CN113203709B - Interface detection method based on optical interface detector - Google Patents

Abstract

The invention provides an interface detection method based on an optical interface detector, which adopts a closed-loop temperature control method to provide a constant temperature environment for a light-emitting device, so that the output light intensity of the light-emitting device is constant, and the reflected light intensity in different media is also constant, therefore, when a system runs for a long time, the stability of a reflected light signal is good, and a good guarantee is provided for the interface detection of the system; the automatic gain adjustment algorithm is adopted, the automatic amplification function of small signals has obvious effect in remote test, and for signals with small phase difference, the output percentage between the two signals is increased by using the output signal amplification principle, so that the signals with small phase difference can be obviously distinguished; when the length of the optical fiber is respectively 10m and 2km, the five media of effluent, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil can be accurately distinguished, the difference value between the 92# gasoline and the 98# gasoline reaches 20%, the test consistency is good, and the test data is stable.

Description

Interface detection method based on optical interface detector

Technical Field

The invention relates to a method for detecting an oil mixing interface during oil product sequential delivery in a finished oil pipeline, in particular to an interface detection method based on an optical interface detector.

Background

At present, in the transportation of the finished oil, pipeline transportation has the advantages of high efficiency, low cost, less pollution and the like, and becomes a mainstream transportation mode in the finished oil transportation industry. The transportation of the finished oil pipeline generally adopts a sequential transportation mode, two media are freely diffused in the transportation process, an oil mixing section is inevitably generated, the oil mixing section is accurately and timely found, and the method plays an important role in the quality of the finished oil. The existing oil mixing interface detection methods comprise several methods, one method is that difference spectrum calculation is carried out according to absorbance A1 of an oil sample in a certain wavelength range measured by a near infrared spectrum and absorbance A0 of n-pentane in the same wavelength range measured by n-pentane, and the oil mixing interface is judged according to the value; the other method is a method for judging the position of the oil mixing interface by adopting a segmented pipeline model based on a dynamic equivalent pipeline length theory and correcting the judgment process by using density value change measured by a density instrument. The detection principles applied by various detection methods are different, and the detection effect and the complexity are also different.

The optical interface instrument adopts an optical fiber end face measuring technology, namely, the difference between the outgoing light intensity and the incoming light intensity of the optical fiber end face caused by the change of the liquid property is measured to detect the reflected light intensity of different oil products, the reflected light intensity of the different oil products is measured, and then the calibration is carried out in advance according to the measured value, so that the accurate judgment of the oil mixing interface is realized. The detection principle has the advantages that the detection method is simple, the influence of pipeline impurities is avoided, the test result is only related to the property of the liquid, the test result is more accurate and visual, and the like.

However, the optical interface instrument also has the following disadvantages:

(1) The light emitting device (semiconductor laser) is sensitive to temperature change, and generally, the temperature can affect the light emitting wavelength, the light emitting intensity, the service life and the like of the light emitting device, so that the intensity of reflected light is affected, and the accurate detection and judgment of signals are very unfavorable;

(2) When the measuring point of the optical fiber probe is far away, the reflected optical signal is very weak due to the large attenuation of the long-distance optical fiber, and if the signal is directly used, the phenomenon that the interface cannot be distinguished can be caused;

(3) When the properties of the two media are relatively close, the amplitude difference of the collected optical signals is not large, and if the signals are directly output, the interface distinction is not obvious, so that interface misjudgment can be caused.

Disclosure of Invention

The invention provides an interface detection method based on an optical interface detector, which is used for solving the problems of very weak optical signal, large signal fluctuation, instability and low resolution when the prior art is applied to an oil interface intelligent detector, and adopts the following technical scheme:

the invention provides an interface detection method based on an optical interface detector, which comprises the following steps:

(1) And adjusting the temperature in the control box by adopting closed-loop temperature control.

(2) Calibrating and calibrating the probe: respectively inserting probes of an intelligent oil interface detector into standard water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil to obtain calibration light reflection signal values, amplifying the percentage difference value between the calibration light reflection signal values with small difference, and outputting the amplified percentage value to a DCS (distributed control system) in the form of analog quantity 4-20 mA; the method comprises the following steps of collecting a light reflection signal value Vi of an oil product interface intelligent detector probe, comparing the signal value with preset values of various media, judging which two signals the signal value falls between, calculating the output percentage of a test signal according to a linear interpolation principle, and calculating the formula as follows:

in the formula：V _i-1 ≤V _i ≤V _i+1 I is not less than 0 and not more than 6, and V ₀ ＝0V，V ₆ ＝5V，P ₀ ＝0％，P ₆ ＝100％；P _i-1 And P _i+1 Are each V _i-1 And V _i+1 The corresponding percentage.

(3) And judging whether the length of the optical fiber of the oil product interface intelligent detector is more than 2km or not and outputting a result V directly when the length of the optical fiber is less than 2km.

(4) When the length of the optical fiber of the oil product interface intelligent detector is more than 2km, the signal output result is enhanced by using an automatic gain adjustment method.

In the invention, the six media of water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil have the following original test data and output percentages:

medium	Original signal (V)	Percent original (%)
			Water (W)	4.29	95
95# gasoline	2.32	42
			No. 92 gasoline	2.06	35
98# gasoline	2.01	33
			0# diesel oil	0.94	5

And (3) amplifying the percentage difference between the output percentages of the two mediums of the No. 92 gasoline and the No. 98 gasoline, outputting the two mediums into a DCS in the form of analog quantity (4-20) mA, and increasing the output percentage set values of the No. 92 gasoline and the No. 98 gasoline.

Medium	Original signal (V)	Set percentage (%)	Calculating output signal (mA)
				Water (W)	4.29	95	19.12
95# gasoline	2.32	75	15.61
				92# gasoline	2.06	60	12.6
98# gasoline	2.01	30	8.71
				0# diesel oil	0.94	10	5.6

Furthermore, the closed-loop temperature control method in the step (1) is to adjust the PWM output percentage so as to control the on-off of the heater, finally, the area is in a constant temperature state, when the temperature difference between the actual temperature and the target temperature is more than 7 ℃, full-speed heating is adopted, the system heating time is saved, and when the temperature difference is less than 7 ℃, the closed-loop temperature control adjustment heating is carried out.

In the invention, the following experimental steps are adopted for calibration:

(1) The output end and the input end of the optical fiber probe are respectively connected with the light transmitting and receiving device in the control box, the distance between the probe and the control box is 10m, and the output signal of the control box is connected to a DCS end.

(2) Several bottles which are completely shielded from light are prepared, several mediums to be detected are respectively filled in the bottles and marked, and the mediums can not be seen in the process.

(3) The optical fiber probe is wiped clean, the control box is powered on, the system temperature is set, the temperature in the control box is waited to be constant, then the probe is inserted into water, and at the moment, the screen of the control box can display a signal value and record the value.

(4) The probe was inserted into 95# petrol, 92# petrol, 98# petrol and 0# diesel in sequence and the signal magnitude recorded separately, during which the probe was wiped each time before insertion into the medium.

(5) Signals measured by five media, namely water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil, and corresponding output percentages are loaded into a control algorithm.

(6) And the probe is inserted into the media respectively, the percentage displayed by the control box is recorded, different media can be distinguished according to the percentage, and the curve change of the different media can be obviously seen in the DCS interface.

Further, the step (4) initializes the ADC chip, and then configures the AD gain, G =1, s_flag =1; collecting optical fiber return signals, collecting a plurality of optical fiber return signals in total, and collecting the optical fiber return signals once every 30 mS; obtaining V0 by adopting a median average filtering method for a plurality of collected numerical values; judging whether s _ Flag =0 or not, and if s _ Flag =0, directly displaying the signal V; if s _ Flag is not equal to 0, V0 < 0.25V, configure AD gain, G =16,s _flag =0; if 0.25V < V0 < 0.5V, AD gain is configured, G =8,s_flag =0; if 0.5V < V0 < 0.8V, AD gain is configured, G =4,s _flag =0; if 0.8V < V0, directly displaying the signal V; and (3) for s _ Flag not equal to 0,0.25V < V0 < 0.8V, the AD gain is reconfigured, and then the step (2) is returned to acquire the fiber return value again.

Furthermore, in the step (4), 10 numerical values are collected in total, the length of an optical fiber of the intelligent oil interface detector is more than 2km, and a signal automatic gain adjusting method is used when an output signal is less than 0.8V.

The invention has the beneficial effects that:

the interface detection method based on the optical interface detector provided by the invention adopts a closed-loop temperature control algorithm to provide a constant temperature environment for the light-emitting device, so that the output light intensity of the light-emitting device is constant, and the reflected light intensity in different media is also constant, therefore, when the system runs for a long time, the stability of the reflected light signal is good, and a good guarantee is provided for the system interface detection.

The method of the invention adopts an automatic gain adjustment algorithm, has obvious effect on the automatic amplification function of small signals during long-distance test, and ensures that the system meets both long-distance test and short-distance test, and the maximum distance can reach 2km.

The method is flexible to apply, the number of the media to be measured can be adjusted, the corresponding output percentage can be set randomly, and the percentage of the output signal is calculated according to the linear interpolation principle, so that different media can be judged; for the signals with smaller phase difference, the output percentage between the signals with smaller phase difference is increased by using the output signal amplification principle, so that the signals with smaller phase difference can be obviously distinguished;

the method disclosed by the invention is verified by tests, when the lengths of the optical fibers are respectively 10m and 2km, the five media of water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil can be accurately distinguished, the difference value between the 92# gasoline and the 98# gasoline reaches 20%, the test consistency is good, and the test data is stable.

Drawings

FIG. 1 is a schematic block diagram of the system of the present invention;

FIG. 2 is a flow chart of temperature control regulation according to the present invention;

FIG. 3 is a flow chart of the automatic gain adjustment of the present invention;

FIG. 4 is a schematic diagram of the calibration algorithm of the present invention;

FIG. 5 is an actual view of the interface from No. 92 gasoline to No. 0 diesel fuel according to the present invention.

Detailed Description

The present application is further described with reference to the accompanying drawings and the detailed description, and it should be noted that, in the present application, the embodiments or technical features described below may be arbitrarily combined to form a new embodiment without conflict.

In the description of the embodiments of the present invention, it should be noted that the terms "central", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and "upright", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the embodiments of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; the connection may be direct or indirect via an intermediate medium, and the connection may be internal to the two components. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, in the description of the embodiments of the present invention, the meaning of "a plurality", and "a plurality" is two or more unless otherwise specified. The descriptions referring to "first", "second", etc. are for descriptive purposes only, not specifically referring to sequential or ordinal meanings, and not for limiting the present invention, but merely for distinguishing between components or operations described in the same technical terms, and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

The materials, apparatus and methods used in the following examples, which are not specifically illustrated, are all conventional in the art and are commercially available.

The first embodiment is as follows: the invention relates to a calibration and test method

As shown in the attached figure 1 of the specification:

the method comprises the following steps: respectively connecting the output end and the input end of an optical fiber probe with a light transmitting and receiving device in a control box, wherein the distance between the probe and the control box is 10m (2 km), and connecting the output signal of the control box to a DCS end;

step two: preparing a plurality of completely lightproof bottles, respectively filling a plurality of mediums to be detected into the bottles, and marking, wherein the mediums cannot be exposed to light in the process, the better the lightproof degree of the bottles is, and the higher the accuracy of the test result is;

step three: cleaning an optical fiber probe, electrifying a control box, setting the temperature of a system, waiting for the temperature in the control box to be constant, then inserting the probe into water, displaying a signal value on a screen of the control box at the moment, and recording the value;

step four: sequentially inserting the probe into 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil, and respectively recording the signal size, wherein the probe needs to be wiped before being inserted into a medium each time in the process;

step five: signals measured by five media, namely water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil, and corresponding output percentages are loaded into a control algorithm;

step six: and the probe is inserted into the media respectively, the percentage displayed by the control box is recorded, different media can be distinguished according to the percentage, and the curve change of the different media can be obviously seen in the DCS interface.

Example two: the invention relates to an interface detection method based on an optical interface detector

(1) Temperature control

As shown in the attached figure 2 of the specification, heating, internal circulation and heat preservation and insulation treatment are carried out on a light-emitting and photoelectric conversion area in the control box, a temperature detection chip is arranged near the semiconductor laser, the real-time temperature of the area can be obtained, and the PWM output percentage is adjusted by adopting a closed-loop temperature control algorithm according to the temperature and the set temperature, so that the on-off of the heater is controlled, and finally the area is in a constant temperature state. When the difference between the actual temperature and the target temperature is larger than 7 ℃, full-speed heating is adopted, the heating time of the system is saved, and when the difference is smaller than 7 ℃, closed-loop temperature control adjustment heating is carried out.

(2) Automatic gain adjustment

As shown in the attached figure 3 of the specification, for a short-distance (less than or equal to 2 km) measuring point, the optical signal attenuation is small, and the measuring value is large; when the point is measured at a long distance, the optical signal attenuation is large, the test value is small, the difference between signals is small, medium discrimination is not facilitated, and in order to enable the system to adapt to all test distances, an automatic gain adjustment algorithm is used in a program.

The acquisition module selects a high-precision off-chip 24-bit ADC, the chip has a programmable gain function, the gain of the chip is configured according to the size of an original signal, and the signal is increased and displayed.

Because the reference of the chip is 5V, when the gain is 1, an original signal is collected, 10 data are obtained and then median average filtering processing is carried out, and then gain adjustment is carried out according to the following range:

V0<0.25V，G＝16；

0.25V≤V0<0.5V，G＝8；

0.5V≤V0<0.8V，G＝4；

v0 is more than or equal to 0.8V, and G =1; v0 is the filtered raw data and G is the gain.

After the AD gain is reconfigured, sampling is carried out again, and output and display are carried out. In general, when the measuring point is close to the control box, the output signal is more than 0.8V, and no gain adjustment is needed, and when the measuring point is far away from the control box, such as 2km, the output signal of the optical fiber is very small, and gain adjustment is needed. The automatic gain adjustment algorithm performed very well at the 2km test, as shown in table 2, the difference between the gasoline in comparison table 195# and 92# increased from 4mV to 90mV, greatly increasing the difference between the signals.

TABLE 1 Signal test results without automatic gain adjustment Algorithm

Medium	Optical fiber length 10m (V)	Optical fiber length 2km (V)
			Water (W)	4.33	0.27
95# gasoline	2.35	0.127
			No. 92 gasoline	2.08	0.123
98# gasoline	2.03	0.115
			0# diesel oil	0.95	0.096

TABLE 2 increase of signal test results of automatic gain adjustment algorithm

Medium	Optical fiber length 10m (V)	Optical fiber length 2km (V)
			Water (W)	4.29	2.2
95# gasoline	2.32	2.04
			92# gasoline	2.06	1.95
98# gasoline	2.01	1.84
			0# diesel oil	0.94	1.53

(3) Output signal amplification

As shown in the attached figure 4 of the specification, the reflected light intensities of the probes in different media are different, so that the signal measurement values (I/V) are different, if the probes are respectively placed in water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil, the test data is shown in a table 3, the signals are directly output, and the output percentage is calculated and is shown in the table 3.

TABLE 3 media raw test data and percent output

Medium	Original signal (V)	Percent original (%)
			Water (W)	4.29	95
95# gasoline	2.32	42
			No. 92 gasoline	2.06	35
98# gasoline	2.01	33
			0# diesel oil	0.94	5

As can be seen from the above table, the output percentage difference between the two mediums of gasoline 92# and 98# is small, which is not beneficial to removing and distinguishing the two mediums, therefore, the algorithm adopts the output signal amplification principle, and the percentage difference between the two mediums is set to be large, so as to increase the output signal difference, and output the output signal difference to the DCS in the form of analog quantity (4-20) mA, as shown in Table 4.

TABLE 4 increase 92# and 98# output percentage set points

Medium	Original signal (V)	Set percentage (%)	Calculating output signal (mA)
				Water (W)	4.29	95	19.12
95# gasoline	2.32	75	15.61
				No. 92 gasoline	2.06	60	12.6
98# gasoline	2.01	30	8.71
				0# diesel oil	0.94	10	5.6

As can be seen from Table 4, the output percentages of gasoline No. 92 and gasoline No. 98 are increased from 2% to 30%, which is more favorable for the discrimination of the interface.

Before the method is used, parameter calibration is carried out in advance, during actual test, a control algorithm collects light reflection signals in real time, the value of the light reflection signals is Vi, the signal value is compared with a calibration parameter, the signal value is judged to fall between which two signals, the output percentage of the test signals is calculated according to a linear interpolation principle, and the formula is as follows:

in the formula: v _i-1 ≤V _i ≤V _i+1 I is not less than 0 and not more than 6, and V ₀ ＝0V，V ₆ ＝5V，P ₀ ＝0％，P ₆ ＝100％；

P _i-1 And P _i+1 Are each V _i-1 And V _i+1 The corresponding percentage.

And outputting the corresponding analog quantity according to the calculated percentage, as shown in the specification and figure 5.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (3)

1. An interface detection method based on an optical interface detector is characterized by comprising the following steps:

(1) Adjusting the temperature in the control box by adopting closed-loop temperature control; the closed-loop temperature control method is characterized in that the PWM output percentage is adjusted, so that the on-off of the heater is controlled, the control box is finally in a constant temperature state, when the actual temperature difference from the target temperature is larger than 7 ℃, full-speed heating is adopted, the heating time of the system is saved, and when the actual temperature difference is smaller than 7 ℃, closed-loop temperature control adjustment heating is carried out;

(2) Calibrating and calibrating the probe: respectively inserting probes of an intelligent oil interface detector into standard water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel to obtain calibrated light reflection signal values, setting and amplifying percentage differences among the calibrated light reflection signal values with small differences, and outputting the amplified percentages to a DCS (distributed control system) in an analog quantity of 4 mA-20mA mode; the method comprises the following steps of collecting a light reflection signal value Vi of an intelligent detector probe of an oil product interface, comparing the signal value with preset values of various media, judging which two signals the signal value falls between, and calculating the output percentage of a test signal according to a linear interpolation principle, wherein the formula is as follows:

formula 1

In the formula:

and->

The corresponding percentage;

(3) Judging whether the length of the optical fiber of the intelligent oil product interface detector is greater than 2km or not and outputting a result Vi directly when the length of the optical fiber is less than 2 km;

(4) When the length of an optical fiber of the intelligent oil product interface detector is more than 2km, enhancing a signal output result by using an automatic gain adjustment method;

the automatic gain adjustment method specifically comprises the following steps: initializing an ADC chip, and then configuring an AD gain, G =1, s _bFlag =1; collecting optical fiber return signals, collecting a plurality of optical fiber return signals in total, and collecting the optical fiber return signals once every 30 mS; v' is obtained by adopting a median average filtering method for a plurality of collected numerical values; judging that if s _ bFlag =0, directly displaying the signal Vi; configuring AD gain if s _ bFlag is not equal to 0,V' < 0.25V, G =16, s _bflag =0; if 0.25V < V' < 0.5V, AD gain is configured, G =8,s _bflag =0; if 0.5V < V' < 0.8V, AD gain is configured, G =4,s _bflag =0; if 0.8V < V', directly displaying the signal Vi; wherein G is the gain; for s _ bFlag not equal to 0,0.25V < V' < 0.8V, returning to the step (2) to re-collect the fiber return value after the AD gain is reconfigured;

the calibration also adopts the following experimental steps:

(1) Connecting the output end and the input end of the optical fiber probe with a light transmitting and receiving device in a control box respectively, wherein the distance between the probe and the control box is 10m, and connecting the output signal of the control box to a DCS end;

(2) Preparing a plurality of completely lightproof bottles, respectively filling a plurality of mediums to be detected into the bottles, and marking, wherein the mediums can not be exposed to light in the process;

(3) Cleaning an optical fiber probe, electrifying a control box, setting the temperature of a system, waiting for the temperature in the control box to be constant, then inserting the probe into water, displaying a signal value on a screen of the control box at the moment, and recording the value;

(4) Sequentially inserting the probe into 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil, and respectively recording the signal size, wherein the probe needs to be wiped before being inserted into a medium each time in the process;

(5) Signals measured by five media, namely water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel oil, and corresponding output percentages are loaded into a control algorithm;

(6) And the probe is inserted into the media respectively, the percentage displayed by the control box is recorded, different media can be distinguished according to the percentage, and the curve change of the different media can be obviously seen in the DCS interface.

2. The interface detection method based on the optical interface detector as claimed in claim 1, wherein the original test data and output percentage of six media of water, 95# gasoline, 92# gasoline, 98# gasoline and 0# diesel are as follows:

medium Original signal Original percentage Water (W) 4.29V 95% 95# gasoline 2.32V 42% No. 92 gasoline 2.06V 35% 98# gasoline 2.01V 33% 0# diesel oil 0.94V 5%

Amplifying the percentage difference between the output percentages of the 92# gasoline medium and the 98# gasoline medium, outputting the two mediums into a DCS in a mode of analog quantity 4-20mA, and increasing the output percentage set values of the 92# gasoline medium and the 98# gasoline medium;

medium Original signal Set percentage Calculating the output signal Water (W) 4.29V 95% 19.12mA 95# gasoline 2.32V 75% 15.61mA 92# gasoline 2.06V 60% 12.6mA 98# gasoline 2.01V 30% 8.71mA 0# diesel oil 0.94V 10% 5.6mA

。

3. The method as claimed in claim 2, wherein the step (4) acquires 10 values per group.

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