load cells

Abstract

The application discloses a kind of load cell, including Wheatstone bridge, the excitation end of the Wheatstone bridge is connected with several compensation modules in series, the compensation module includes strain gauge and temperature compensation module group connected to the strain gauge in parallel, the temperature compensation module group includes several temperature compensation modules in series or parallel, the temperature compensation module includes thermistor in series or parallel, alternatively, includes several thermistors and several fixed resistors, and the thermistor and the fixed resistor are in series or parallel.The load cell of the application, the temperature compensation module is compensated to the strain gauge for non-linear compensation, so as to realize the temperature error in the non-linear error compensation of the load cell, and further improve the weighing precision and the weighing performance of the load cell.

Description

Technical Field

[0001] The invention relates to a weighing sensor for weighing. Background Art

[0002] Currently, load cells contain nonlinear errors, especially column-type load cells. Due to their unique structure, these cells exhibit significant nonlinear errors, typically exceeding 1400ppm. Therefore, load cells typically use strain gauges to compensate for nonlinear errors, particularly semiconductor strain gauges, to compensate for linear errors.

[0003] However, strain gauges have a temperature coefficient (TC), which introduces TC errors during nonlinear compensation, reducing weighing accuracy. In particular, semiconductor strain gauges are based on P-type silicon crystals, which have a large temperature coefficient of resistance (TCR) and a temperature coefficient of sensitivity (TCK). This results in significant TC errors during nonlinear compensation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in order to overcome the problem of reduced weighing accuracy caused by the introduction of temperature coefficient error in the nonlinear compensation of a weighing sensor in the prior art, a weighing sensor is provided, which improves the weighing accuracy and measurement performance by introducing temperature compensation in the nonlinear compensation.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The present invention provides a weighing sensor including a Wheatstone bridge. The sensor is characterized in that a plurality of compensation modules are connected in series to an excitation end of the Wheatstone bridge. The compensation modules include a strain gauge and a temperature compensation module group connected in parallel to the strain gauge. The temperature compensation module group includes a plurality of temperature compensation modules connected in series or in parallel.

[0007] The temperature compensation module includes thermistors connected in series or in parallel, or includes a plurality of thermistors and a plurality of fixed resistors, wherein the thermistors and the fixed resistors are connected in series or in parallel.

[0008] In this invention, temperature compensation is adjusted using a thermistor, or a thermistor and a fixed resistor, so that when the load cell's temperature changes, the resistance change rate of the strain gauge used for nonlinear compensation and the resistance change rate of the temperature compensation module are balanced. This achieves the purpose of compensating for temperature errors in the load cell's nonlinear error compensation.

[0009] The strain gauge parallel temperature compensation module group of the present invention realizes the balanced setting of the resistance change rate of the strain gauge and the resistance change rate of the temperature compensation module, and realizes the precise setting and control of the resistance of the temperature compensation module by connecting multiple temperature compensation modules in series and in parallel.

[0010] The temperature compensation module of the present invention further connects thermistors and fixed resistors in series or in parallel to achieve precise setting and control of the resistance of the temperature compensation module. The connection of thermistors and fixed resistors in series or in parallel in the present invention can refer to the connection of all thermistors and fixed resistors in parallel or in series, the connection of multiple resistor groups consisting of any number of thermistors and any number of fixed resistors in parallel, the connection of two resistor groups consisting of all thermistors and all fixed resistors connected in parallel, or the connection of two resistor groups consisting of all thermistors and all fixed resistors connected in series in parallel, to achieve precise setting and control of the resistance of the temperature compensation module in different forms and methods.

[0011] The fixed resistor of the present invention is a resistor with a fixed resistance value and is not affected by temperature or is only slightly affected by temperature. The thermistor of the present invention is a resistor with a resistance value that changes with temperature.

[0012] Preferably, the strain gauge is a semiconductor strain gauge.

[0013] Preferably, the weighing sensor further comprises an elastic element, and the strain gauge is arranged on the surface of the elastic element, for converting the deformation of the elastic element into a resistance value to compensate for nonlinear errors.

[0014] Preferably, the thermistor is arranged on the surface of the elastic element.

[0015] The present invention converts the temperature change of the elastic element into the change of the resistance value of the resistor with a temperature coefficient by arranging the thermistor on the surface of the elastic element.

[0016] Preferably, the weighing sensor is a column-type weighing sensor.

[0017] Preferably, the compensation module includes a strain gauge and a thermistor connected in parallel to the strain gauge.

[0018] Preferably, the compensation module includes a strain gauge, and a thermistor and a fixed resistor respectively connected in parallel to the strain gauge.

[0019] Preferably, the compensation module includes a strain gauge, and a thermistor and a fixed resistor connected in series, and the thermistor and the fixed resistor are connected in parallel to the strain gauge.

[0020] The positive progress effect of the present invention is:

[0021] The weighing sensor of the present invention performs corresponding temperature compensation on the strain gauge used for nonlinear compensation through the temperature compensation module, thereby compensating the temperature error in the nonlinear error compensation of the weighing sensor, thereby improving the weighing accuracy and measurement performance of the weighing sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a weighing sensor according to embodiment 1 of the present invention

[0023] Figure 2 Schematic diagram of a compensation circuit according to embodiment 1 of the present invention.

[0024] Figure 3 FIG. 1 is a schematic diagram of a compensation circuit according to embodiment 2 of the present invention.

[0025] Figure 4 Schematic diagram of a compensation circuit according to embodiment 3 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0027] The present invention connects a thermistor in parallel to a nonlinear compensation strain gauge of a weighing sensor to achieve temperature compensation for the strain gauge, thereby improving the weighing accuracy.

[0028] The following embodiments are used to illustrate the implementation of the present invention.

[0029] Example 1

[0030] like Figure 1 The elastic element of the column-type load cell shown in FIG. The cross-sectional shape of the elastic element can be any shape, such as a circular cross-section, a square cross-section, or an H-shaped cross-section. A Wheatstone bridge 11, a semiconductor strain gauge 12 for nonlinear compensation, and a thermistor 13 are provided on the surface of the elastic element of this embodiment.

[0031] The Wheatstone bridge 11 is used to convert the deformation of the elastic element into a change in the resistance of the strain gauge. The semiconductor strain gauge 12 also converts the deformation of the elastic element into a change in the resistance of the semiconductor strain gauge, thereby providing nonlinear compensation for the resistance of the Wheatstone bridge 11. The thermistor 13 converts the temperature change of the elastic element into a change in the resistance of a resistor with a temperature coefficient.

[0032] The compensation circuit structure of this embodiment is as follows Figure 2As shown, resistors SG1, SG2, SG3, and SG4 form a Wheatstone bridge 11. A semiconductor strain gauge SE is connected in series to the excitation terminals +Ext and -Ext of the Wheatstone bridge 11, respectively. Signals are output from the signal output terminals +Sig and -Sig of the Wheatstone bridge 11. Each semiconductor strain gauge SE is connected in parallel with a thermistor NiC. The semiconductor strain gauge SE and the parallel thermistor NiC form a compensation module.

[0033] When the temperature of a column load cell changes, the resistance change rate ΔR / R of the semiconductor strain gauge SE will also change significantly due to the influence of its temperature coefficient of resistance (TCR) and temperature coefficient of sensitivity (TCK). The resistance change rate ΔR / R of the thermistor NiC connected in parallel across the semiconductor strain gauge SE will also change accordingly. By balancing the resistance change rates of the semiconductor strain gauge SE and the thermistor NiC, the combined resistance change rate of the semiconductor strain gauge SE and the thermistor NiC is unaffected by temperature, thereby accurately compensating for the nonlinear error of the column load cell.

[0034] In another embodiment, a plurality of thermistors NiC are connected in parallel to the semiconductor strain gauge SE. For example, two or four thermistors NiC are connected in parallel to each semiconductor strain gauge SE.

[0035] In another embodiment, multiple thermistors NiC are connected in series and then connected in parallel to the semiconductor strain gauge SE. For example, two or four thermistors NiC are connected in series, and both ends of the series thermistors NiC are connected in parallel to both ends of the semiconductor strain gauge SE.

[0036] Example 2

[0037] In the weighing sensor of this embodiment, the Wheatstone bridge, the semiconductor strain gauge for nonlinear compensation, and the thermistor are also arranged on the surface of the elastic element. Their arrangement and connection methods are the same as those in Example 1. The difference between this embodiment and Example 1 is that:

[0038] like Figure 3 As shown, in this embodiment, a fixed resistor R is further connected in parallel to each thermistor NiC, and the thermistor NiC and the fixed resistor R connected in parallel therewith form a temperature compensation module, so as to further achieve accurate setting and control of the resistance of the temperature compensation module.

[0039] In another embodiment, a plurality of temperature compensation modules are connected in series, and the plurality of temperature compensation modules connected in series are further connected in parallel with the semiconductor strain gauge SE.

[0040] In a modified embodiment, the temperature compensation module includes multiple thermistors NiC and fixed resistors R connected in parallel, for example, a temperature compensation module composed of one thermistor NiC connected in parallel to two fixed resistors R, or two thermistors NiC connected in parallel are connected in parallel to two fixed resistors R, or two thermistors NiC connected in series are connected in parallel to two fixed resistors R connected in series.

[0041] In another embodiment, a plurality of temperature compensation modules as described in the modified example are connected in series, and the plurality of temperature compensation modules connected in series are further connected in parallel with the semiconductor strain gauge SE.

[0042] Example 3

[0043] The structure of the weighing sensor of this embodiment is the same as that of embodiment 2, and the difference between the weighing sensor and embodiment 2 is that:

[0044] like Figure 4 As shown, in this embodiment, each thermistor NiC is further connected in series with a fixed resistor R, and the thermistor NiC and the fixed resistor R connected in series with it form a temperature compensation module. This further achieves accurate setting and control of the resistance of the temperature compensation module.

[0045] In another embodiment, a plurality of temperature compensation modules are connected in parallel, and the plurality of temperature compensation modules connected in parallel are further connected in parallel with the semiconductor strain gauge SE.

[0046] In a modified embodiment, the temperature compensation module includes multiple thermistors NiC and fixed resistors R connected in series, for example, a temperature compensation module consisting of one thermistor NiC connected in series with two fixed resistors R. Alternatively, two thermistors NiC connected in series are further connected in series with two fixed resistors R.

[0047] In yet another embodiment, a plurality of temperature compensation modules as described in the modified example are connected in parallel, and the plurality of temperature compensation modules connected in parallel are further connected in parallel with the semiconductor strain gauge SE.

[0048] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A weighing sensor comprising a Wheatstone bridge, characterized in that: The excitation end of the Wheatstone bridge is connected in series with a plurality of compensation modules, the compensation modules including a strain gauge and a temperature compensation module group connected in parallel to the strain gauge, the temperature compensation module group including a plurality of temperature compensation modules connected in series or in parallel, The temperature compensation module includes thermistors connected in series or in parallel, or includes a plurality of thermistors and a plurality of fixed resistors, wherein the thermistors and the fixed resistors are connected in series or in parallel; The compensation module further includes a thermistor and a fixed resistor respectively connected in parallel to the strain gauge; or the compensation module further includes a thermistor and a fixed resistor connected in series, and the thermistor and the fixed resistor connected in series are connected in parallel to the strain gauge.

2. The weighing sensor according to claim 1, wherein The strain gauge is a semiconductor strain gauge.

3. The weighing sensor according to claim 1, wherein The weighing sensor further includes an elastic element. The strain gauge is arranged on the surface of the elastic element and is used to convert the deformation of the elastic element into a resistance value to compensate for nonlinear errors.

4. The weighing sensor according to claim 3, wherein The thermistor is arranged on the surface of the elastic element.

5. The weighing sensor according to claim 1, wherein The weighing sensor is a column type weighing sensor.

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