JPH0658237B2 - Reference point correction device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference point correction device for a measuring device for measuring various quantities such as weight, flow rate and length.

[0002]

2. Description of the Related Art In a measuring apparatus for measuring weight, flow rate, length and the like with high accuracy, a reference point (for example, a zero point) often changes with the passage of time, which often causes deterioration of measurement accuracy.

For this reason, conventionally, as shown in FIG. 4, a zero point is measured every fixed number of times, the reference point is updated and stored in the zero point storage circuit 1, and the measurement signal (measurement signal) of the measuring device (for example, scale) 2 is measured. ) Is subtracted by the subtraction circuit 3.

[0004]

However, in this method,
As shown in FIG. 5, when the zero point changes with the number of times of measurement, if the zero point is measured and updated and stored in the zero point memory circuit 1 at the number of times of measurement B ₁ and B ₂ times, B ₁ times, B ₂
At the number of times of measurement B ′ in the middle of the times, the error E ′
Occurs, and an error E ″ occurs in the number of measurements B ″ after B ₂ times.

Therefore, in order to reduce such an error,
The zero point must be measured and updated and stored for every few measurement times. Therefore, in a measuring device that continuously measures a large number of objects to be measured at high speed, continuous supply of the objects to be measured is often interrupted for zero point measurement, which hinders high-speed measurement.

When the change in the zero point is not linear as shown in FIG. 5 but changes in a quadratic curve, it is necessary to correct the zero point corresponding to the change in the quadratic curve.

The present invention solves the above-mentioned problems, the measurement of the reference point does not need to be performed as described above, and an error hardly occurs in response to a quadratic curve change. It is an object of the present invention to provide a reference point correction device.

[0008]

In order to achieve the above-mentioned object, a reference point correction apparatus according to the present invention comprises a measuring device for measuring an object to be measured and outputting a measurement value, and a measuring device for measuring the object to be measured. A reference value storage circuit that stores a constant load measurement value, a first constant load measurement value during the first constant load measurement stored in the reference value storage circuit, and a second constant load state that is measured thereafter. A first subtraction circuit that calculates a difference from a second constant load measurement value from the measuring device, and a difference between the first and second constant load measurement values output from the first subtraction circuit are A first division circuit that divides by a measurement frequency difference value between the first and second constant load measurements; a reference value change degree storage circuit that stores an output value of the first division circuit; and a reference value change degree By the first reference value change degree stored in the storage circuit, and then the second and third constant load measurements. And a second reference value output from the second subtraction circuit, the second subtraction circuit calculating a difference from the second reference value change degree output from the first division circuit. A second division circuit that divides the difference in the degree of change by the difference in the number of times between the second and third constant load measurements, and a degree-of-change memory circuit that stores the output value of the second divider circuit. A first multiplication circuit that multiplies the reference value change degree stored in the reference value change degree storage circuit by the number of times difference between the current measurement time and the third constant load measurement time; A second multiplication circuit that multiplies the degree of change of the reference value change stored in the degree-of-change storage circuit by the square of the number of times difference between the current measurement time and the third constant load measurement time; The output value of the multiplying circuit and the output value of the second multiplying circuit are stored in the reference value storage circuit as the third constant value. And a third subtraction circuit for correcting the reference value by subtracting the output value of the addition circuit from the measurement value at the current measurement. I am trying.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. For convenience of explanation, it is assumed that the measured value when measured in the constant load state corresponds to the reference point, and the measured value when measured in the no-load state corresponds to the zero point. To do.

FIG. 1 is a block diagram showing an embodiment of the present invention applied to a weighing device.

In FIG. 1, 11 is a weighing pan for placing an object to be measured, 12 is a weighing instrument, 13 is a zero point of the weighing instrument 12 when the weighing dish is emptied and the zero point is measured, and a zero point signal is stored. Is a zero-point hold circuit for holding. Reference numeral 14 is an old zero point storage circuit for storing the zero point signal held in the zero point holding circuit 13 when the switch 15 is closed, 16
Is a first subtraction circuit for subtracting the old zero point stored in the old zero point storage circuit 14 from the zero point held in the zero point hold circuit 13.

Reference numeral 17 is a counter for counting the number of times of measurement by the weighing device 12.

Reference numeral 19 denotes an old number storage circuit for storing the number of times of measurement counted by the counter 17 when the switch 20 is closed in synchronization with the switch 15.

Reference numeral 21 is a subtraction circuit for subtracting the old number stored in the old number storage circuit 19 from the number of measurements counted by the counter 17.

A reference numeral 22 divides the difference between the new zero point and the old zero point output from the first subtraction circuit 16 by the difference between the new number of times and the old number of times output from the subtraction circuit 21, and a zero point per time. It is a first division circuit for calculating the degree of change.

The switch 23 includes a switch 24 and switches 15 and 2
When 0 is closed before it is closed synchronously, the first
The zero point change degree storage circuit for storing the output signal (zero point change degree) of the division circuit 22, and the new number and the old number output from the subtraction circuit 21 to the zero point change degree output from the zero point change degree storage circuit 23. It is a multiplication circuit for multiplying the difference of.

Reference numeral 41 denotes the first zero point (reference value) change degree stored in the reference value change degree storage circuit 23 (that is, the number of measurements when the zero point changes in a quadratic curve as shown in FIG. 3, for example). The degree of change between B ₁ and the number of times of measurement B ₂ ) and the degree of change of the second zero point (reference value) output from the first division circuit by the second and third constant load measurements (FIG. 3). Is a second subtraction circuit for calculating the difference between the number of measurements B ₂ and the degree of change between the number of measurements B ₃ (that is, the difference between the slopes of the straight line PQ and the straight line QS).

Reference numeral 42 denotes the difference between the degrees of change of the first and second zero points (reference values) output from the second subtraction circuit 41.
The second, a second divider circuit for dividing by a third constant-load measurement (measuring the number B _3, B ₂₎ times difference between (B ₃ -B _2).

Reference numeral 44 is a change degree storage circuit for changing the zero point (reference value) which stores the output value of the second division circuit 42 via the switch 43.

Numeral 25 indicates the degree of change in the zero point (reference value) stored in the zero point (reference value) change storage circuit 23 between the current measurement number B ″ and the third constant load measurement number B ₃ (FIG. 3). It is a first multiplication circuit that multiplies the difference in the number of times).

Reference numeral 45 denotes the degree of change of the zero point (reference value) change stored in the degree of change of the zero point (reference value) change, and the current measurement number B ″ and the third constant load measurement number B ₃ It is the 2nd multiplication circuit which multiplies the square of the number of times between.

Reference numeral 26 denotes the third constant load measurement in which the output value of the first multiplication circuit 25 and the output value of the second multiplication circuit 45 are stored in the zero point (reference value) hold circuit 13. an addition circuit for adding the constant load measurements Z ₃ at times B _3.

Numeral 27 represents the measured value at the current measurement number B ″,
It is a third subtraction circuit that subtracts the output value of the addition circuit 26 to correct the zero point (reference value).

Reference numeral 28 is a display circuit for displaying the weight of the object to be measured based on the output signal of the third subtraction circuit 27.

The switches 15, 20, 24 and 43 are closed by timing signals T ₁ , T ₂ , T ₃ and T ₄ , respectively. FIG. 2 shows timing signals T ₁ , T ₂ , T ₃ , T ₄
3 and the timing signal T ₀ described later.

Next, the operation of the zero point correction according to the above embodiment will be described by taking the case where the zero point changes as shown in FIG. 3 as an example.

The zero point change degree is set in the zero point change degree storage circuit 23 as follows.

That is, as shown in FIG. 3, the weighing pan 11 is emptied at the number of times of measurement B ₁ , and the output value (zero point) Z ₁ of the weighing instrument 12 at this time is stored at the timing T ₀ shown in FIG. 2, for example. , The zero-point hold circuit 13 holds it. When the switches 15 and 20 are temporarily closed synchronously, the old zero point memory circuit 14 stores the zero point Z ₁ held by the zero point hold circuit 13, and the count value of the counter 17 at this time (measurement count). ) Is the old number memory circuit 1
9 is stored.

Next, after a lapse of a predetermined number of times, the weighing pan 11 is emptied again, and the output value (zero point) from the weighing device 12 is held in the zero point holding circuit 13.

As shown in FIG. 3, the number of measurements at this time is B
The output value of the meter 12 by ₂ when (zero point) is assumed to be Z _2, old zero point stored in the first subtraction circuit 16 from the zero point is held in the zero point holding circuit 13 Z ₂ the old zero point storage circuit 14 the difference Z ₂ -Z ₁ and Z ₁ are output, whereas the difference B ₂ -B ₁ and the number of measurements B ₂ by the counter 17 from the subtracting circuit 21 and the previously-measured number B ₁ is outputted, the first division circuit 22 calculates the _{(Z 2 -Z 1) / (} B 2 -B 1).

When the switch 24 is temporarily closed by the timing signal T ₃ , the output value of the division circuit 22 (Z ₂ -Z
₁ ) / (B ₂ −B ₁ ) is stored in the zero point change degree storage circuit 23.

Immediately after the timing signal T ₃ , the timing signals T ₁ and T ₂ are output, the switches 15 and 20 are synchronized and temporarily closed, and the zero point Z ₂ held by the zero point holding circuit 13 is the old zero point storage circuit. 14 is stored in place of Z _{1 and} the number of measurements B ₂ of the counter 17 is stored in the old number of measurements storage circuit 19 in place of B ₁ .

When the new zero point (Z ₂ ) is measured in this way, the (reference value) degree of change (Z ₂ −Z ₁ ) / (B ₂ −
B ₁ ) is set in the zero point change degree storage circuit 23.

This degree of change represents the slope of the straight line PQ connecting the zero points P and Q at the number of measurements B ₁ and B ₂ in FIG.

Next, as shown in FIG. 3, when the zero point Z ₃ is measured at the number of times of measurement B ₃ , the first division circuit 22 similarly performs the following zero point (reference value) degree of change (Z ₃ -Z). ₂ ) / (B
_3- B ₂ ) is output. This represents the slope of the straight line QS.

The difference between the degrees of change of the first and second zero point (reference value) changes is output from the second subtraction circuit, and this difference is the difference in the number of measurements B ₃ and B ₂ (B ₃ -B ₂ ) is divided by the second division circuit 42. This is the zero point (reference value)
The change degree of change is stored in the change degree storage circuit 44 of change of the zero point (reference value).

If the number of times of the subsequent measurement of the measured object becomes B ″ as shown in FIG. 3, the second zero point (reference value) change degree (Z ₃ − Z ₂ ) / (B ₃ −B ₂ ) is output and the counter 17 outputs the number of times B ″. Therefore, the subtraction circuit 21 outputs (B ″ −B ₃ ) to the first multiplication circuit 25. Therefore, the first multiplication circuit 25 outputs {(Z ₃ −
Z ₂ ) / (B ₃ −B ₂ )} × (B ″ −B ₃ ) is output.

As shown in FIG. 3, (Z ₃ -Z ₂ ) / (B ₃
-B ₂ ) represents the slope of the straight line connecting the Q point and the S point, so {(Z ₃ −Z ₂ ) / (B ₃ −B ₂ )} × (B ″
-B ₃ ) represents the length of the straight line RM that connects the intersection R of the extension of the straight line QS and the vertical line passing through B ″ and the intersection M of the horizontal line passing through S and the vertical line passing through B ″. There is.

At the time of the number of measurements B ″, the second multiplication circuit 45 determines the degree of change of the zero point (reference value) change (that is, the difference between the slope of the straight line QS and the slope of the straight line PQ by the number of times difference (B ₃ −
The value obtained by dividing the number of times (B ″ −B ₃ ) by 2 is multiplied by the value obtained by dividing by B ₂ ).

The degree of change of the change obtained by dividing the difference between the slopes of the straight line QS and the straight line PQ by the number of times difference (B ₃ -B ₂ ) is P, Q, S.
The quadratic curve passing through the three points is a straight line QS on the right side of the S point.
The degree of inclination is larger or smaller than the extension line of.

Therefore, the output value of the second multiplication circuit 45 is the point R on the extension of the straight line QS and the true zero point Z at the number of measurements B ″.
Is approximated to the length of a straight line RR ′ connecting the point R ′.

[0042] Therefore, the output value of the first multiplier circuit 25 represents the length of the straight line RM, since the output value of the second multiplier circuit 45 approximates the length of a straight line RR ', at the measurement times B ₃ The output of the adder circuit 26, which is obtained by adding the length of the straight line MR ′ to the output value Z ₃ of the zero point hold circuit 13, approximates to the true zero point Z at the number of measurements B ″.

Therefore, when only the zero point change degree is used, the value of the R point on the extension line of the straight line QS becomes the zero point, whereas when the zero point change degree is used, the quadratic curve of the actual zero point is used. The point R'which substantially follows the dynamic change is output as a zero point.

As described above, according to this circuit, the zero point with a small error following the quadratic curve change is determined by the addition circuit 2 depending on the degree of change of the zero point (reference value) change of the previous time and the previous two times.
6 is output, and this zero point is subtracted from the measured value of the weighing machine 12 by the third subtraction circuit 27, and the true weight is displayed on the display circuit 28.

Further, if the zero point is measured with the number of times of measurement B ₄ , the next degree of change can be obtained by the second degree of zero point change and the third degree of zero point change.

In the above embodiment, the case of the weight measuring device has been described, but it goes without saying that the present invention can be applied to a measuring device of length, flow rate and the like.

[0047]

As described above, in the reference point correction device of the present invention, the present reference point is calculated from the change of the reference point, so that the conventional reference point measurement is not necessary. , When the reference value changes in a quadratic curve, it is configured to consider the amount of change corresponding to the tendency of change using the degree of change in the reference value change corresponding to this quadratic curve change. An accurate reference point correction that substantially follows a quadratic curve change of is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing a timing signal.

FIG. 3 is an explanatory diagram of zero point correction when the zero point changes in a quadratic curve.

FIG. 4 is a block diagram showing a conventional zero correction device.

5 is an explanatory diagram of zero point correction by the conventional device of FIG.

[Explanation of symbols]

 11 Weighing pan 12 Metering device 13 Zero point hold circuit 14 Old zero point memory circuit 15 Switch 16 First subtraction circuit 17 Counter 19 Old frequency memory circuit 20 Switch 21 Subtractor circuit 22 First division circuit 23 Zero point change memory circuit 24 Switch 25 First multiplication circuit 26 Addition circuit 27 Third subtraction circuit 28 Display circuit 41 Second subtraction circuit 42 Second division circuit 43 Switch 44 Zero-point change degree storage circuit 45 Second multiplication circuit

Claims (1)

[Claims] 1. A measuring instrument for measuring an object to be measured and outputting a measured value, a reference value storage circuit for storing a constant load measurement value from the measuring instrument in a constant load state, and a storage in the reference value storage circuit. A first constant load measurement value at the time of the first constant load measurement performed and a second constant load measurement value from the measuring device in a second constant load state measured thereafter, And a first subtraction circuit for dividing the difference between the first and second constant load measurement values output from the first subtraction circuit by the difference in the number of measurements between the first and second constant load measurements . a division circuit, a reference value change degree storage circuit for storing an output value of said first divider circuit, a first reference value change degree stored in the reference value change degree storage circuit, second to the next , A difference between the third constant load measurement and the second reference value change degree output from the first division circuit is calculated. A second subtraction circuit and a second subtraction circuit for dividing the difference between the first and second reference value change degrees output from the second subtraction circuit by a difference in the number of times between the second and third constant load measurements. 2 division circuit, a reference value change change degree storage circuit that stores the output value of the second division circuit, the reference value change degree stored in the reference value change degree storage circuit, and A first multiplication circuit that multiplies a difference in the number of times of the third constant load measurement, and a change degree of the reference value change stored in the change degree storage circuit of the reference value change between the current measurement time and the third change time. A second multiplication circuit that multiplies the square of the number of times difference with the constant load measurement, and an output value of the first multiplication circuit and an output value of the second multiplication circuit in the reference value storage circuit. The addition circuit for adding to the stored constant load measurement value at the time of the third constant load measurement, And a third subtraction circuit for correcting the reference value by subtracting the output value of the addition circuit.