KR20120090264A - Calibration appratus and method thereof for measuring instrument - Google Patents

Abstract

PURPOSE: A calibration apparatus and method for a measuring instrument are provided to enhance accuracy of a measured value and to reduce error by automating a passive and classical method. CONSTITUTION: A measuring apparatus(10) comprises an input module(11), a sensor unit(12), an analog to digital converter(13), and a digital processor(14). The input module inputs a measured input signal to the measuring apparatus. The sensor unit measures the input signal of a measurement target and creates an analog signal. The analog to digital converter changes the analog signal into a digital signal. The digital processor establishes a sectional measuring point value and calculates an average measuring value. The digital processor compares the average measuring value with change rate of a measuring point value of a fixed section and creates a sectional change rate for the measured signal. The digital processor creates a collected measuring data value by applying the sectional change rate to a real measuring value.

Description

Calibration appratus and method approximate for measuring instrument

The present invention relates to a calibration method and apparatus for automatically adjusting and calculating measurement errors for precision measurement of a measuring instrument.

In general, power measurement equipment or equipment must be calibrated periodically due to the nature of the transformer. Conventional calibration methods include a hardware method using a variable resistor and a software method of adjusting and applying a gain value in a program.

The hardware method is simple but the process is not accurate enough because it is a manual process, and the method of adjusting the gain value in the program also depends on the judgment of the coordinator.

In addition, when the error is not constant for each section according to the measurement range, even if the zero adjustment, the error according to the section may occur.

The present invention is to provide a calibration method and apparatus for measurement to increase the accuracy of the measurement by utilizing multiple points for each section of the measurement equipment, to obtain the consistency of the adjustment value by automating the calibration.

The present invention is to provide a calibration method and apparatus for measurement that can reduce the measurement error according to the measurement range.

According to an aspect of the present invention, by measuring the measurement range of the measuring instrument for each section measuring point value (N ₁ , N ₂ N ₃ . N _{N -1} N _n ) A first step of setting a second step of receiving a reference value corresponding to the measurement point value for each section, and storing the average effective value averaged by measuring the input measurement value for a predetermined measurement time; Repeating the second step by a predetermined number of measurements, and averaging them to average the measured values N _{1rms ,} N _2rms N _3rms … N _{N -1 rms} A third step of calculating and storing N _nrms ); Each piecewise change the following formula 1 (wherein 1: _(n N ~ N _{N -1} interval change rate ₌ (N _n -N _{N -1} ) / N _nrms A fourth step of operating after N _{N -1 rms} ) and storing the value; A fifth step of receiving an actual measurement value with respect to a value to be measured; And a sixth step of outputting the corrected measured value by applying the interval change rate of the corresponding section with respect to the actual measured value.

According to another aspect of the present invention, by measuring the measurement range of the measuring instrument for each section measuring point value (N _{1 ,} N ₂ N ₃ … N _{N -1} N _n ) Means for setting; Means for receiving a reference value corresponding to the measurement point value for each section, and storing the average effective value averaged by measuring the input measurement value for a predetermined measurement time; The average effective value is repeatedly measured for a predetermined number of measurement times, and the average is measured to average the measured mean values N _1rms , N _2rms N _3rms … N _{N -1 rms Means} for calculating and storing N _nrms ); Each piecewise rate the following equation (Equation 1-1) N ~ N _{n n -1} of period interval change rate = measured period of the change point value _{(N n - N N -1)} / period of the average measurement value amount of change (N _nrms - N _{N -1 rms} ) and means for storing the value thereafter; Means for receiving an actual measurement value with respect to a value to be measured; And a means for outputting the corrected measured value by applying the section change rate of the corresponding section with respect to the actual measured value.

According to another aspect of the invention, the input module unit for inputting the measured input signal to the device; A sensor unit measuring an input signal through the input module and generating an analog signal with respect to the measured signal; A converter unit converting the analog signal into digital data; The digital processor calculates the interval change rate by calculating the average value for each interval set for the digital data at a set number of times, comparing the reference value with each interval, and applying the interval rate of change to the actual measured value to generate the measured data value. A memory unit for storing the digital data, a reference value for each section, and a section change rate; A central processing unit which controls the operation of each unit according to a program including the input module unit, a sensor unit, a converter unit, a digital processor unit, and a memory unit; Measurement point value setting, measurement time, measurement frequency for each section required for calibration. An input / output interface unit configured to allow a user to input environmental conditions and command conditions, and output a calculation and measurement data; There is provided a measurement calibration device comprising a.

According to an embodiment of the present invention, the analog signal converted from the measuring transformer (PT: voltage, CT: current) is utilized as a source for utilizing the digital data converted through the A / D converter for display or various application calculations. By automating the classical, manual method of calibrating a measuring instrument or facility, it is effective to reduce errors and maintain measurement consistency.

In addition, there is an effect that can implement a calibrated measurement value by automatically correcting the error for each section even in the instrument having a different error for each section.

The method proposed in one embodiment of the present invention automatically maintains the same quality since the calibration is performed, and has the effect of reducing the working time due to the calibration because the channel is performed simultaneously.

1 is a schematic block diagram of a measuring apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating a measurement method according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, "includes." Or “having”, etc., are intended to indicate the presence of a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other features or numbers, steps, actions, configurations It is to be understood that it does not preclude the presence or possibility of addition of elements, parts or combinations thereof.

Certain exemplary embodiments will now be described in order to provide an overall understanding of the functionality and principles of use of the methods and apparatus disclosed herein. One or more examples of these embodiments are shown in the accompanying drawings.

The structures specifically described herein and shown in the accompanying drawings are merely exemplary embodiments, and features shown or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

One embodiment of the present invention is described in connection with a power measurement method and apparatus, but the method and apparatus may be applied to all measurement equipment such as all frequency measurement or metering apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram of a measuring apparatus according to an embodiment of the present invention.

The calibration device 1 for measurement according to an embodiment of the present invention includes a measurement device 10 and an electrostatic source generator 30.

The measuring device 10 includes an input module 11, a sensor unit 12, an A / D converter unit 13, a memory unit 15, 16, 18, a digital processor (DSP 14), a central processing unit 17, It comprises an input / output interface device (HMI 19), a power module 20.

The input module 11 is a module for inputting an input signal such as a voltage or a current to be measured through an input probe or an input code into a device.

A constant voltage and a constant current are input through the input module 11 to perform calibration from the electrostatic power source generator, and an input signal of a measurement target is input.

The sensor unit 12 measures current and voltage signals of DC and AC input through the input module, and generates analog signals corresponding to the measured signals. This signal is converted into a digital signal through the A / D converter unit 13.

The digital processor DSP 14 calculates the average rate of the effective value of the measured data according to the processor and compares it with the calibration reference value (reference value) to generate a rate of change for each section.

In addition, the values of the above sections are used to calculate the gain value for each section, and the DSP determines the section for the input and measured value, and calibrated by applying and correcting the section's rate of change for the section. Generate signal values.

The memory unit is divided into a temporary memory (MEM-C 18) for temporarily storing measured data, a main memory (16) for storing processing programs and data, and a fixed memory (MEM-D 15) for permanently storing setting values.

The central processing unit (CPU 17) controls the operation of each device.

The input / output interface device (HMI (Human Machine Interface) 19) sets the measurement point value for each section, measurement time, and measurement frequency. This function allows the user to input environmental conditions and command conditions, and outputs calculation and measurement data.

The electrostatic source generator 30 is a device for generating a standard signal, and is a device for generating a rated signal for each level of DC and AC current and voltage signals.

The electrostatic source generator 30 may be included in the above-described measurement apparatus 10 or may be configured as a separate device.

The operation of the apparatus with respect to FIG. 1 will now be described.

The electrostatic source generator 30 is a device that can output the correct standard AC voltage / current and DC voltage / current in multiple channels at a value set by a user.

First, in order to perform a calibration operation, the set output of the electrostatic source generator 30 corresponding to the reference value generator of voltage and current is connected to the input module 11 of the measuring device 10.

According to another embodiment of the present invention, the input module 11 and the sensor unit 12 is composed of a multi-channel capable of generating a signal by measuring different channels at the same time to perform simultaneous calibration by measuring the multi-channel It becomes possible.

That is, the sensor unit 12 includes a sensor circuit corresponding to each channel.

The measuring device 10 has a function of performing a calibration operation through the HMI 19, and the main role of the HMI 19 is a progress state and a corresponding input channel and environment setting during the calibration operation. .

First, check the current and voltage measurement range (magnification) of the DC and AC of the input module 11 to be calibrated, and then calculate the magnification and calibration step order and calibration reference value through the HMI 19 in the electrostatic generator 30. Value) and save it in memory (MEM-C 18).

After connecting the electrostatic generator 30 and the input module (11) as described above, the measurement point value (N ₁ , N ₂ , N ₃ … N _{N −1} ,) for each section for outputting the calibration reference value of each calibration step. N _n ).

When the AC and DC voltage / current sources having the reference value corresponding to the first level reference value are input to the measuring device 10, the analog measuring signal is generated by each measuring sensor in the sensor unit 12.

The measured signal is converted into data through the AD converter (13), which is compared with the reference value (reference value) after the rms (average value of the effective value) operation in the DSP (Digital Signal Processor) 14 (N _1rms , N _2rms , N _3rms … N _{N -1 rms} , N _nrms ) and change rate (gain value) for each section are generated.

When gain values for all channels are generated, the DSP 14 stores a message about completion of work in the main memory 16 and transmits an interrupt signal for completion of storage to the CPU 17.

Upon receiving the interrupt signal, the CPU 17 shows the waiting guide for performing the next step to the HMI 19 and waits for the user's control. The calibration operation can be monitored in real time through the HMI 19, and as described above, the user interface for standby and progression (HMI) allows the user to adjust the output voltage / current of the electrostatic generator 30 at each step. ).

After completing the calibration steps set by the user, a message of completion of calibration is displayed on the HMI 19, and all set values are stored in the fixed memory (MEM-D, 15) of the measuring device 10 and applied to actual measurement. Becomes

According to the exemplary embodiment of the present invention, the signal measured by the analog transformer through the constant voltage generator 30 is generated as digital data in the preprocessing process, and the input value is obtained by comparing the input value with the output value. The calibration operation for outputting the same value as can be performed automatically.

Typically, voltage is rated at 63.5 Vac (154 kV) or 66.4 Vac (345 kV) for power and 5 A or 1 A for current. The other transducer signals are the same, and the sensor must be prepared.

Each sensor may show different errors for each section of the measurement range.

Therefore, in the case of voltage, it is possible to maintain linearity with respect to standard measurement by setting and calibrating the measuring point by appropriate section. For example, in the case of voltage, specifying 5 steps, such as 10V / 63.5V / 120V / 170V / 220V, was the best place to maintain the linearity of the voltage measurement.

As a result of the test according to an embodiment, when the above steps were further subdivided and set to 6 or more steps, the time required for the calibration time became longer and there was no significant difference in the rate of change.

On the other hand, when the above step is reduced to 4 steps or less, the interval change rate is significantly different.

In the case of an electric current, it can determine by 0.05A / 0.1A / 1A / 5A / 10A etc. For example, the measurement point is not absolute, so if the user selects from the desired input range, the measurement value is more accurate than the conventional method.

In one embodiment of the present invention, the value for the calibration of voltage and current at one measurement point is determined by averaging about 60 root mean squares (rms) per second based on 60 Hz through about 20 counts. To obtain an optimal value.

However, it is possible to change the measurement time and the optimum number of measurements through user adjustment. In the case of the same transformer, it is effective to shorten the working time when the parallel connection is performed in parallel. In the exemplary embodiment of the present invention, an optimal value is obtained by performing 5 steps in the case of the measuring point, but this may also be designated according to the user's judgment.

In the present invention, the most important process for performing automatic calibration is to obtain a "Calibration Slope" by averaging the measured rms data and matching the measured data with the input value. Calibration Slope is literally a rate of change calculation for calibration, which is the amount of change in the input value divided by the rate of change in the measured value. This function is used to calculate the rate of change after storing the average value measured about 20 times per second in a specific memory buffer.If this value is found, the same procedure is performed on other channels with the same transformer and the next calibration is performed. You will wait until your points are ready.

2 is a flowchart illustrating a method of measuring voltage and current according to an embodiment of the present invention.

First, when the START (100) is started in step 100, in step 101, after all the preparation for calibration is completed, the set reference output of the electrostatic source generator 30 is connected to the input module (11) of the measuring device 10. .

Next, the channel calibration order of the AC voltage input module channel, the AC current input module channel, the DC voltage input module channel of the measurement device 10 is set (step 102).

Continued measurement point values in x steps N _{1 ,} N ₂ N _{3 .} N _{N -1} N _n are set (step 103). x is a step for calibration and can be set by the user through HMI.

For example, if x = 5, it has 5 levels of calibration gains. In case of AC voltage, Cal_Point can be set to 5 steps of 0 ~ 1V / 1 ~ 10V / 10V / 10 ~ 70V / 70 ~ 150/150 ~ 240V respectively when measuring from 0V to 240V.

Next, the digital signal processing of AC voltage / current and DC voltage / current, which are reference values, is input from the electrostatic power generator 30 to perform measurement and calculation (step 104).

Next, set the measurement time. When the measurement time is set to 1 sec, the rms measurement is measured for 1 second and input to the buffer (step 105).

Next, the number of measurements is set to obtain an average measured value for each section. If the count is set to 20 times, the above effective value / 1sec is repeated 20 times (20 seconds) and the average measured value for each section (N _1rms, N _2rms) N _3rms … N _{N -1 rms} N _nrms ) is obtained (step 106).

In the next step, a step (Cal_Slope) of each Cal_Point step is calculated by the following equation 1 (step 107).

[Formula 1]

Interval change rate of N _n ~ N _{n -1} interval = Interval change amount of measurement point value (N _n -N _{N -1} ) / Average change amount of average measured value (N _nrms - N _{N -1 rms} )

Next, the calculated interval change amount Cal_Slope is stored in the memory after calculating the gain value of each step (step 108). After calibration, the gain value of 5 steps is applied according to the 5 ranges of measurement ranges and used for precise measurement.

In the next step, when the calibration operation and the gain value calculation of the step are completed, it waits for the standby and control input command through the HMI to perform the next step (measurement range) (step 109).

The next step proceeds according to the next step command via the HMI (step 110). The same process is performed for other channels with the same transformer. The HMI will wait until the next calibration point is ready. In addition, when all the steps are completed (END).

The calibration method according to an embodiment of the present invention will be described with reference to actual application examples.

When the input signal acceptable in the measuring device is AC voltage / current and DC voltage / current, it is assumed that the calibration point for each sensor is 5 steps, and the calibration point for each sensor is set as follows.

[AC voltage calibration points: 10, 63.5, 120, 170, 220V]

[AC Current Calibration Points: 0.02, 0.1, 0.5, 5, 12.5A]

[DC 4-20mA Calibration Points: 4, 8, 12, 16, 20mA]

[DC -10 ~ 10V Calibration Points: -10, -5, 0, 5, 10V]

When 10Vac is applied to the voltage input channel as the electrostatic power generator in the set state as described above, the digital data through the AD converter is calculated as an effective value (rms) of one cycle. (The effective value measurement time was set to 1 sec and the measurement frequency was set to 20 times.)

When converted to the effective value, it is put in the buffer for the channel and moves on to the next channel. In the next channel, the source corresponding to the sensor is input, AD conversion is performed, and the effective value is calculated and put in the buffer. This process is performed for 1 second to perform average value rms processing for 1 second. The data is averaged for 1 second and put in the average value buffer. This procedure was performed 20 times (20 seconds), and the average buffer value was divided by 20 to determine the final measured rms value.

Once the final value for 10V is stored in memory, repeat the same process for the next step, 63.5V. When the final measured rms value for 120V, 170V, and 220V is completed, a slope value is calculated to calculate a calibration gain value. The rate of change is divided into 10V or less, 10V ~ 63.5V section, 63.5V ~ 120V section, 120V ~ 170V section, and finally 170V ~ 220V section according to the set measurement point.

The results of the reference value and the final measurement (rms) value according to the above embodiment are shown in Table 1 below.

Measurement of reference reference value for AC voltage Reference value (reference value) 10 V 63.5 V 120 V 170 V 220 V Measurement average value 10.5V 64.1 V 120.2V 169.8 V 220.5V

Using the reference value (reference value) above, DSP performs calculation on the rate of change for each section as follows and outputs the result.

The rate of change in 1 section is 10-0 / 10.5-0 = 0.952380

The rate of change in the second section is 63.5-10 / 64.1-10.5 = 0.81156

The rate of change in the three sections is 120-63.5 / 120.2-64.1 = 1.00713

Four-section change rate is 170-120 / 169.8-120.2 = 1.00806

The 5-section change rate is 220-170 / 220.5-169.8 = 0.986193

The value of each section is used to calculate the gain value for each final section, and the measurement device first grasps the section when measuring voltage and then applies the gain of the section and calibrate to display the precise measured value.

Will be

For example, if the actual voltage measurement is recognized as 87V in the measuring instrument sensor with the calibration value as above, it is 3 divisions, so apply the rate of change of the three divisions (1.00713) to 87 * 1.00713 = 87.62V It is calibrated and precisely measured.

If the calibration measurement method according to an embodiment of the present invention is applied, the periodic calibration of various measurement equipment and facilities having the same function will be simpler than before, and the same quality of measurement can be maintained.

In addition, the method proposed in one embodiment of the present invention can automatically maintain the same quality, and has the effect of shortening the working time because it performs multiple channels simultaneously.

According to an embodiment of the present invention, the analog signal converted from the measuring transformer (PT: voltage, CT: current) is utilized as a source for utilizing the digital data converted through the A / D converter for display or various application calculations. By automating the classical, manual method of calibrating a measuring instrument or facility, it is effective to reduce errors and maintain measurement consistency.

In addition, there is an effect that can implement a calibrated measurement value by automatically correcting the error for each section even in the instrument having a different error for each section.

10 .: Instrument
11: input module
12 .: sensor
13: A / D converter
14: Digital Signal Processor
15, 16, 18: Memory section
17: central processing unit
19: Input and output interface unit (HMI)
20: power supply module
30: electrostatic source generator
32: AC voltage generation operation unit
33: AC current generating operation portion
34: DC voltage generation operation unit
35: DC current generating operation portion

Claims (10)

Allocates the measuring range of the instrument and measures the measurement point value _per section (N _{1 ,} N ₂ N ₃ … N _{N -1} N _n ) First step to set up:
Receiving a reference value corresponding to the measurement point value for each section, and storing the average effective value obtained by measuring and averaging the measured value of the input reference value for a predetermined measurement time;
Repeating the second step by a predetermined number of measurement times and averaging the average measured values N _{1rms and} N _2rms N _3rms … N _{N -1 rms} N _nrms );
A fourth step of calculating the rate of change for each section by the following Equation 1 and storing the value;
Equation 1) Rate of change of interval between N _n ~ N _{n -1} = Interval change amount of measurement point value (Nn-N _N-1 ) / Interval change amount of average measured value (N _nrms - N _{N -1 rms} )
A fifth step of receiving an actual measurement value with respect to a value to be measured;
A sixth step of outputting a corrected measurement value by applying a section change rate of a corresponding section to the actual measured value; Calibration method for measuring, comprising a
The method of claim 1,
The measurement point value is a calibration method for measurement, characterized in that the five sections of AC voltage 10, 63.5, 120, 170, 220 [V]
The method of claim 1,
The measurement point value is a calibration method for measurement, characterized in that the five sections of AC current 0.02, 0.1, 0.5, 5, 12.5 [A]
The method of claim 1,
The measurement point value is a calibration method for measurement, characterized in that the five sections of DC current 4, 8, 12, 16, 20 [mA]
The method of claim 1,
The measurement point value is a calibration method for measurement, characterized in that the five sections of the DC voltage -10, -5, 0, 5, 10V]
The method according to any one of claims 1 to 5,
The measurement time is 1 sec, and the measurement number is 20 times the calibration method for measurement
Allocate the measuring range of the instrument and measure the measurement point values (N _{1 ,} N ₂ , N ₃ … N _{n -1} , N _n ) for each section. Means for setting;
Means for receiving a reference value corresponding to the measurement point value for each section, and calculating an average effective value obtained by measuring the input measurement value of the reference value for a predetermined measurement time;
Means for repeating the average effective value for a predetermined number of measurement times, and averaging the average effective value to calculate average measured values (N _1rms , N _2rms , N _3rms ,... N _{N -1 rms} , N _nrms ) for each section;
Means for calculating a rate of change for each section by the following equation 1-1;
Equation 1-1) Interval change rate of interval N _n ~ N _{n -1} = Interval change amount of measurement point value (N _n -N _N-1 ) / Interval change amount of average measured value (N _nrms - N _{N -1 rms} )
Means for storing the measurement point value for each section, the average effective value, the average measured value, and the rate of change for each section;
Means for receiving an actual measurement value with respect to a value to be measured;
Means for outputting a corrected measurement value by applying the section change rate of a corresponding section to the actual measured value; Calibration device for measuring, comprising a
An input module unit for inputting the measured input signal to the device;
A sensor unit measuring an input signal of a measurement target through the input module and generating an analog signal with respect to the measured signal;
A converter unit converting the analog signal into digital data;
Set the measurement point value for each section, obtain the average value of the measured value of the section-specific reference value by the digital data, calculate the average measured value by calculating the predetermined number of times, the rate of change of the measurement point value of the set section A digital processor configured to generate a section change rate of the measured signal in comparison with the control unit, and generate measured data values corrected by applying the section change rate to an actual measured value;
A memory unit which stores the digital data, the reference value for each section, and the section change rate;
A central processing unit for controlling operations of the input module unit, sensor unit, converter unit, digital processor unit, and memory unit according to a program;
An input / output interface unit for setting a measurement point value for each section required for calibration, a function of inputting a measurement time, a measurement frequency, an environmental condition, a command condition, and a function of outputting calculation and measurement data; Calibration device for measuring, comprising a
The method of claim 8,
The calibration device for measurement, characterized in that it further comprises an electrostatic source generator for generating the reference value for each section to a constant electrostatic source
The method of claim 9
The electrostatic source generator generates a signal of the reference value for the current and voltage of the DC, AC in multiple channels at the same time, the sensor unit for the calibration device, characterized in that provided with a sensor circuit for each of the multi-channel

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