Weight scale calibration method

Abstract

The invention discloses a weighing scale calibration method, which comprises the following steps: S1, taking a zero pressure value as an initial point, gradually increasing the pressure according to a constant pressure value until the full scale of a weighing scale is reached, recording the output result of the weighing scale in each pressure value state, and carrying out normalization processing on the output result to obtain a group of corresponding relations between normalized output and the pressure values; s2, selecting a plurality of weighing scales, and obtaining a corresponding relationship between a plurality of groups of normalized outputs and pressure values according to the data collected in S1; and S3, setting a nonlinear calibration formula model, training the nonlinear calibration formula model according to the corresponding relationship between the multiple groups of normalized outputs and the pressure values to obtain a nonlinear calibration formula, and replacing multi-stage calibration by directly fitting a nonlinear curve, thereby greatly shortening the calibration time and improving the production efficiency of the weighing scale.

Description

[Technical field]

[0001] The invention relates to a weight scale calibration method. [Background Technology]

[0002] The output of the pressure sensor in the weight scale is voltage. The weight scale uses ADC to measure the voltage. Ideally, the pressure on the weight scale should be linearly related to the ADC value, but in fact, the ADC value and the pressure value are nonlinear. Figure 1 shown.

[0003] In order to solve the measurement error caused by nonlinearity, the current technology uses a multi-segment calibration method to solve the problem of nonlinearity between the output of the pressure sensor and the pressure value it is subjected to. Specifically, the full scale is divided into several segments, and the output and pressure in each segment are considered to be linear. Multiple broken lines are used to approximate the actual nonlinear curve, such as Figure 2 The dotted line is the broken line after segmentation. When using it, the user selects the corresponding segment according to the output of the weighing sensor, calls the linear correspondence of the segment to calculate the pressure value of the sensor, and then converts the pressure value into a weight value to display to the user. This calibration method requires applying multiple different weights when calibrating the scale on the production line, which consumes a lot of time in the calibration process, affecting production efficiency. [Summary of the invention]

[0004] The invention overcomes the deficiencies of the prior art and provides a weight scale calibration method.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A weight scale calibration method, characterized in that:

[0007] S1, taking zero pressure value as the initial point, and gradually increasing the pressure with a fixed pressure value until the full scale of the weight scale is reached, recording the output results of the weight scale under each pressure value state, and normalizing the output results to obtain a set of corresponding relationships between normalized output and pressure value;

[0008] S2, select multiple weight scales, collect data according to S1, and obtain the corresponding relationship between multiple groups of normalized outputs and pressure values;

[0009] S3. Setting a nonlinear calibration formula model, training the nonlinear calibration formula model with the correspondence between multiple groups of normalized outputs and pressure values, and obtaining a nonlinear calibration formula.

[0010] A weight scale calibration method as described above is characterized in that the set pressure value in S1 is 10% of the full scale value.

[0011] A weight scale calibration method as described above is characterized in that: the output result of the weight scale in the zero pressure value state in S1 is recorded as A0, the output result of the weight scale in the 10% full-scale pressure value state is recorded as A1, and so on, the output result of the weight scale in the 100% full-scale pressure value state is recorded as A10.

[0012] A weight scale calibration method as described above is characterized in that: a normalization formula is set in S1 as Pn=(An-A0) / (A10-A0), where n=1, 2, 3...10, and the output results of the weight scale under each pressure value state are input into the normalization formula to obtain a set of corresponding relationships between the normalized output and the pressure value.

[0013] The method for calibrating a weight scale as described above is characterized in that: 30 weight scales are selected in S2 to obtain 30 sets of corresponding relationships between normalized outputs and pressure values.

[0014] The above-mentioned method for calibrating a weight scale is characterized in that: the nonlinear calibration formula model is Y=aP 3 +bP 2 +cP+dP -1 +e, where Y represents the pressure on the sensor, P is the normalized output result, and a, b, c, d, and e are the parameters obtained by fitting the model.

[0015] The method for calibrating a weight scale as described above is characterized in that: the corresponding relationship between the 30 sets of normalized outputs and pressure values ​​is substituted into Y=aP 3 +bP 2 +cP+dP -1 +e, a, b, c, d, and e are calculated to obtain the nonlinear calibration formula.

[0016] A weight scale calibration method as described above is characterized by: it also includes S4, storing the nonlinear calibration formula in the weight scale to be tested, and applying a pressure value to calculate the output pressure value of the weight scale to be tested. When the difference between the calculated output pressure value and the actual pressure value is less than the allowable error range value, the weight scale inspection passes.

[0017] The method for calibrating a weight scale as described above is characterized in that: in S4, a pressure value of 50% of the full scale is applied to the weight scale to be inspected by a weight machine.

[0018] A weight scale calibration method as described above is characterized in that: in S4, the output result B0 of the weight scale to be tested at zero pressure, the output result B100 at full-scale pressure, and the output result B50 at 50% of the full-scale pressure are obtained, and the normalized output value of the 50% full-scale pressure output result is calculated to obtain the full-scale output change R=B100-B0, and the normalized output value P=(B50-B0) / R is calculated, and finally P is substituted into the nonlinear calibration formula to calculate the output pressure value of the weight scale to be tested.

[0019] The beneficial effects of the present invention are:

[0020] The present invention replaces multi-segment calibration by directly fitting a nonlinear curve, applies different pressures to multiple weight scales respectively, records the output results of the corresponding pressures, obtains the corresponding relationship between multiple groups of normalized outputs and pressure values ​​after normalizing and calculating the output results, obtains the nonlinear calibration formula after training the nonlinear calibration formula model, stores the nonlinear calibration formula in the weight scale to be tested, applies a pressure value once, and judges whether the difference between the output result of the weight scale to be tested and the actual pressure value is within the allowable error range, thereby testing whether the weight scale is qualified, greatly shortening the calibration time, and improving the production efficiency of the weight scale. [Drawings]

[0021] Figure 1 It is the actual relationship diagram between ADC value output and pressure value;

[0022] Figure 2 It is a schematic diagram of a nonlinear curve of a pressure value and an ADC value output replaced by multiple broken lines in the prior art;

[0023] Figure 3 It is a schematic diagram of the nonlinear curve of the ADC value output and the pressure value fitted by the present invention. [Specific implementation method]

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0025] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly. In addition, the descriptions of "preferred", "sub-preferred", etc. in the present invention are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "preferred" or "sub-preferred" may explicitly or implicitly include at least one such feature.

[0026] A weight scale calibration method, comprising:

[0027] S1, taking zero pressure value as the initial point, and gradually increasing the pressure with a fixed pressure value until the full scale of the weight scale is reached, recording the output results of the weight scale under each pressure value state, and normalizing the output results to obtain a set of corresponding relationships between normalized output and pressure value;

[0028] Specifically, after the weight scale is reset to zero, the pressure is increased in steps of 10% of the full scale until the pressure reaches the full scale, and the output results at different pressures are recorded.

[0029] Among them, no pressure is applied to the weight scale, and the recorded output is A0; 10% of the full-scale pressure is applied, and the recorded output is A1; 20% of the full-scale pressure is applied, and the recorded output is A2; and so on, until 100% of the full-scale pressure is applied, and the recorded output is A10;

[0030] Normalize the output results. The normalization formula is:

[0031] Pn=(An-A0) / (A10-A0), where n=1,2,3...10. After normalization, a set of corresponding relationships between normalized output and pressure value will be obtained.

[0032] S2, select multiple weight scales, collect data according to S1, and obtain the corresponding relationship between multiple groups of normalized outputs and pressure values;

[0033] Specifically, 30 weight scales are randomly selected to collect the data of S1 to obtain the corresponding relationship between multiple groups of normalized outputs and pressure values.

[0034] S3, setting a nonlinear calibration formula model, training the nonlinear calibration formula model with the correspondence between multiple groups of normalized outputs and pressure values, and obtaining a nonlinear calibration formula;

[0035] Specifically, the following polynomial regression model was used:

[0036] Y=aP 3 +bP 2 +cP+dP -1 +e

[0037] Where Y represents the pressure on the sensor; P is the normalized output result; a, b, c, d, and e are the parameters obtained by fitting the model.

[0038] The normalized output and pressure values ​​obtained from multiple weight scales are used to train the model, and a nonlinear correspondence between the normalized output and the pressure value is obtained, which is called the nonlinear calibration formula. Figure 3 shown.

[0039] S4, storing the nonlinear calibration formula in the weight scale to be inspected, applying a pressure value, calculating the output pressure value of the weight scale to be inspected, and when the difference between the calculated output pressure value and the actual pressure value is less than the allowable error range value, the weight scale inspection passes;

[0040] Specifically, after obtaining the nonlinear correspondence between the normalized output and the pressure value, the steps for calibrating each weight scale to be inspected on the production line are as follows:

[0041] Do not apply any pressure to the weight scale to be tested, and obtain the zero point B0; apply full-scale pressure to the weight scale to be tested, and obtain the full-scale point B100; obtain the full-scale output change R=B100-B0, and record the full-scale output change, which is the calibration coefficient.

[0042] Apply 50% of the full-scale pressure to the weight scale to be tested, and get the output value B50. Calculate the normalized output value P = (B50-B0) / R. Substitute P into the nonlinear calibration formula to get the pressure value and compare it with the pressure value applied by the weight machine. If it is within the allowable error range, the calibration is successful.

[0043] If the error is larger than the allowable range, it indicates that the sensor characteristics are different from the normal ones and you should recalibrate using the multi-stage calibration method.

[0044] When the scale passes the inspection, when you use it for measurement again, place the scale on the ground, the scale will automatically return to zero and record the current sensor output as the zero point. When the user stands on the scale, the sensor will have an output value. This output value is used as a reference to the new zero point to calculate the change in pressure on the scale, and then divided by the calibration coefficient R for normalization. Although changes in temperature and environment can cause small fluctuations in the zero point of the sensor, according to the characteristics of the weighing sensor, small fluctuations in the zero point will not cause significant changes in the calibration curve, so the calibration coefficient R saved during calibration can be used to calculate the normalized output. Substitute the normalized output into the calibration formula to obtain the pressure applied by the human body to the scale, and finally divide the pressure value by the acceleration of gravity to get the human body weight value.

[0045] Using a nonlinear calibration curve, only one pressure application is required to the scale during production, which saves 2 to 3 pressure application times compared to traditional piecewise linear calibration and speeds up production efficiency.

[0046] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for calibrating a weight scale, characterized in that: Included S1, taking zero pressure value as the initial point, and gradually increasing the pressure with a fixed pressure value until the full scale of the weight scale is reached, recording the output results of the weight scale under each pressure value state, and normalizing the output results to obtain a set of corresponding relationships between normalized output and pressure value; S2, select multiple weight scales, collect data according to S1, and obtain the corresponding relationship between multiple groups of normalized outputs and pressure values; S3. Setting a nonlinear calibration formula model, training the nonlinear calibration formula model with the correspondence between multiple groups of normalized outputs and pressure values, and obtaining a nonlinear calibration formula.

2. A weight scale calibration method according to claim 1, characterized in that: The set pressure value in S1 is 10% of the full scale value.

3. A weight scale calibration method according to claim 2, characterized in that: In S1, the output result of the weight scale under the zero pressure value state is recorded as A0, the output result of the weight scale under the 10% full-scale pressure value state is recorded as A1, and so on, the output result of the weight scale under the 100% full-scale pressure value state is recorded as A10.

4. A weight scale calibration method according to claim 3, characterized in that: The normalization formula set in S1 is Pn=(An-A0) / (A10-A0), where n=1, 2, 3...10, and the output results of the weight scale under each pressure value state are input into the normalization formula to obtain a set of corresponding relationships between the normalized output and the pressure value.

5. A weight scale calibration method according to claim 4, characterized in that: In S2, 30 weight scales are selected to obtain 30 sets of corresponding relationships between normalized outputs and pressure values.

6. A weight scale calibration method according to claim 5, characterized in that: The nonlinear calibration formula model is Y = aP 3 +bP 2 +cP+dP -1 +e, where Y represents the pressure on the sensor, P is the normalized output result, and a, b, c, d, and e are the parameters obtained by fitting the model.

7. A weight scale calibration method according to claim 6, characterized in that: Substitute the corresponding relationship between 30 sets of normalized output and pressure value into Y=aP 3 +bP 2 +cP+dP -1 +e, a, b, c, d, and e are calculated to obtain the nonlinear calibration formula.

8. A weight scale calibration method according to claim 1, characterized in that: The method further includes S4, storing the nonlinear calibration formula in the weight scale to be inspected, applying a pressure value, and calculating the output pressure value of the weight scale to be inspected. When the difference between the calculated output pressure value and the actual pressure value is less than the allowable error range value, the weight scale inspection passes.

9. A weight scale calibration method according to claim 8, characterized in that: In S4, a pressure value of 50% of the full scale is applied to the weight scale to be tested by a weight machine.

10. A weight scale calibration method according to claim 9, characterized in that: In S4, the output result B0 of the weight scale to be tested at zero pressure, the output result B100 at full-scale pressure, and the output result B50 at 50% of the full-scale pressure are obtained, and the normalized output value of the 50% full-scale pressure output result is calculated to obtain the full-scale output change R=B100-B0, and the normalized output value P=(B50-B0) / R is calculated. Finally, P is substituted into the nonlinear calibration formula to calculate the output pressure value of the weight scale to be tested.

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