CN115265724A - Field calibration device for liquid level gauge and method for obtaining calibration results - Google Patents

Abstract

The invention relates to an on-site calibration device for a liquid level gauge and a method for obtaining calibration results; it solves the problem that the use environment of the liquid level gauge existing in the prior art may be different from the conditions during laboratory calibration during the use process, resulting in There is a large error in the on-site measurement data, and the technical problem that the specific device used in the laboratory is not suitable to be brought to the field for measurement; the calibration device includes a liquid level control assembly, a standard device and a drain pipeline; the liquid level control assembly Connected with the tested liquid level gauge; one end of the drain pipeline is communicated with the lower end of the tested liquid level gauge, and the other end is communicated with external equipment; the standard device is communicated with the lower end of the tested liquid level gauge for realizing the The measurement and display of the pressure at the bottom of the liquid level gauge, the input and display of external information, the calculation and display of the liquid level h of the tested liquid level gauge, and the realization of the function of data clearing; the invention also proposes to obtain the calibration result on site Methods.

Description

On-site calibration device for liquid level gauge and method for obtaining calibration results

technical field

The invention relates to a liquid level gauge calibration device and method, in particular to a liquid level gauge calibration device on site and a method for obtaining a calibration result.

Background technique

For the existing liquid level gauge calibration method, see "JJG971-2019 Liquid Level Gauge Verification Regulations". Level gauge, other items in 7.1.1 are selected according to actual needs, and the specific verification method is introduced in 7.3.

The device and verification method proposed in the "JJG971-2019 Liquid Level Gauge Verification Regulations" are suitable for the laboratory environment. After the liquid level gauge to be used is removed, a specific device is used for measurement verification/calibration in the laboratory, but the liquid level gauge is in During use, its use environment may be different from the laboratory verification/calibration conditions, resulting in doubts about the accuracy of the final output results even though the measuring instruments are qualified, and even large errors. In addition, the liquid level gauge After transportation, it is easy to cause errors in on-site measurement data, and the specific devices used in the laboratory are usually bulky and expensive, and are not suitable for taking to the site for measurement. In order to realize the country's concept of vigorously strengthening industrial measurement work and ensure the accuracy and reliability of the final output data of measuring instruments, the demand for on-site/in-situ measurement is becoming more and more urgent.

Contents of the invention

The purpose of the present invention is to solve the situation that the use environment of the liquid level gauge in the prior art may be different from that of the laboratory calibration, which may cause doubts about the accuracy of the output results, and even lead to the existence of on-site measurement data. Due to the large error and the technical problems that the specific device used in the laboratory is usually bulky and expensive, it is not suitable to be taken to the site for measurement, and a liquid level gauge on-site calibration device and a method for obtaining calibration results are provided.

The technical scheme adopted in the present invention is:

An on-site calibration device for a liquid level gauge, which is special in that:

Including liquid level control components, standards and drain lines;

The liquid level control component communicates with the tested liquid level gauge, and is used for injecting liquid into the tested liquid level gauge and controlling the liquid level of the tested liquid level gauge;

One end of the liquid discharge pipeline communicates with the lower end of the tested liquid level gauge, and the other end communicates with external equipment for discharging the liquid in the tested liquid level gauge;

The standard device communicates with the lower end of the tested liquid level gauge, and is used to realize the measurement and display of the pressure on the bottom end of the tested liquid level gauge, realize the input and display of external information, and realize the adjustment of the liquid level h of the tested liquid level gauge. Calculate, display, and realize data clearing function, wherein the data includes pressure, external information and liquid level h, the external information includes liquid density ρ and gravity acceleration g, and the calculation formula of the liquid level h is h=p /(ρg).

Further, the standard device is a digital pressure gauge;

The digital manometer includes a memory, a processor, and a computer program stored in the memory and operable on the processor. When the processor executes the computer program, it realizes pressure measurement and display functions, and realizes external Information input and display, realize the calculation and display of the liquid level h of the tested liquid level gauge, and realize the function of data clearing, wherein the data includes pressure, external information and liquid level h, and the external information includes liquid density ρ and location The gravitational acceleration g, the calculation formula of the liquid level h is h=p/(ρg).

Further, the liquid level control assembly includes a tank body, a first pipeline, a second pipeline, and two first stop valves respectively arranged on the first pipeline and the second pipeline;

One end of the first pipeline communicates with the upper end of the tank body, and the other end communicates with the upper end of the liquid level gauge to be tested;

One end of the second pipeline communicates with the lower end of the tank body, and the other end communicates with the lower end of the liquid level gauge to be tested;

The tank is filled with liquid.

Further, the liquid level control assembly includes a pressure generator, a third pipeline, and a second stop valve arranged on the third pipeline;

One end of the third pipeline communicates with the lower end of the liquid level gauge to be tested, and the other end communicates with the pressure generator;

The cavity of the pressure generator is filled with liquid.

Further, it also includes a density meter for measuring the density of the liquid in the tank or the liquid in the chamber of the pressure generator.

Further, when the processor executes the computer program, it can also realize the function of displaying the usage amount of the pressure range.

The present invention also proposes a method for obtaining a calibration result of a liquid level gauge on site, which is special in that the above-mentioned on-site calibration device for a liquid level gauge comprises the following steps:

Step 1: Obtain the density ρ of the liquid and the acceleration of gravity g in the area where the liquid level gauge is used, and input the acceleration of gravity g and the density ρ of the liquid into the standard device;

Divide the range of the tested liquid level gauge equally to obtain i liquid level point values, among which, i≥3, the first liquid level point value is 0, and the i-th liquid level point value is the full scale value;

Step 2: Data Measurement

2.1 Inject liquid into the tested liquid level gauge, so that the liquid level in the tested liquid level gauge rises from 0 to full scale, and record the value measured by the tested liquid level gauge at each liquid level point during the rising process. The height value H _si and the height value h _si calculated by the standard device;

2.2 Open the discharge pipeline so that the liquid level in the liquid level gauge under test is reduced from full scale to 0, and record the height value H _xi measured by the liquid level gauge at each liquid level point and the standard value during the lowering process. The height value h _xi obtained by the device calculation;

2.3: Repeat step 2.1-step 2.2 at least once to obtain at least one new set of height value H _si measured by the liquid level gauge at each liquid level point value and the height value h calculated by the standard device when the liquid level rises _si , and when the liquid level drops, the height value H _xi measured by the tested liquid level gauge at each liquid level point and the height value h _xi calculated by the standard device;

Step 3: Based on multiple sets of H _si and h _si , H _xi and h _xi in step 2, calculate the indication error of each liquid level point value when the liquid level rises and falls when the liquid level is lowered for each measurement, and Calculate the average value of all indication errors at each liquid level point value to obtain the average value of indication value errors at each liquid level point value;

Step 4. Uncertainty analysis is performed on the average value of the indication error at each liquid level point value to obtain the expanded uncertainty of each liquid level point value of the tested liquid level gauge, and the The average value of the indication error and the expanded uncertainty are the calibration results of the tested liquid level gauge.

Further, in step 1, the way to obtain the liquid density ρ is:

If, described liquid is standard solution, then the density p of liquid is the density of standard solution;

If the liquid is not a standard solution, a certain amount of liquid is taken out and measured with a densitometer, and the density ρ of the liquid is the measured value of the densitometer.

Further, the standard solution is pure water, and the density ρ is known and fixed.

The beneficial effects of the present invention are:

1. The liquid level control assembly provided in the present invention is used to inject liquid into the liquid level gauge to be tested, and to control the liquid level of the liquid level gauge to be tested. When the liquid level of the liquid in the liquid level changes, the pressure on the lower end of the liquid level gauge under test, the second is to calculate the liquid level of the liquid in the liquid level gauge under test through the density of the liquid and the acceleration of gravity at the location, so that the liquid level of the liquid level gauge to be tested can be calculated The liquid level measured by the meter itself is compared with the accurate standard liquid level obtained by calculation, and after data processing, the calibration result of the tested liquid level meter is obtained, and the device proposed by the present invention is easy to carry, and can be used not only in the laboratory Calibration can also meet the needs of on-site measurement, which solves the problem of measurement error caused by transportation or the use of liquid level gauges in different environments from the laboratory, making the obtained calibration results more accurate than laboratory measurements. .

2. The scheme proposed by the present invention can not only carry out the calibration work of the pressure type liquid level gauge stipulated in the "JJG971-2019 Liquid Level Gauge Verification Regulations", but also has the ability to carry out communication type, buoyancy type, reflection type, electrical characteristic type, etc. On-site calibration of all liquid level gauges has strong versatility.

3. In the present invention, the digital pressure gauge is used to realize the input and display of external information, the calculation and display of the liquid level h in the liquid level gauge to be tested, and the data clearing function, which reduces the research and development cost of the entire device , suitable for large-scale promotion.

Description of drawings

Fig. 1 is the structural schematic diagram of the embodiment 1 of the present invention;

Fig. 2 is a schematic diagram of the structural principle of Embodiment 2 of the present invention;

In the figure, 1. Standard device; 2. Drainage pipeline; 3. Tank body; 4. First pipeline; 5. Second pipeline; 6. Pressure generator; 7. Third pipeline; 8. Density meter; 9, liquid level gauge.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Design idea of the present invention is:

Since it is inconvenient to use the designated equipment in the laboratory to calibrate the liquid level gauge 9 on site, in order to be portable, a liquid level gauge on-site calibration device is designed to realize the liquid level gauge by controlling the amount of liquid in the liquid level gauge 9. 9 internal pressure changes, then calculate the liquid level of the liquid level gauge 9 by the formula h=p/(ρg), then process the liquid level measured by the liquid level gauge 9 and the calculated liquid level to obtain the liquid level gauge 9 calibration results.

Based on the above-mentioned design ideas, when the liquid level gauge 9 is calibrated, the standard device 1 needs to be used. In the present invention, a digital pressure gauge with a high accuracy level (0.05 level and above accuracy level) after the transformation is selected as the standard device 1. Digital pressure gauges can measure pressure, but when calculating liquid levels, liquid density and gravity acceleration are also required. In order to save costs, it can be directly modified on existing high-accuracy digital pressure gauges, that is, digital pressure gauges The meter is equipped with a memory, a processor, and a computer program stored in the memory and that can run on the processor. When the processor executes the computer program, it realizes the pressure measurement and display function, realizes external information input and display, and realizes the liquid level gauge under test. Calculation and display of the liquid level h in 9, realizing the data clearing function, wherein the data includes pressure, external information and liquid level h, the external information includes liquid density ρ and the gravity acceleration g of the location, and the calculation formula of the liquid level h It is h=p/(ρg).

In order to ensure that the output of the digital pressure gauge has an overload prompt and ensure that the digital pressure gauge is not damaged by overload, the processor should also realize the display function of the pressure range usage when executing the computer program.

Example 1:

The present invention proposes an on-site calibration device for a liquid level gauge, as shown in Figure 1, comprising a liquid level control assembly, a digital pressure gauge, a drain line 2, and a third stop valve installed on the drain line 2;

Wherein, the liquid level control assembly includes a tank body 3, a first pipeline 4, a second pipeline 5, and two first shut-off valves respectively arranged on the first pipeline 4 and the second pipeline 5. Inside the tank body 3 Filled with liquid.

The specific connection method of each component is as follows:

The lower end of the tank body 3 communicates with one end of the second pipeline 5, the other end of the second pipeline 5 communicates with the lower end of the liquid level gauge 9 to be tested, the upper end of the tank body 3 communicates with one end of the first pipeline 4, and the first The other end of the pipeline 4 communicates with the upper end of the tested liquid level gauge 9, and the digital pressure gauge communicates with the lower end of the tested liquid level gauge 9 through the fourth pipeline. One end of the road 2 communicates with the lower end of the liquid level gauge 9 to be tested, and the other end connects with external equipment.

If the liquid meets the environmental safety requirements, the other end of the liquid discharge pipeline 2 can also be directly connected to the atmosphere for direct discharge.

If the tank body 3 is filled with a standard liquid, such as pure water, it is not necessary to carry a densitometer 8; if it is not a standard liquid, it is necessary to carry a densitometer 8 to measure the density of the liquid on site.

The selection method of the digital pressure gauge range is: according to the liquid level range of the tested liquid level gauge 9, combined with the density ρ of the liquid used for verification and the gravitational acceleration g on site, the tested liquid level gauge 9 can be deduced by the formula p=ρgh The required maximum pressure, which is 40%-70% of the full scale of the digital pressure gauge, can ensure that the uncertainty of the calibration result is small.

The accuracy level of the digital pressure gauge can be selected according to actual needs, and can be 0.05, 0.02 or 0.01.

The digital pressure gauge after the transformation can be traced back to the measurement standard of the digital pressure gauge before the transformation, and it should be carried out in accordance with the requirements of the digital pressure gauge verification regulations before the transformation to ensure the accuracy of its pressure output.

Example 2:

As shown in Figure 2, the difference between Embodiment 2 and Embodiment 1 lies in: the structure of the liquid level control assembly is different;

In this embodiment, the liquid level control assembly includes a pressure generator 6 and a third pipeline 7. One end of the third pipeline 7 communicates with the lower end of the liquid level gauge 9 to be tested, and the other end communicates with the pressure generator 6. The pressure generator The chamber of 6 is filled with liquid; the third pipeline 7 is provided with a second shut-off valve.

Based on the above-mentioned device, the present invention also proposes a method for obtaining the calibration result of the above-mentioned calibration device on-site, including the following steps:

Step 1: Obtain the density ρ of the liquid and the acceleration of gravity g in the area where the liquid level gauge 9 is located, and input the acceleration of gravity g and the density ρ of the liquid into the digital pressure gauge;

If the liquid is a standard solution, such as pure water, then the density ρ of the liquid is the density of the standard solution; if the liquid is not a standard solution, a certain amount of liquid is taken out and measured with a densitometer 8, and the density ρ of the liquid is The measured value of density meter 8;

The value of the acceleration of gravity g is selected in the appendix of the piston pressure gauge verification regulations, or measured on site;

Divide the range of the tested liquid level gauge 9 equally to obtain i liquid level point values, wherein, i≥3, that is, the range must be divided into at least two equal parts, for example, the liquid level gauge 9 with a range of 1m is divided Five equal parts, get 6 liquid level point values, respectively 0m, 0.2m, 0.4m, 0.6m, 0.8m, 1m;

Step 2: Data Measurement

2.1 Open the two first shut-off valves, the liquid in the tank 3 enters the liquid level gauge 9 to be tested, or open the second shut-off valve and the pressure generator 6, and the liquid in the chamber of the pressure builder 6 enters the liquid to be tested In the level gauge 9, the liquid level of the liquid in the tested liquid level gauge 9 rises from 0 to full scale, and the height value H _si measured by the tested liquid level gauge 9 at each liquid level point value is recorded during the rising process and the height value h _si calculated by the digital pressure gauge;

2.2 Open the third cut-off valve, so that the liquid level in the tested liquid level gauge 9 is reduced from full scale to 0, and record the height value H _xi measured by the tested liquid level gauge 9 at each liquid level point value during the lowering process and the height value h _xi calculated by the digital pressure gauge;

2.3: Repeat step 2.1-step 2.2 once to obtain a new set of height values H _si measured by the liquid level gauge 9 at each liquid level point value and the height value h calculated by the digital pressure gauge when the liquid level rises _si , and when the liquid level drops, the height value H _xi measured by the tested liquid level gauge 9 at each liquid level point and the height value h _xi calculated by the digital pressure gauge;

Step 3: Based on the two groups of H _si and h _si , H _xi and h _xi in step 2, calculate the indication error of each liquid level point value when the liquid level rises and falls when the liquid level is lowered for each measurement, and Calculate the average value of all indication errors at each liquid level point value to obtain the average value of indication value errors at each liquid level point value;

Step 4. Perform uncertainty analysis on the average value of the indication error at each liquid level point value to obtain the expanded uncertainty of the 9 liquid level point values of the tested liquid level gauge, and the 9 liquid level points of the tested liquid level gauge The average value of the indication error and the expanded uncertainty of the value are the calibration results of the tested liquid level gauge 9, wherein the expanded uncertainty of the tested liquid level gauge 9 can also be the maximum value of the expanded uncertainty of all liquid level point values ;

A calibration report is issued according to the calibration results, and the liquid level gauge can be selected for use each time according to the calibration report.

Claims (9)

1. A liquid level gauge field calibration device, characterized in that: Including liquid level control components, standard device (1) and drain line (2); The liquid level control assembly communicates with the tested liquid level gauge (9) and is used for injecting liquid into the tested liquid level gauge (9) and controlling the liquid level of the tested liquid level gauge (9); One end of the liquid discharge pipeline (2) communicates with the lower end of the tested liquid level gauge (9), and the other end communicates with external equipment, and is used to discharge the liquid in the tested liquid level gauge (9); The standard device (1) communicates with the lower end of the tested liquid level gauge (9), and is used to realize the measurement and display of the pressure on the bottom end of the tested liquid level gauge (9), realize the input and display of external information, and realize The calculation and display of the liquid level h of the liquid level gauge (9) to be tested, and the realization of the function of data clearing, wherein the data includes pressure, external information and liquid level h, and the external information includes liquid density ρ and gravitational acceleration g, The formula for calculating the liquid level h is h=p/(ρg). 2. A liquid level gauge field calibration device according to claim 1, characterized in that: The standard device (1) is a digital manometer; The digital manometer includes a memory, a processor, and a computer program stored in the memory and operable on the processor. When the processor executes the computer program, it realizes pressure measurement and display functions, and realizes external Information input and display, realize the calculation and display of the liquid level h of the tested liquid level gauge (9), and realize the function of data clearing, wherein the data includes pressure, external information and liquid level h, and the external information includes liquid density ρ and the gravitational acceleration g of the location, the calculation formula of the liquid level h is h=p/(ρg). 3. A liquid level gauge field calibration device according to claim 2, characterized in that: The liquid level control assembly includes a tank body (3), a first pipeline (4), a second pipeline (5) and two pipes respectively arranged on the first pipeline (4) and the second pipeline (5). a first stop valve; One end of the first pipeline (4) communicates with the upper end of the tank body (3), and the other end communicates with the upper end of the liquid level gauge (9) to be tested; One end of the second pipeline (5) communicates with the lower end of the tank body (3), and the other end communicates with the lower end of the liquid level gauge (9) to be tested; The tank body (3) is filled with liquid. 4. A liquid level gauge field calibration device according to claim 2, characterized in that: The liquid level control assembly includes a pressure generator (6), a third pipeline (7) and a second stop valve arranged on the third pipeline (7); One end of the third pipeline (7) communicates with the lower end of the tested liquid level gauge (9), and the other end communicates with the pressure generator (6); The chamber of the pressure builder (6) is filled with liquid. 5. A liquid level gauge field calibration device according to claim 3 or 4, characterized in that: It also includes a density meter (8) for measuring the density of the liquid in the tank (3) or the liquid in the chamber of the pressure builder (6). 6. A liquid level gauge field calibration device according to claim 5, characterized in that: When the processor executes the computer program, it can also realize the function of displaying the usage amount of the pressure range. 7. A method for obtaining a calibration result on-site for a liquid level gauge, characterized in that, adopting the on-site calibration device for a liquid level gauge according to any one of claims 1-6, comprising the following steps: Step 1: Obtain the density ρ of the liquid, the gravitational acceleration g of the region where the liquid level gauge (9) to be tested is used, and input the gravitational acceleration g and the density ρ of the liquid into the standard device (1); Divide the range of the tested liquid level gauge (9) equally to obtain i liquid level point values, wherein, i≥3, the first liquid level point value is 0, and the i-th liquid level point value is a full scale value; Step 2: Data Measurement 2.1 Inject liquid into the tested liquid level gauge (9), so that the liquid level in the tested liquid level gauge (9) rises from 0 to full scale, and record the value of each liquid level point during the rising process. The height value H _si measured by the liquid level gauge (9) and the height value h _si calculated by the standard device (1); 2.2 Open the drain line (2), so that the liquid level in the liquid level gauge (9) is reduced from full scale to 0, and record the value of each liquid level point in the liquid level gauge (9) during the lowering process. ) the height value H _xi measured and the height value h _xi calculated by the standard device (1); 2.3 Repeat steps 2.1-step 2.2 at least once to obtain at least one group of new liquid level rises, the height value H _si measured by the liquid level gauge (9) at each liquid level point value and the calculation of the standard device (1) The obtained height value h _si , and when the liquid level drops, the height value H _xi measured by the liquid level gauge (9) at each liquid level point and the height value h _xi calculated by the standard device (1); Step 3: Based on multiple sets of H _si and h _si , H _xi and h _xi in step 2, calculate the indication error of each liquid level point value when the liquid level rises and falls when the liquid level is lowered for each measurement, and Calculate the average value of all indication errors at each liquid level point value to obtain the average value of indication value errors at each liquid level point value; Step 4. Perform uncertainty analysis on the average value of the indication error at each liquid level point value, and obtain the expanded uncertainty of each liquid level point value of the tested liquid level gauge (9), and the tested liquid level gauge (9) The average value of the indication error and the expanded uncertainty of each liquid level point value are the calibration results of the tested liquid level gauge (9). 8. The method for obtaining calibration results on-site of a liquid level gauge according to claim 7, characterized in that: In step 1, the way to obtain liquid density ρ is: If, described liquid is standard solution, then the density p of liquid is the density of standard solution; If the liquid is not a standard solution, a certain amount of liquid is taken out and measured with a densitometer (8), and the density ρ of the liquid is the measured value of the densitometer (8). 9. The method for obtaining calibration results on-site for a liquid level gauge according to claim 8, characterized in that: The standard solution is pure water, and the density ρ is a known fixed value.

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