 short-circuits the connection terminals 14a and 13b. In this state, the output characteristic of the bridge circuit 10 is measured in advance. Based on the measurement result, the zero-point adjusting resistor 13 and the zero-point temperature characteristic compensating resistor 14 suitable for the output characteristic of the bridge circuit 10 are selected.

As a result of the preliminary measurement, when the zero balance of the bridge circuit 10 is relatively good, one or both of the zero-point adjusting resistor 13 and the zero-point temperature characteristic compensating resistor 14 are used as adjusting elements. Both are unnecessary. In that case, it suffices to connect a conductive wire instead of these resistors to between the connection terminals 13a and 13b and between 14a and 14b.

When the load cell is to be ready for practical use after the above-described pre-measurement, the zero-point adjusting resistor 13 selected to match the output characteristics of the bridge circuit 10.
The zero point temperature characteristic compensating resistor 14 is mounted between the connection terminals 13a and 13b and between the connection terminals 14a and 14b. In this way, the finished product of the load cell in which the temperature is compensated at the zero point is obtained without the need for the troublesome labor and work cost associated with the temporary mounting such as temporary connection (temporary mounting) and removal of the measurement element. Before or after the completion of the load cell, the connector 8 on the load cell side is removed from the connector 9 on the pre-measurement device side. As a result, the bypass line 18 is opened.

In actual use, the completed load cell has its connector 8 coupled to the connector 90 of the main wiring board having the signal processing circuit. The connector 90 is open between the bypass wire 18 and the output lead wire 16. The completed load cell is usually connected to an output inspection device and inspected before actual use. The connector of the output inspection device is usually the connector 9 of the main wiring board.
It has the same wiring as 0. As a connector of this output inspection device, a bypass wire 18 and an output lead wire 16 are used.
If a short circuit is used between the two, it is possible to perform a defect diagnosis check due to disconnection.

FIG. 2 shows a case where the zero-point adjusting resistor 13 is connected to two sides on one side of the bridge circuit 10 and the zero-point temperature characteristic compensating resistor 14 is connected to the other two sides. In this case, the connection terminal 13a of the zero point adjustment resistor 13 and
By-pass lines 18 are connected to the connection terminals 14a of the zero-point temperature characteristic compensating resistors 14 one by one.
Corresponding to, a short-circuit wire 21 is provided on the connector 9.

FIG. 3 shows an embodiment in which a span temperature characteristic compensating resistor (temperature sensitive resistor) 22 is connected to the bridge circuit 10. The temperature compensating resistor 22 is connected to the input side of the bridge circuit 10, and the bypass line 18 is connected to one of the connection terminals 22a and 22b at both ends thereof 22b. On the other hand, the connector 9 of the pre-measurement apparatus is provided with a predetermined temperature-sensitive resistor (measurement element) or short-circuit wire 19 for pre-measurement, and the connector 8 on the load cell side is provided.
By coupling with the connector 9 of the pre-measurement device,
The temperature-sensitive resistor or the short-circuit wire 19 is connected to the connection terminals 22a and 22b. In this state, the span temperature characteristic of the bridge circuit 10, that is, the characteristic change of the load signal due to the temperature change of the load cell is measured in advance.

In each of the above embodiments, the bridge circuit 1
Although 0 is a full bridge type in which strain gauges 11 and 12 are connected to each of four sides, the present invention can also be applied to a half bridge type in which strain gauges are provided only in two sides.

[0017]

As described above, according to the present invention, a simple structure such as providing a bypass line in addition to the input / output lead wire of the bridge circuit is added, and the measurement element is not temporarily mounted. In both cases, the pre-measurement can be performed as specified. In addition, when actually using after the pre-measurement, it is only necessary to remove the bypass line from the pre-measurement device and leave it open, so that it is possible to suppress the increase in the labor and work cost associated with the conventional temporary mounting. The adjustment of the entire load cell can be realized quickly and at low cost.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a bridge circuit of a load cell according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a bridge circuit according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a bridge circuit according to still another embodiment of the present invention.

FIG. 4 is a schematic perspective view of a main part of a conventional load cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Strain element, 10 ... Bridge circuit, 11, 12 ... Strain cage, 13 ... Zero-point adjustment resistor (adjustment element), 14 ... Zero-point temperature characteristic compensation resistor (adjustment element), 13a, 13
b, 14a, 14b ... Connection terminal, 15 ... Input lead wire,
16 ... Output lead wire, 18 ... Bypass wire, 19 ... Temperature-sensitive resistor or short-circuit wire (measurement element), 21 ... Short-circuit wire (measurement element), 22 ... Span temperature characteristic compensation resistor (adjustment element) ).

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[Procedure amendment]

[Submission date] February 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a bridge circuit of a load cell according to the present invention.
Of the bridge circuit 10 and the strain gauge 11 on the tension side and the strain gauge 12 on the compression side that are mounted on the strain-generating body 1 (see FIG. 4) that generates strain according to the applied load to generate a load signal. It is composed of zero-point adjusting resistors (precision resistors) 13 and 13 and zero-point temperature characteristic compensating resistors (temperature-sensitive resistors) 14 and 14 which are connected to two sides as adjusting elements. The zero-point adjusting resistor 13 adjusts the value of the zero point to a target level, and the zero-point temperature characteristic compensating resistor 1
Reference numeral 4 is for compensating for the zero point drift due to temperature change. As will be described later, one or both of the zero point temperature characteristic compensating resistor 14 and the zero point adjusting resistor (precision resistor) 13 may be omitted.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

In the load cell having the above structure, the zero point adjusting resistor 13 and the zero point temperature characteristic compensating resistor 14 are provided.
The connection terminals 13a, 13b, 14a,
When the output characteristics of the bridge circuit 10 are measured in advance before mounting between 14b, the connector 8 at the other end of the flexible printed wiring board 17 is connected to the connector 9 of the pre-measurement device. As a result, the input voltage is applied to the connection points a and b of the bridge circuit 10, and the connection point c and
An output signal is taken out from d through the output lead wire 16. On the other hand, the connector 9 of the pre-measurement device is provided with a short-circuit wire 21 as an element for measurement.
1, the connection terminals 14a and 13b are short-circuited. In this state, the output characteristic of the bridge circuit 10 is measured in advance. Based on the measurement result, the bridge circuit 10
The zero-point adjusting resistor 13 and the zero-point temperature characteristic compensating resistor 14 are selected according to the output characteristics of.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

In actual use, the completed load cell has its connector 8 coupled to the connector 90 of the main wiring board having the signal processing circuit. The connector 90 is open between the bypass wire 18 and the output lead wire 16. The completed load cell is usually connected to an output inspection device and inspected before actual use. The connector of the output inspection device is usually the connector 9 of the main wiring board.
It has the same wiring as 0. The main wiring of the actual machine
If the board has an analog switch,
When the connector 90 is connected to the connector 8 on the load cell side,
The bypass wire 18 and the output lead wire 16 are
If you wire so that it will be connected via a switch,
It is possible to perform a defect diagnosis check due to the disconnection of the bridge circuit 10 .

Claims (1)

[Claims] 1. A strain-generating body that causes strain in accordance with a load applied, a strain gauge that is mounted on the strain-generating body to generate a load signal, and an adjusting element that adjusts the level of the load signal. In a load cell including a bridge circuit, a bypass for detachably connecting a connection terminal to which the adjustment element is connected, in addition to the input / output lead wire of the bridge circuit, to a measurement element provided in a pre-measurement device. A load cell characterized by having a line.