JP5403793B2 - Weight measuring device - Google Patents

Description

  The present invention relates to a weight measuring apparatus, and more particularly, to a weight measuring apparatus that can accurately measure the weight of an object to be measured even when the environmental temperature of the weight measuring apparatus changes.

  2. Description of the Related Art Conventionally, a weight measuring device that uses an object to be measured such as an object or a person on a placement unit and measures the weight thereof has been used. In the weight measuring device, a load cell is used as means for detecting the weight of the object to be measured (for example, Patent Document 1).

  In general, a load cell has a strain generating body having a strain generating portion that deforms according to the load, and an output value that is attached to the strain generating portion and changes according to deformation (expansion / contraction) of the strain generating portion. A strain gauge. A weight measuring device equipped with a load cell measures the weight of the object to be measured based on the difference between the output value from the load cell when no load is applied (so-called zero point) and the output value when the load is applied To do.

Japanese Patent Laid-Open No. 06-201438

  The above conventional weight measuring device has the same area of use, and even when it is placed horizontally, the elastic modulus of the strain gauge or strain body changes due to the temperature change of the environment where the weight measuring device is placed. There are things to do. As a result, even if the objects to be measured have the same weight, the weight measurement value measured by the weight measuring device may cause an error due to a temperature change in the environment.

  Therefore, before using the weight measuring device, the user of the weight measuring device adjusts the display value of the weight measuring device to the actual weight value by using a specimen having a known weight. There is a need to do. However, even when the instrument is adjusted at the time of shipment of the weight measuring device or before the user uses the weight measuring device, if the environmental temperature changes after that, there is a risk that an error may occur in the weight measurement value. There is. Therefore, the user needs to adjust the instrumental error every time the weight measuring device is used.

  Accordingly, the present invention provides a weight measuring apparatus capable of measuring the weight of a measurement object with high accuracy while reducing the trouble of adjusting the instrumental error by the user even if the temperature of the environment in which the weight measuring apparatus is placed is changed. The purpose is to provide.

  The weight measuring device of the present invention for solving the above-mentioned problems is a weight measuring means for measuring a weight value of an object to be measured, a temperature measuring means for measuring temperature, and a plurality of temperature measurements measured by the temperature measuring means. Value, a weight measurement value of a test specimen having a known weight value measured by the weight measuring means in each of the plurality of temperature measurement values, and an adjustment factor indicating a relationship with the known weight value of the test specimen. Storage means, and a calculation means for correcting a temperature error of the weight measurement value of the measurement object and calculating a weight adjustment value, the calculation means of the measurement object measured by the weight measurement means Using a weight measurement value, a temperature measurement value measured by the temperature measurement means in relation to the measurement of the object to be measured, and the temperature measurement value and a corresponding adjustment factor stored in the storage means Performance Characterized in that it.

  Further, the temperature measuring means in the weight measuring device of the present invention is characterized by measuring the temperature of the weight measuring device or the ambient temperature of the weight measuring device.

The adjustment coefficient in the weight measuring device of the present invention is a span coefficient that represents a relationship between the weight measurement value and the weight adjustment value in the measured temperature measurement value, and is arbitrarily selected from the two temperature measurement values. The temperature measurement values are T ₁ and T ₂ , the span coefficients corresponding to the _two temperature measurement values T ₁ and T ₂ are S ₁ and S _2, and the measured weight measurement value of the object to be measured is D _M , _Assuming that the measured temperature measurement value of the measurement target is T _M , the span coefficient S _M and the adjusted weight adjustment value W _M corresponding to the temperature measurement value T _M are expressed by the following formula S _M = S ₁ + (S _{2 -S 1) · (T M -T} 1) / (T 2 -T 1), and _{W M =} D M · _S M
It is calculated | required by.

Further, the temperature measurement values T ₁ and T _{2 in} the weight measuring device of the present invention are characterized in that they are values closest to and next to the temperature measurement values T _M.

The adjustment coefficient in the weight measuring apparatus of the present invention is a temperature correction coefficient related to a span coefficient representing a relationship between the weight measurement value and the weight adjustment value in the measured temperature measurement value, and the plurality of adjustment coefficients stored in the storage unit Two temperature measurement values arbitrarily selected from the temperature measurement values are T ₁ and T _2, and the span coefficients corresponding to the _two temperature measurement values T ₁ and T ₂ are S ₁ and S ₂ . _Assuming that the measured weight measurement value is D _M and the measured temperature measurement value of the object to be measured is T _M , the temperature correction coefficient T _COEFN for the temperature measurement value T _M and the span coefficient S corresponding to the temperature correction coefficient T _{COEF1 M} and the adjusted weight adjustment value W _M are given by the following equation: T _COEF1 = (S ₂ / S ₁ −1) / (T ₂ −T ₁ ),
S _M = S ₁ {1+ (T _M −T ₁ ) · T _COEF1 }, and W _M = D _M · S _M
It is calculated | required by.

Further, the temperature measurement value T ₁ in the weight measuring device of the present invention is the value closest to the temperature measurement value T _M , and the temperature measurement value T ₂ is the next closest value to the temperature measurement value T _M. It is characterized by being.

The adjustment coefficient in the weight measurement device of the present invention is a temperature correction coefficient related to a weight measurement value, and the storage means stores a known weight value measured by the weight measurement means in each of the plurality of temperature measurement values. A weight measurement value of the test specimen is stored, and two temperature measurement values arbitrarily selected from the plurality of temperature measurement values stored in the storage means are defined as T ₁ and T _2, and the two temperature measurement values T _1, the weight measurement value corresponding to T ₂ and D _1, D _2, when the measured weight measurements of the object to be measured D _M, the measured temperature measured value of the target to be measured and T _M, the temperature The temperature correction coefficient T _COEF2 for the measurement value T _M, the weight measurement value D _M ′ after AD conversion estimated for the known weight value W _C1 , the span coefficient S _M , and the adjusted weight measurement value D _M are given by T _{CO F2 = (D 2 / D 1} -1) / (T 2 -T 1),
D _M ′ = D ₁ {1+ (T _M −T ₁ ) · T _COEF2 },
S _M = W _C1 / D _M ′ and W _M = D _M · S _M
It is calculated | required by.

Further, the temperature measurements T ₁ and T ₂ in the weight measuring device of the present invention is characterized in that the a value close to the nearest value and the next temperature measurement value T _M.

  In the weight measuring device of the present invention, the calculation means includes the weight measurement value measured by the weight measurement means in an unloaded state and the weight measurement value measured by the weight measurement means in the no-load state. The weight display value of the object to be measured is calculated based on the temperature measurement value measured by the temperature measurement means.

Further, the storage means in the weight measuring device of the present invention further stores a weight measurement value in an unloaded state measured by the weight measurement means in each of the plurality of temperature measurement values, and the weight measurement value is adjusted when the instrument difference is adjusted. The weight measurement values measured in the no-load state corresponding to the _two temperature measurement values T ₁ and T ₂ are D _Z1 and D _Z2, and the weight measurement value measured in the no-load state with respect to the temperature measurement value T _M1 in use. was a _{D ZM1,} when the temperature correction coefficient in the unloaded state relative to the temperature measurements _{T M1, T M2} and _{T COEF3,} weight measurements _{D ZM1} measured in no-load conditions at a temperature measurement value _{T M1} in use ' and weight measurements _{D ZM2} under no load conditions at a temperature measurement value _{T M2} to be measured at the time of use, the following equation _{T COEF3 = (D Z2 / D} Z1 -1) / (T -T _{1),
D ZM1 '= D Z1 · {} 1+ (T M1 -T 1) · T COEF3}, and _{D ZM2 = (D ZM1 / D} ZM1') · D Z1 · {1+ (T M2 -T 1) · T COEF3}
It is calculated | required by.

The temperature measurement values T ₁ and T ₂ in the weight measuring device of the present invention are characterized in that they are values closest to and next to the temperature measurement values T _M1 and T _M2 .

  Further, the calculation means in the weight measuring device of the present invention, the weight measurement value of the test body estimated by the calculation means in the temperature measurement value when measuring the test body, and when measuring the test body If the weight measurement value of the test specimen by the weight measurement means in the temperature measurement value is different, the test specimen having a known weight value measured by the weight measurement means in each of the plurality of temperature measurement values. Gravity correction is performed on the weight measurement value.

When the estimated weight measurement value of the specimen in the weight measuring device of the present invention is D _C ′, and the weight measurement value of the specimen measured by the weight measurement means is D _C , the calculation means The weight measurement value of a test body having a known weight measured by the weight measurement means in each of a plurality of temperature measurement values is multiplied by D _C / D _C ′.

  According to the present invention, the relationship between the temperature information and the weight value when the temperature is detected by the temperature sensor can be stored, and the weight can be corrected based on the relationship. The frequency of performing instrumental error adjustment by the person can be reduced, and convenience can be improved.

It is a block diagram which shows the control system of the weight measuring apparatus which concerns on embodiment. It is a figure which shows the flow of the instrument difference adjustment performed before factory shipment. It is a figure which shows the flow of the instrumental difference adjustment performed when a user uses. It is a graph which shows the relationship between the weight measurement value (AD conversion output value) in various temperature measurement values, and a weight display value. It is a graph which shows the relationship between a span coefficient and a temperature output value. It is a graph which shows the relationship between the weight measurement value (AD conversion output value) in a zero point, and a temperature output value. It is a graph which shows the relationship between the weight measurement value (AD conversion output value) in various temperature output values and weight display value for demonstrating gravity correction.

  Hereinafter, embodiments of a weight measuring device according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a control system of the weight measuring apparatus according to the embodiment.

The weight measuring device 1 mainly includes a weight sensor 3 that is a weight measuring unit that measures the weight of a measurement target, a temperature sensor 5 that is a temperature measuring unit for measuring the temperature of the weight sensor 3, and the temperature sensor 5. measuring a plurality of different temperature measurements which are _{(T C, T UC1, T} UC2 ···), and weight measurements of the specimen having a known weight measured by the weight sensor 3 at each of the temperature measurement And a storage unit 7 for storing adjustment factors (A _C , A _UC1 , A _UC2 ...) Indicating a relationship with the known weight of the test body, and the object to be generated that may be caused by a change in environmental temperature. And a calculation unit 9 that is a calculation unit that corrects a temperature error of a weight measurement value to be measured and calculates a weight adjustment value.
The calculation unit 9 is stored in the storage unit 7, the weight measurement value of the measurement target measured by the weight sensor 3, the temperature measurement value measured by the temperature sensor 5 in relation to the measurement of the measurement target. Various calculations are performed using the temperature measurement values (T _C , T _UC1 , T _UC2 ...) And the corresponding adjustment coefficients (A _C , A _UC1 , A _UC2 ...).

Furthermore, the weight measuring device 1 includes an AD conversion unit 11 for AD (analog-digital) conversion of the weight output value from the weight sensor 3 and the temperature output value from the temperature sensor 5 into a weight measurement value and a temperature measurement value, respectively. A display unit 13 for displaying a weight display value W calculated by the calculation unit 9 on the weight measurement value of the measurement target.
Each component of the weight measuring apparatus 1 is controlled by a microcomputer that is a control unit 15 having a storage unit 7 and a calculation unit 9. The storage unit 7 includes a ROM (non-volatile memory (Read Only Memory)), a RAM (volatile memory (Random Access Memory)), and the like.
The AD conversion unit 11 includes an AD converter 17 that performs AD conversion, and a switching unit 16 that switches input of the weight output from the weight sensor 3 and the temperature output from the temperature sensor 5 to the AD converter 17. Switching of the input to the AD converter 17 of the switching unit 16 is controlled by the control unit 15.
Further, the control unit 15 controls the display unit 13 to display information such as a weight display value and a temperature measurement value from the calculation unit 9. The display unit 13 can be a liquid crystal such as a full dot LCD (Liquid Crystal Display).
The weight measuring device 1 operates by being supplied with electric power from a power source (not shown) such as a battery or an external power source.

  The weight sensor 3 is connected to a mounting portion (not shown) on which a measurement target is placed, and when it receives a load from the measurement target, the weight sensor 3 is formed of a metal member having a strain generation portion that is deformed according to the load. The load cell includes a body and a strain gauge that is attached to the strain generating portion and whose output value changes according to deformation (stretching) of the strain generating portion. A full bridge circuit or a half bridge circuit is configured by the strain gauge. A weight detection circuit.

The temperature sensor 5 may be a member whose voltage or current changes according to the temperature change of the weight sensor 3, and for example, a thermistor, a temperature sensitive resistor, a diode, a pyroelectric temperature sensor, or the like can be used. In this embodiment, the temperature sensor 5 is provided only for measuring the temperature of the weight sensor 3. However, when an AD conversion IC incorporating the temperature sensor is used, the temperature of the weight sensor 3 is measured. This is preferable because it is not necessary to provide only a temperature sensor, and the configuration of the weight measuring apparatus 1 can be simplified.
Further, in the present embodiment, the temperature sensor 5 is directly fixed to the weight sensor 3, the temperature of the weight sensor 3 is measured, and the adjustment coefficient corresponding to the temperature measurement value is used. Is not limited to the weight sensor 3. For example, the weight sensor 3 and the temperature sensor 5 are separated from each other, and the temperature sensor 5 is used to measure the ambient temperature (air temperature) where the weight measuring device 1 is placed, or the configuration other than the weight sensor 3 that reflects the ambient temperature. It is good also as what is set as the structure which measures the temperature of a member and uses the adjustment coefficient corresponding to these temperature measurement values.

  A weight measuring apparatus according to the first embodiment will be described with reference to FIGS. In the first embodiment, a weight measuring apparatus that performs instrument difference adjustment using a span coefficient as an adjustment coefficient will be described. FIG. 2 is a diagram showing a flow of instrumental error adjustment performed before factory shipment, FIG. 3 is a diagram showing a flow of instrumental error adjustment performed when the user uses, and FIG. 4 is a weight at various temperature measurement values. FIG. 5 is a graph showing the relationship between the measured value (AD conversion output value) and the weight display value, and FIG. 5 is a graph showing the relationship between the span coefficient and the temperature output value.

  Throughout Example 1 and other embodiments described later, the instrumental difference means a value obtained by subtracting the true value of mass from the display value of the weight measuring apparatus, and the instrumental difference adjustment has a known weight by the weight measuring apparatus 1. It means that the weight measurement value of the test specimen is measured and the weight display value displayed on the display unit 13 (see FIG. 1) of the weight measuring apparatus 1 is adjusted to be the weight of the test specimen (JIS B- 7611-2: 2005).

  The initial instrument difference adjustment of the weight measuring device 1 performed at the factory before shipment is performed as shown in FIG. First, the zero point setting of the weight measuring device 1 is performed (step S1). Zero point setting refers to obtaining a weight output value (so-called zero point) from the load cell when no load is applied to the weight measuring device 1, and when the load is not applied, the weight display value is set to 0 on the display unit 13. (Zero) is displayed.

Next, the weight value of the test body having the known weight value W _C1 is measured by the weight measuring device 1 (step S2). Then, the weight output value from the weight sensor 3 is digitally converted by the AD conversion unit 11, and the weight measurement value _DC1 as a digital value is acquired and stored in the storage unit 7 (step S3). Furthermore, digitally converting the temperature output value from the temperature sensor 5 in the AD conversion unit 11, is stored in the storage unit 7 acquires the temperature measurement T _C as a digital value (step S4). Where it is stored in association to the measured temperature value T _C and weight measurements D _C1.

Finally, the adjustment coefficient _AC is calculated by the calculation unit 9 and stored in the storage unit 7 in association with the temperature measurement value T _C (step S5). Here, the adjustment coefficient _AC is a coefficient representing the relationship between the weight measurement value and the weight display value at a certain temperature measurement value. For example, in the case of a weight measuring apparatus capable of measuring up to 100 g, when the temperature measurement value is T _C and the adjustment coefficient when a test body having a mass of 100 g is placed is A _C , A _C · D _C1 = 100 A coefficient A _C (in this case, a span correction coefficient) is obtained. Adjustment coefficient A _C is used to derive the weight display from the weight measurements of the object to be measured.

  Furthermore, before using the weight measuring apparatus 1 (before starting measurement), the instrumental difference adjustment (user adjustment) performed by the user is performed as shown in FIG. First, when an operation for adjusting the instrumental difference is started by the user in a certain environment (first environment), the weight measuring device 1 has been described in relation to the instrumental error adjustment (step S1) before factory shipment in FIG. The zero point is set in the same manner as in (Step S11).

Next, the weight of the test body having the known weight value W _C1 is measured by the weight measuring device 1 (step S12). Further, the temperature output value from the temperature sensor 5 is acquired as the temperature measurement value _TUC1 digitally converted by the AD conversion unit 11 (step S13). Then, the calculation unit 9 determines whether or not the storage unit 7 has a storage capacity capable of storing the temperature measurement value _TUC1 (step S14). In step S14, when it is determined that there is a storage capacity capable of storing the temperature measurement value T _UC1 (No in step S14), the temperature measurement value T _UC1 acquired previously is stored in the storage unit 7 (step S15). The process proceeds to step S17.
If it is determined in step S14 that the storage unit 7 does not have a storage capacity capable of storing the temperature measurement value _TUC1 (Yes in step S14), the temperature acquired this time from the stored temperature measurement values The temperature measurement value closest to the measurement value T _UC1 and the weight measurement value and adjustment coefficient associated with the temperature measurement value are deleted (step S16), and the temperature measurement value T _UC1 acquired this time is stored in the storage unit 7. (Step S15), and the process proceeds to the next step S17.
The weight output value from the weight sensor 3 is digitally converted by the AD conversion unit 11, and the weight measurement value _DUC1 as a digital value is acquired and stored in the storage unit 7 (step S17). Here, the temperature measurement value T _UC1 and the weight measurement value D _UC1 are stored in association with each other.

Finally, the adjustment coefficient A _UC1 is obtained by calculation by the calculation unit 9 and stored in the storage unit 7 (step S18). As described with reference to FIG. 2, the adjustment coefficient is a coefficient representing the relationship between the weight measurement value and the weight display value at a certain temperature measurement value, and the weight display value is derived from the weight measurement value of the measurement target. Used for. The adjustment coefficient A _UC1 is stored in association with the temperature measurement value T _UC1 .

In the environment (second environment) different from the temperature measurement value _TUC1 , when the user starts the adjustment of the instrumental error, the weight measurement device 1 follows the steps S11 to S18 in FIG. and T _UC2, the weight measurement value _{D UC2} in temperature measurements _{T UC2,} and the adjustment coefficients _{a UC2,} the acquisition and save, instrumental error adjustment is carried out. The number of temperature measurement values, weight measurement values, and adjustment coefficients to be stored in the storage unit 7 may be determined at the time of shipment according to the size of the storage capacity of the storage unit 7 or set arbitrarily by the user. It may be made possible and is not particularly limited. In step S16 of this embodiment, the temperature measurement value closest to the temperature measurement value acquired this time and the data related thereto are deleted from the temperature measurement values already stored. It is also possible to adopt a configuration in which the oldest data is deleted from the acquired data, and there is no particular limitation.

Next, a process for obtaining an adjustment coefficient in instrument difference adjustment will be described. With reference to FIG. 4 and FIG. 5, a case will be described in which data for performing instrument difference adjustment is acquired once before factory shipment and twice before being used by the user. In FIG. 4, the horizontal axis indicates the weight measurement value after AD conversion, and the vertical axis indicates the weight display value. A line indicated by _TC indicates a known weight value W _C1 and a weight in a temperature measurement value T _C (or an actual temperature converted from the temperature measurement value, the same applies hereinafter) when an operation for adjusting the instrumental error is performed. The relationship with measured value _DC1 is shown. _Similarly, the line indicated by T _{UC1, T UC2} shows the relationship between the known weight value _{W C1} and weight measurements _{D UC1, D UC2} at each temperature output value _{T UC1, T UC2.} Line indicated by T _M indicates the relationship between the weight display and weight measurements in the temperature output value T _M.

In FIG. 5, the horizontal axis indicates the AD-converted temperature measurement value, and the vertical axis indicates the span coefficient that is an adjustment coefficient. The span coefficient is the slope of each line in the graph of FIG. For example, the span coefficient S _C when the temperature measurement value is T _C is expressed as S _C = W _C1 / D _C1 .

As shown in FIG. 5, when plotting the span coefficients S _C , S _UC1 , S _UC2 at each temperature measurement value T _C , T _UC1 , T _UC2 , an approximate line F showing the relationship between the temperature measurement value and the span coefficient. Is obtained, and a first-order approximate expression can be obtained. Specifically, it is represented by the following formula.
S _M = S _C + (S _UC2 −S _C ) · (T _M −T _C ) / (T _UC2 −T _C ) (1)

In the above equation (1), the temperature measurement values T _C and T _UC2 and the corresponding span coefficients S _C and S _UC2 are selected, and the temperature measurement value T _{M of the} environment where the weight measurement device 1 is actually placed is selected. seeking span coefficient S _M in. To increase the accuracy of the instrumental error adjustment, and selection and the closest temperature measurements T _C to a temperature measurement value under the current environment, a temperature measurement T _UC2 close next. Thus, if, for the temperature measurement under the current environment, if the measured temperature close to the second is the _{T UC1} rather than _{T UC2} replaces the _{T UC2} in (1) to _{T UC1} span it may be obtained the coefficient _{S M.}

  For example, the temperature measurement value when the instrumental difference adjustment is performed at the factory before shipment is 25 ° C. (first environment), and then the instrumental difference adjustment is performed three times by the user. Are 10 ° C. (second environment), 20 ° C. (third environment), and 30 ° C. (fourth environment), and each data is already stored in the storage unit 7. Thereafter, when the user uses the weight measuring device 1 to measure the weight of an object to be measured, and the temperature measurement value at the time of measurement is 13 ° C., the temperature measurement value in the current environment Using the closest measured temperature value of 10 ° C. to (13 ° C.), the next closest measured temperature value of 20 ° C., and the measured weight value and span coefficient corresponding to these measured temperature values, the measured temperature value at 13 ° C. Find the span coefficient.

In this way, the span coefficient S _M at the temperature measurement value T _M in the current environment is obtained. Then, the following equation can be obtained weight display W _M to be measured.
W _M = D _M · S _M (2)

Also it shows a line indicating the relationship between W _M and D _M at the temperature measurements T _M in FIG. 4 for reference. According to this embodiment, as the number of times the user performs instrumental error adjustment increases, the number of data on the relationship between the temperature measurement value and the span coefficient can be saved, and the instrumental error of the weight measuring device 1 can be saved. Adjustment accuracy can be improved.

  In Example 1 described above, the temperature measurement value is acquired after the weight measurement value is acquired, but the present invention is not particularly limited to this order. In other words, if the temperature of the weight sensor when acquiring the weight measurement value is the same as the temperature of the weight sensor when acquiring the temperature measurement value, the timing for acquiring the weight measurement value and the timing for acquiring the temperature measurement value Can be changed as appropriate.

  Further, in the above example and the examples described later, in order to adjust the instrumental difference, the data is acquired three times using the test specimen. However, when the temperature measurement values are different, the data is acquired at least twice. Thus, the instrumental error can be adjusted, and the object of the present invention of correcting the temperature error can be achieved.

  Next, a weight measuring apparatus according to a second embodiment, which uses a span coefficient as an adjustment coefficient, but performs instrumental difference adjustment that is different from the first embodiment in how to derive the span coefficient, will be described with reference to FIG. In the first embodiment, the relationship between the temperature measurement value and the span coefficient is stored. In the present embodiment, the temperature correction coefficient for the span coefficient is stored.

Based on the span coefficient _{S C} at the temperature measurement value _{T C,} the temperature correction coefficient _{T coef1} in the temperature measurements _{T UCN} is given by: and is stored in the storage unit 7.
T _COEF1 = (S _UCN / S _C -1) / (T _UCN -T _C ) (3)
N is to take the point closest to T _M on the accuracy preferred. Therefore, according to FIG. 5, for T _M , T _UC2 is closer to T _UC1 and the closest point is N = ₂ from T _UC2 . Therefore, the above equation (3) is
_{T COEF1 = (S UC2 / S} C -1) / (T UC2 -T C)
It becomes. The temperature correction coefficient T _COEF1 represents the slope of the line F shown in FIG.

Furthermore, the span coefficient S _M at the temperature measurement value T _M when the weight measuring apparatus 1 is used is obtained by a first-order approximation formula as the simplest example, and is stored in the storage unit 7.
S _M = S _C · {1+ (T _M −T _C ) · T _COEF1 } (4)
By substituting previously obtained T _COEF1 into this equation (4), S _M can be obtained.

The above formula (3), (4), the term of the temperature measurements T _C used during instrumental error adjustment using the value closest to the measured temperature value T _M of the measurement of the object to be measured, the temperature measurement value T the term _UCN, to use a value close to the temperature measurement value T _M in the following, preferable in increasing the accuracy of the instrumental error adjustment. After obtaining the span coefficient S _M by the equation (4), the weight display value W _M can be obtained by the equation (2) described in the first embodiment.

Next, a weight measuring apparatus according to a third embodiment, which uses a span coefficient as an adjustment coefficient, and performs instrument difference adjustment that differs from the first and second embodiments in how to derive the span coefficient, will be described. The third embodiment is configured to store the temperature correction coefficient for the weight measurement value after AD conversion at the time of instrument difference adjustment.
Referring to FIG. 4, the weight measurement values D _C1 and D _UCN after AD conversion at the temperatures T _C and T _UCN (in FIG. 4, T _UC1 or T _UC2 ) at the time of each adjustment (in FIG. 4, D _UC1 or D _UC2 ), the temperature correction coefficient T _COEF2 at the temperature T _UCN based on the temperature measurement value T _C is obtained by the equation (5) and stored in the storage unit 7.
_{T COEF2 = (D UCN / D} C1 -1) / (T UCN -T C) ··· (5)
N is to take the point closest to T _M on the accuracy preferred. Therefore, according to FIG. 5, for T _M , T _UC2 is closer to T _UC1 and the closest point is N = ₂ from T _UC2 . Therefore, the above equation (5) is as follows.
T _COEF2 = (D _UC2 / D _C1 −1) / (T _UC2 −T _C )

The weight measurement value D _M ′ after AD conversion estimated for the known weight value W _C1 in the temperature measurement value T _M acquired when the weight measurement apparatus 1 is used is approximated by a linear expression as the simplest example. When it is performed, it is obtained by the equation (6).
D _M ′ = D _C1 + (D _UCN −D _C1 ) · (T _M −T _C ) / (T _UCN −T _C ), or
D _M ′ = D _C1 · {1+ (T _M −T _C ) · T _COEF2 } (6)
Then, D _M ′ can be obtained by substituting the previously obtained T _COEF2 into Equation (6).

Equation (5), in (6), the term of the temperature measurements T _C used during instrumental error adjustment using the value closest to the measured temperature value T _M of the measurement of the object to be measured, the temperature measurements T _UCN the sections to use a value close to the temperature measurement value T _M in the following, preferable in increasing the accuracy of the instrumental error adjustment. Further, the span coefficient S _M in the weight measurement value D _M ′ has the relationship of Expression (7).
S _M = W _C1 / D _M ′ (7)
Furthermore, the weight measurement value _{D M} after AD conversion, and span coefficient _{S M} obtained by the equation (7), the equation (8) for multiplying a guided weight display value _{W M.}
W _M = D _M · S _M (8)

  Next, a weight measuring apparatus according to a fourth embodiment that performs instrumental difference adjustment for zero point setting will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the weight measurement value (AD conversion output value) at the zero point and the temperature output value.

  The instrumental difference adjustment in the fourth embodiment is a configuration in which the weight measurement values after AD conversion when acquiring the zero point in the zero point setting are acquired and stored for a plurality of temperature measurement values. That is, in this embodiment, the influence of the temperature of the weight measurement value at the zero point is taken into consideration. The weight measurement value at the zero point in the no-load state may fluctuate due to the temperature change of the environment and may cause an offset error. Therefore, in this embodiment, the offset error due to the temperature change is corrected.

As shown by the line A in FIG. 6, using the relationship between the weight measurement value after AD conversion in the temperature measurement value and zero point, it is approximated by a linear equation, temperature correction for a no-load state temperature measurements T _C as a reference The coefficient T _COEF3 is obtained by Expression (9).
_{T COEF3 = (D ZUCN / D} ZC -1) / (T UCN -T C) ··· (9)
Moreover, the are stored in the weight measurement value D _ZM1 is obtained storage unit 7 after AD conversion of zero point when the temperature measurements T _M1, and temperature measurements T _M1 during measurement of the object to be measured . In this case, the weight measurement value D _ZM1 ′ after AD conversion estimated with respect to the zero point in consideration of the temperature change at the time of instrument difference adjustment in the temperature measurement value T _M1 is obtained by Expression (10).
_{D ZM1 '= D ZC · {} 1+ (T M1 -T C) · T COEF3} ··· (10)
Further, when the temperature measurement value when the measurement target is measured is T _M2 , the zero-point weight measurement value D _ZM2 is obtained by Expression (11).
_{D ZM2 = (D ZM1 / D} ZM1 ') · D ZC · {1+ (T M2 -T C) · T COEF3} ··· (11)

Here, the term of the temperature measurement value T _{C and} the term of the temperature measurement value T _UC2 at the time of zero point setting by the user are the values closest to the temperature measurement values T _M1 and T _M2 at the time of measurement of the measurement target, and the next It is preferable to set the variable N so as to be a value close to that in order to improve the accuracy of the instrumental error adjustment. By using the weight measurement value D _ZM2 at the zero point obtained by the equation (11), the accuracy of the instrumental error adjustment described in the first to third embodiments can be further increased, and as a result, the weight display value W _M can be obtained with high accuracy. Can be obtained.

  In the calculation formula of Example 4 above, the temperature measurement value obtained for instrumental error adjustment before factory shipment, the weight measurement value at the zero point after AD conversion, and the instrumental error adjustment value obtained before use by the user. The zero used when measuring the measured object between the measured temperature value closest to the measured temperature value at the time of measuring the measured object and the zero point weight measured value after AD conversion. The point weight measurement is calculated.

  However, if the user has acquired the temperature measurement value closest to the temperature measurement value at the time of measurement and the next closest temperature measurement value for adjustment of the instrument difference, The zero point weight measurement value after AD conversion may be calculated at the time of measurement using the zero point weight measurement value. For example, if the temperature measurement value at the time of instrumental error adjustment at the factory is 25 ° C, and the temperature measurement value at the time of instrumental error adjustment by the user is 10 ° C, 20 ° C, 30 ° C, the zero point weight measurement value When the temperature measurement value at the time of measurement is 15 ° C., the temperature measurement value 10 ° C. and 20 ° C. and the zero point weight measurement value after AD conversion in this temperature measurement value should be used to set the zero point with high accuracy. Can do.

  In the first to fourth embodiments, the temperature measurement value, the weight adjustment value, and the zero point adjustment coefficient at the time of instrument difference adjustment are not stored in the factory, or the instrument difference adjustment at the factory or when the instrument difference adjustment is performed by the user. Even if the measured temperature value, zero point adjustment coefficient, etc. are accidentally erased during use, the user performs instrumental error adjustment and accumulates the temperature measurement value and adjustment coefficient, resulting in a weight error due to temperature. It is possible to realize a weight measuring device capable of correcting the above.

  Furthermore, in the first to fourth embodiments, after the data for adjusting the instrumental error at the time of shipment from the factory is acquired, the information for adjusting the instrumental error is acquired by the user. Acquisition of information for adjusting instrument differences in at least two different temperature measurement values, such as upper and lower temperature measurement values of the temperature range used, or temperature measurement values between the upper (lower) temperature measurement value and the temperature range It is good also as a structure which performs information and preserve | saves information required for instrument difference adjustment. With this configuration, it is possible to obtain a measurement result whose temperature is corrected from the start of use by the user, that is, a weight display value, without the user adjusting the instrumental error of the weight measuring device 1.

  A weight measuring apparatus according to a fifth embodiment that performs gravity correction will be described with reference to FIG. Conventionally, for gravity errors of weight measurement values due to changes in the use area of the weight measurement device, the user can make initial settings related to gravity and the gravity setting region setting mode built into the device. This is dealt with by setting the area of use. There is also known a method in which gravitational acceleration sensor provided in the weight measuring device acquires gravitational acceleration during use and automatically performs gravity correction.

According to the weight measuring apparatus of the fifth embodiment, the measurement error caused by the gravitational difference can be corrected by using the weight measurement values, the span coefficients, etc. of the plurality of temperature measurement values used in the first to fourth embodiments. First, a T _C is the temperature measurements to obtain for instrumental error adjustment before shipment at the point A, the weight measurements of the specimen after the AD conversion is D _C. Here, the temperature measurement value acquired for the first instrument difference adjustment before use is T _UC1 , and the weight measurement value of the specimen after AD conversion is D _UC1 . And it moves to the point B different from the point A, the temperature measurement value acquired for the instrument difference adjustment of the 2nd time before use is _TUC2 , and the weight measurement value of the test body after AD conversion is _DUC2 .

When the temperature measurement value T _UC2 at the point A, the weight measurement value after AD conversion estimated by the calculation unit is set to D _UC2 ′. Here, the weight measurement value _{D UC2} in temperature measurements _{T UC2} ', by using the temperature measurements _{T C} and weight measurements _{D C,} and a temperature measurement value _{T UC1} and weight measurements _{D UC1,} 2, As described in connection with 3, the weight measurement D _UC2 ′ is obtained.

Next, the weight measurement value _DUC2 of the test specimen is measured by the weight measuring means. Here, when the previously estimated weight measurement value D _UC2 ′ is different from the weight measurement value D _UC2 , the calculation unit 9 determines that a gravity change has occurred.
In this case, in order to gravity-correct the weight measurement values D _C and D _UC1 stored in the storage unit 7, the gravity measurement coefficient D _UC2 / D _UC2 ′ is calculated on the weight measurement values D _C and D _UC1. The weight measurement value multiplied by the unit 9 and subjected to gravity correction is stored in the storage unit 7 in association with each temperature measurement value. Thereafter, the instrumental difference adjustment process is performed in the same manner as in Examples 1 to 5, and the weight measuring device 1 is ready to measure the weight of the measurement target.

On the contrary, when the weight measurement value D _UC2 ′ and the weight measurement value D _UC2 are the same, it is determined by the calculation unit 9 that there is no gravity change, and gravity correction is not performed. Thereafter, the weight of the measurement target is measured using the information on the instrumental difference adjustment already stored in the storage unit 7. Thus, according to the present embodiment, even if the place of use of the weight measuring apparatus 1 moves, the weight can be accurately measured without being affected by the gravity change.

  In the gravity correction, as in the first to fifth embodiments, information for adjusting the instrumental difference is acquired at least at two different temperature measurement values, and the temperature measurement value and the weight measurement value necessary for the instrumental difference adjustment are obtained. It must be stored in the storage unit 7. Further, by increasing the number of times of acquiring information for adjusting the instrumental difference, information on the temperature measurement value close to the temperature measurement value when measuring the measurement target can be obtained, and the accuracy of gravity correction can be improved.

  In the calculation formulas of Examples 1 to 5, the temperature measurement value, the span coefficient, and the weight measurement value for instrumental error adjustment acquired at the time of shipment from the factory and the detection for instrumental error adjustment acquired by the user. Of the measured temperature value, span coefficient, and weight value measured, the measured temperature value close to the measured temperature value when actually measuring the measurement target (zero point), the measured temperature value related to the measured temperature value, and the span Between the coefficient, the weight measurement value after AD conversion at the time of measurement, and the span coefficient are calculated.

  However, if the temperature measurement value obtained when measuring the weight of the object to be measured has the value closest to the temperature measurement value obtained when adjusting the user's instrumental error, and the next closest value, the weight measurement is performed. If the weight and the weight value after AD conversion at the time of measurement are calculated based on the value and the span coefficient, a weight display value with high accuracy can be obtained. For example, when the temperature measurement value acquired at the time of instrument difference adjustment before factory shipment is 25 ° C and the temperature measurement value acquired at the time of instrument difference adjustment by the user is 10 ° C, 20 ° C, 30 ° C, When the temperature measurement value is 15 ° C., the weight measurement value after AD conversion at 10 ° C. and 20 ° C., the span coefficient, etc. are used. Corresponds to the temperature measurement value obtained when measuring the weight of the object to be measured, the closest value to the temperature measurement value obtained for instrumental error adjustment, the next closest value, and the temperature measurement value obtained for instrumental error adjustment. It is preferable to use the weight measurement value to be measured and the span coefficient to calculate between the weight measurement value after AD conversion at the time of measurement of the measurement target and the span coefficient, because a weight display value with high accuracy can be obtained.

  The present invention can be embodied in many forms without departing from its essential characteristics. Therefore, it is needless to say that the above-described embodiments and examples are merely illustrative and do not limit the present invention.

  The weight measuring device according to the present invention is particularly applicable to a device that measures the weight of a measurement object that is relatively light, for example, a cooking scale for weighing food at home.

DESCRIPTION OF SYMBOLS 1 Weight measuring device 3 Weight sensor 5 Temperature sensor 7 Memory | storage part 9 Calculation part 11 AD conversion part 13 Display part 15 Control part 16 Switching part 17 AD converter

Claims (7)

A weight measuring means for measuring a weight value of an object to be measured;
Temperature measuring means for measuring the temperature of the weight measuring means or the ambient temperature of the weight measuring means ;
A plurality of temperature measurement values measured by the temperature measurement means, a weight measurement value of a specimen having a known weight value measured by the weight measurement means in each of the plurality of temperature measurement values, a known value of the test specimen Storage means for storing an adjustment coefficient indicating a relationship with the weight value;
A calculation means for correcting a temperature error of the weight measurement value of the measurement target and calculating a weight adjustment value,
The calculation means includes a weight measurement value of the measurement target measured by the weight measurement means, a temperature measurement value measured by the temperature measurement means in relation to the measurement of the measurement target, and the storage means Using the stored temperature measurement and the corresponding adjustment factor,
The adjustment coefficient is a span coefficient representing a relationship between the weight measurement value and the weight adjustment value in the measured temperature measurement value, and two temperature measurement values arbitrarily selected from the plurality of temperature measurement values are represented by T ₁ , T ₂ , S ₁ and S ₂ are the span coefficients corresponding to the _two temperature measurement values T ₁ and T ₂ , D _{M is} the measured weight measurement value of the measurement target, and the measured temperature of the measurement target When the measured value is T _M , the span coefficient S _M and the adjusted weight adjustment value W _M corresponding to the temperature measured value T _M are expressed by the following formulas S _M = S ₁ + (S ₂ −S ₁ ) · (T _M− T ₁ ) / (T ₂ −T ₁ ), and W _M = D _M · S _M
A weight measuring device obtained by _2. The weight measuring device according to claim 1, wherein the temperature measurement values T ₁ and T ₂ are values closest to and next to the temperature measurement value T _M.   The computing means is measured by the temperature measuring means in relation to a weight measurement value measured by the weight measurement means in an unloaded state and a weight measurement value measured by the weight measuring means in the no-load state. The weight measuring device according to claim 1 or 2, wherein a weight display value of the object to be measured is calculated based on a temperature measurement value. The storage means further stores a weight measurement value in an unloaded state measured by the weight measurement means in each of the plurality of temperature measurement values, and the two temperature measurement values T ₁ , T when adjusting the instrumental error. _The weight measurement values measured in the no-load state corresponding to ₂ are D _Z1 and D _Z2 , the weight measurement value measured in the no-load state with respect to the temperature measurement value T _M1 in use is D _ZM1 , and the temperature measurement value T _{If the} temperature correction coefficient in the no-load state for _M1 and T _M2 is T _COEF3 , the weight measurement value D _ZM1 ′ measured in the no-load state at the temperature measurement value T _M1 in use and the temperature measurement measured in the use The weight measurement value D _ZM2 in the no-load state at the value T _M2 is given by the following formula: T _COEF3 = (D _Z2 / D _Z1 −1) / (T ₂ −T ₁ ),
_{D ZM1 '= D Z1 · {} 1+ (T M1 -T 1) · T COEF3}, and _{D ZM2 = (D ZM1 / D} ZM1') · D Z1 · {1+ (T M2 -T 1) · T COEF3}
The weight measuring device according to claim 3, wherein the weight measuring device is obtained by: 5. The weight measuring apparatus according to claim 4, wherein the temperature measurement values T ₁ and T ₂ are values closest to and next to the temperature measurement values T _M1 and T _M2 .   The calculation means is based on the weight measurement value of the test specimen estimated by the calculation means in the temperature measurement value when measuring the specimen, and the weight measurement means in the temperature measurement value when measuring the specimen. If the weight measurement value of the test specimen is different, gravity correction is performed on the weight measurement value of the test specimen having a known weight value measured by the weight measurement means in each of the plurality of temperature measurement values. The weight measuring device according to any one of claims 1 to 5, wherein Assuming that the estimated weight measurement value of the test specimen is D _C ′, and the weight measurement value of the test specimen measured by the weight measurement means is D _C , the calculation means is configured to each of the plurality of temperature measurement values. 7. The weight measuring apparatus according to claim 6, wherein a weight measurement value of a test body having a known weight measured by the weight measuring means is multiplied by D _C / D _C ′.

Images