KR102485281B1 - Dampening and precision measurement system of incoming noise when measuring exposed analog sensors such as leaks - Google Patents

Abstract

The present invention relates to a system for reducing and precisely measuring an introduced noise when measuring an exposed analog sensor. According to the present invention, the system of the present invention precisely and accurately measures and monitors a signal of various types of an exposed sensor in real-time.

Description

Attenuation and precision measurement system for noise introduced during measurement of exposed analog sensors such as leaks and leaks

The present invention relates to attenuation of noise introduced during measurement of an exposed analog sensor such as leakage and leakage, and a precise measurement system through the same.

There is a risk of human, material, and economic accidents due to leaks of water, oil, or chemical liquids transported from facilities such as semiconductor factories, oil refineries, chemical factories, and water treatment plants to pipes connected to the facilities. .

A highly reliable real-time leak detection system for preventing such human, material, and economic damage is required.

Many domestic and foreign companies have released and installed related products, but they have problems with frequent errors due to noise, low accuracy, and very long detection time.

Therefore, there is a need for a system capable of accurate, precise and fast detection in real time.

Conventional measurement methods apply DC voltage or square wave voltage to the sensor, convert the current flowing through the sensor into voltage, remove high frequencies by an amplifier circuit and a long-time LPF circuit, and remove noise by methods such as long-term averaging.

However, if the sensor is directly exposed to a noise environment, such as an increase in length, measurement errors occur due to strong low-frequency noise, high-frequency noise, and impulse noise, which limits accurate and precise measurement.

The present invention aims to solve the above problems.

In addition, as a way to fundamentally escape the limitations of the prior implementation method, it is possible to configure a band pass filter (BPF) by using sinusoidal AC as the signal source of the sensor to filter low and high frequency noise. It is an object of the present invention to provide a precision measurement system through attenuation of noise introduced during measurement of an exposed analog sensor.

In addition, it is an object of the prior implementation method to provide a precision measurement system through attenuation of noise introduced during measurement of an exposed analog sensor that has fast response in real time by not using the long-term LPF applied to the circuit.

In addition, to compensate for temperature changes and circuit state changes, the circuit's self-gain is measured and applied as a reference value to provide high precision attenuation of noise introduced during measurement of an exposed analog sensor and a precision measurement system through this. is aimed at

In addition, the reduction of noise introduced during measurement of the exposed analog sensor and the precision measurement system through which the residual noise can be removed by the noise removal algorithm by receiving the same signal as the signal source of the frequency generated by the microprocessor It is intended to provide

According to one aspect of the attenuation of noise introduced during measurement of an exposed analog sensor according to the present invention for achieving the above object and a precision measurement system through this, a microprocessor; a digital-to-analog converter that converts the signal generated by the microprocessor into an AC signal of a sine wave having a predetermined frequency; a first buffer inputting the sinusoidal AC signal having a predetermined frequency generated by the digital-to-analog converter to an exposed sensor; a second buffer converting a current signal input into a circuit through the exposed sensor into a voltage; a multi-stage filter for filtering the signal converted into a voltage in the second buffer in multi-stage; and a full-wave rectifier receiving signals filtered in multiple stages by the multi-stage filter and performing full-wave rectification, wherein the microprocessor may measure a signal output from the full-wave rectifier.

An AC sine wave having a predetermined frequency by the microprocessor may be generated by an 11-bit high-speed digital-to-analog converter (DAC) of the R-2R ladder method, a low-pass filter (LPF), and a level shifter circuit.

The multi-stage filter may operate as a cascade-type multi-stage band-pass filter (BPF) that filters the signal converted to a voltage in the second buffer through a high-pass filter and a low-pass filter.

The microprocessor may measure a signal output from the full-wave rectifier through the high-pass filter and the low-pass filter.

A gain reference switch for inputting an AC reference signal source to the microprocessor through the multi-stage filter may be further included.

The microprocessor may store a signal input through the multi-stage filter as a gain reference value (Reference) by the gain reference value (Reference) switch.

The microprocessor changes the gain reference value (Reference) switch so that when the signal input through the exposed sensor is inputted through the multi-stage filter, arithmetic calculation is applied to the input signal based on the previously stored gain reference value (Reference). can

The microprocessor adds and averages the maximum value for each half cycle in order to compensate for the error according to the DC-Offset that exists according to the characteristics of the operational amplifier (OP Amp) applied to each buffer, filter, and full-wave rectifier. This can be used as an input signal.

The microprocessor may set the signal measurement period as a measured value by averaging data measured during 50mSec, which is the minimum crossing period between commercial power supply 60hz (16.6667mSec) and standard signal 500hz (2mSec) of the system.

Effects according to an embodiment of the present invention are described as follows.

According to the present invention, signals from various exposure sensors in industrial facilities can be accurately and accurately measured and monitored in real time with the system of the present invention.

In addition, when applied to leak sensor measurement, safety accidents can be prevented in advance to protect worker safety and facilities and bring economic benefits.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as part of the detailed description to aid understanding of the present invention, provide examples of the present invention and, together with the detailed description, describe the technical features of the present invention.
1 is a diagram showing the configuration of an analog sensor measurement system according to an embodiment of the present invention;
Figure 2 is a 500hz AC sine wave generation circuit diagram by the microprocessor in Figure 1 (Microprocessor).
3 is a circuit configuration diagram of an output buffer (BUFFER) and a microcurrent voltage conversion and gain reference value switch (Reference Switch) in FIG. 1;
4 is a circuit diagram of a band pass filter in FIG. 1;
5 is a circuit diagram of a full wave rectifier using an operational amplifier (OP-AMP) in FIG. 1;
6 is a diagram showing a sinusoidal signal of AC 500 Hz output by a sensor.
7 is a diagram showing an example of removing a DC offset by extracting a full-wave signal with a full-wave rectification circuit;
8 is a diagram illustrating an example of detecting and deleting noise finally remaining in a signal;

Hereinafter, the embodiments disclosed in the present invention will be described in detail with reference to the accompanying drawings, but the same or similar components are given the same reference numerals regardless of reference numerals, and redundant description thereof will be omitted. The suffixes "module" and "unit" for components used in the following description are given or used together in consideration of ease of writing the specification, and do not have meanings or roles that are distinct from each other by themselves. In addition, in describing the embodiments disclosed in the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the embodiments disclosed in the present invention, the detailed description will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in the present invention, the technical idea disclosed in the present invention is not limited by the accompanying drawings, and all changes included in the spirit and technical scope of the present invention , it should be understood to include equivalents or substitutes.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

1 is a diagram showing the configuration of an analog sensor measurement system according to an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a 500hz AC sine wave generation circuit by a microprocessor in FIG. 1, and FIG. 1 is a circuit diagram of an output buffer (BUFFER), microcurrent voltage conversion, and gain reference switch (Reference Switch), FIG. 4 is a circuit diagram of a band pass filter in FIG. 1, and FIG. 1 is a circuit diagram of a full wave rectifier using an operational amplifier (OP-AMP), and FIG. 6 is a diagram showing an AC 500Hz sinusoidal signal output by a sensor. FIG. 7 is a full wave signal with a full wave rectifier circuit. It is a diagram showing an example of extracting and removing a DC offset (DC OFFSET).

As shown, unlike conventional systems, the present invention may use an AC measurement method having a natural frequency as a signal source of a sensor, rather than a DC or square wave.

In the case of the conventional DC or square wave voltage measurement method, when placed in the air for a long time, a chemical reaction occurs at the air contact part of the sensor or particles such as dust adhere due to static electricity, deteriorating the function of the sensor.

In addition, since a long-term LPF circuit is applied to eliminate noise, real-time measurement is limited, and it is difficult to distinguish between a signal and noise when there is strong noise input.

The signal processing of the new AC voltage measurement method proposed in the present invention is described as follows.

A signal generated by the microprocessor 100 may generate a 500Hz sine wave AC through a digital-to-analog converter (DAC) 200.

An AC signal generated through the digital-to-analog converter (DAC) 200 may be input to the exposed R sensor 400 through the buffer A 300.

As shown in FIG. 2, the 500Hz AC sine wave generation circuit configuration by the microprocessor 100 is an R-2R ladder type 11-bit high-speed digital-to-analog converter (DAC), low-pass filter (LPF) & level shifter ) circuit.

The current signal input to the circuit through the R sensor 400 may be converted into a voltage through the buffer B 500.

The signal converted to voltage through buffer B 500 is passed through a high-pass filter (HPF) 610, a low-pass filter (LPF) 620, and then a high-pass filter (HPF, It goes through a multi-stage filter in the form of a cascade such as High-Pass filter (610) -> Low-Pass filter (LPF) (620), which is finally a band-pass filter (BPF, Band-Pass filter). A circuit that operates as a filter) (600) may be formed.

The input signal passed through the filter stages of the high-pass filter (HPF, Lo-Pass filter) 610 and the low-pass filter (LPF, 620) is converted into an OP-AMP full wave rectifier circuit (700 It is a system that can be measured in a microprocessor (100) through ).

The band pass filter (BPF) 600 may be configured with a circuit as shown in FIG. 4, and may have a cutoff frequency = 1/(2πRC). As shown in FIG. 5, the full wave rectifier circuit may be composed of a full wave rectifier circuit using an operational amplifier (OP-AMP).

By having such a circuit configuration, the present invention can have robustness against conductive and radiated noise of low frequency, high frequency, and impulse, which had limitations in precision measurement in conventional systems.

In addition, in the present invention, a solution to a change in circuit characteristics due to a change in ambient temperature and impulse noise is as follows.

Electrical characteristics of electronic components applied to buffers, filters, full-wave rectification circuits, etc. may change with temperature changes, and thus the overall gain may change.

In addition, since an abnormal voltage is charged in a capacitor on the circuit by the impulse noise, the stable state of the circuit tilts and it takes time to recover, and an error may occur while recovering to the stable state.

When the change values made up of multi-stage circuits are synthesized, the total gain greatly changes, so a gain reference input circuit can be added to solve this problem.

When the AC reference signal source is input to the microprocessor 100 through the filter circuit by the gain reference switch 800, the microprocessor 100 converts this input signal to the gain reference value ) can be saved.

Then, by changing the gain reference value (Reference) switch 800 and inputting the signal input through the R Sensor 400 to the Microprocessor 100 through the filter, the Microprocessor 100 can be applied by performing arithmetic calculation on the input signal based on a previously stored gain reference value.

The output buffer (BUFFER) and microcurrent-voltage conversion and gain reference value switch (Reference Switch) circuits may be configured as shown in FIG. 3 .

That is, as a solution to the error due to the change in gain due to temperature change and impulse noise, the signal output to the sensor is used as a gain reference signal and inputted to a band pass filter (BPF) by an analog switch and converted to an analog to digital converter. After reading the (ADC) value and saving it as the gain reference signal of the circuit, switch the switch to input the signal input from the sensor to the band pass filter (BPF), and perform arithmetic calculation on the size of the read analog-to-digital converter (ADC) value to input the sensor. It is possible to remove the error due to the gain change in the circuit by setting it as a value.

Calculated sensor input value = (ADC input value / ADC total value) x gain reference value

On the other hand, according to the present invention, signal measurement accuracy can be secured.

A DC-Offset value may exist according to characteristics of an operational amplifier (OP Amp) applied to each buffer stage, filter stage, and full-wave rectification circuit. In order to compensate for the error according to the DC offset (DC-Offset), the maximum value of each half cycle may be added and averaged, and this may be used as an input signal.

The measurement period can be measured by averaging the data measured during 50mSec, which is the crossing period of commercial power supply 60hz (16.6667mSec) and system standard signal 500hz (2mSec) (60msec in case of 50hz).

In addition, noise can be identified and deleted by a noise identification/removal algorithm.

Meanwhile, the entire algorithm for precise measurement of an analog sensor signal compared to the conventional method is as follows.

6 shows an AC sinusoidal signal of 500 Hz output by a sensor, and a multi-stage BPF circuit can be applied to the input signal of the sensor to remove noise and frequencies other than the measurement frequency of 500 Hz.

In addition, as shown in FIG. 7, in order to remove DC-Offset, a signal passing through a band-pass filter (BPF) is converted into a precise full-wave signal by a full-wave rectification circuit by an operational amplifier (OP Amp). After extraction, the final offset value can be removed by averaging the voltage magnitudes of the upper and lower sides of the AC waveform.

Sensor input value = (upper side size + lower side size) / 2

For example, in the full-wave rectified signal of FIG. 7, the largest value among 5 read values may be selected, and the DC-offset may be removed by using the average value of the two selected values as an input value.

On the other hand, a method for removing a measurement error of a waveform in which a measurement value increases and decreases due to a beat phenomenon caused by a phase difference between the noise of the remaining commercial frequency and the measurement period is as follows.

50msec (60msec in case of 50hz), in which phases of 60hz and 500hz coincide, may be determined as a measurement period.

An average value of 25/30 values during the measurement period (25/30 cycle) can be obtained to remove errors caused by the beating phenomenon.

500hz : 60hz = 25 : 3 (every 3 cycles of 60hz are in phase with 25 cycles of 500hz)

500hz : 50hz = 30 : 3 (every 3 cycles of 50hz coincide with 30 cycles of 500hz)

8 is a diagram illustrating an example of detecting and deleting noise finally remaining in a signal.

As shown, the average of 25 read values is obtained, and if a certain size differs from the average value of the previous period, it is determined as noise, deleted, and the average can be obtained.

That is, among 25 signals input at 50msec (60msec in case of 50hz), a value different from the average value can be found, determined as a noise signal, and removed from the signal.

The size of the signal to be processed as noise = The difference in size from the average value of the previous period (setting) or the difference from the average value of the current period (setting)

As described above, the present invention is a noise removal circuit design by H / W, generating an AC signal of 500Hz by a microprocessor, removing noise by applying a BPF (Band Pass Filter), , responds to the change in the overall gain of the circuit due to temperature change, responds to the inclination of the stability of the circuit due to impulse noise, and can apply a precise full wave rectifier.

In addition, as a noise removal algorithm by a microprocessor, an offset of a signal may be removed, a gain reference value may be set and timing controlled, and a noise removal algorithm may be applied.

The above detailed description should not be construed as limiting in all respects and should be considered illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

100: Microprocessor
200: digital-to-analog converter (DAC)
300: buffer A
400: R Sensor
500: buffer B
610: High-Pass filter (HPF)
620: Low-pass filter (LPF, Lo-Pass filter)
600: Band-Pass filter (BPF)
700: Full Wave Rectifier
800: gain reference value (Reference) switch

Claims (9)

As an attenuation of noise introduced during measurement of an exposed analog sensor and a precision measurement system through this,
microprocessor;
a digital-to-analog converter that converts the signal generated by the microprocessor into an AC signal of a sine wave having a predetermined frequency;
a first buffer inputting the sinusoidal AC signal having a predetermined frequency generated by the digital-to-analog converter to an exposed sensor;
a second buffer converting a current signal input into a circuit through the exposed sensor into a voltage;
a multi-stage filter for filtering the signal converted into a voltage in the second buffer in multi-stage; and
A full-wave rectifier receiving and full-wave rectifying the signal filtered in multiple stages by the multi-stage filter;
The microprocessor measures a signal output from the full-wave rectifier,
Further comprising a gain reference switch for inputting an AC reference signal source to the microprocessor through the multi-stage filter,
The microprocessor,
The signal input through the multi-stage filter by the gain reference value (Reference) switch is stored as a gain reference value (Reference), and the signal input through the exposed sensor is converted to the multi-stage filter by changing the gain reference value (Reference) switch. If it is input through
The microprocessor,
In order to compensate the error according to the DC-Offset that exists according to the characteristics of the operational amplifier (OP Amp) applied to each buffer, filter, and full-wave rectifier, the maximum value of each half cycle is added and averaged, and this is converted into an input signal The signal measurement period is the average of the measured data for 50mSec, which is the minimum crossing period of commercial power 60hz (16.6667mSec) and the standard signal 500hz (2mSec) of the system. Attenuation and precision measurement system through it.
The method of claim 1,
The AC sine wave having a predetermined frequency by the microprocessor is generated by an 11-bit high-speed digital-to-analog converter (DAC) of the R-2R ladder method, a low-pass filter (LPF), and a level shifter circuit. Reduction of noise introduced during measurement of analog sensor and precision measurement system through it
The method of claim 1,
The multi-stage filter,
Exposed analog characterized in that it operates as a multi-stage band-pass filter (BPF) for filtering the signal converted to voltage in the second buffer through a high-pass filter and a low-pass filter. Attenuation of noise introduced during sensor measurement and precision measurement system through it.
The method of claim 3,
The microprocessor,
Attenuation of noise introduced during measurement of an exposed analog sensor, characterized in that for measuring the signal output from the full-wave rectifier through the high-pass filter and the low-pass filter, and a precision measurement system through this. delete delete delete delete delete

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