CN106643989B - Density calibration system and method for mass flowmeter - Google Patents

Abstract

The application provides a density calibration system and a method of a mass flowmeter, wherein the system comprises the following components: calibration solution means for providing a plurality of calibration solutions having different densities; a solution pump for providing power to flow the calibration solution at a pressure within the calibration tubing; the standard meter and the mass flow meters to be measured are uniformly arranged on the calibration pipeline along the output end of the solution pump; the standard table is used for calibrating the density of the calibrating solution in the pipeline; the computer is respectively connected with a plurality of mass flowmeters to be tested, a standard meter and a switch; the method is used for controlling the switch to switch the calibration solutions of different media to calibrate the density of the mass flowmeter, and the calculated density calibration coefficient is written into the corresponding mass flowmeter according to a density calibration mathematical model. The density of the mass flowmeter is measured for many times by adopting the calibration solution of the computer in different mediums, and the density of the mass flowmeter to be measured is calculated through a density calibration mathematical model, so that the calibration efficiency and precision are improved.

Description

Density calibration system and method for mass flow meter

Technical field

The invention belongs to the technical field of instrument calibration, and in particular relates to a density calibration system and method for a mass flow meter.

Background technique

Mass flow meter, also known as Coriolis force mass flow meter, is a flow measurement instrument developed and designed using the principles of fluid mechanics. It is mainly used to measure the mass flow and density of gases and liquids, as well as the parameters required for engineering such as volume flow, total mass, and total volume derived from mass flow and density. The mass flow meter can measure a wide range of fluids, including various liquids with high viscosity, slurries containing solids, liquids containing a small amount of evenly distributed gas, and gases with sufficient density, such as high-pressure gases. Overall, it is capable of measuring mass flow, density and temperature of liquids, suspensions, emulsions and gases.

Regarding the establishment and implementation of the mass flow mathematical model of the mass flow meter, as well as the calibration process in production, there are a lot of explanations in many papers, journals and patents at home and abroad. There are countless parameter methods available, but in terms of density There are not many literatures available for reference on the mathematical model and calibration methods and related calibration equipment. For mass flow meters, the first parameter is mass flow, and the parameter related to it and corresponding to the proportional output is the phase difference of the sinusoidal signal detected and output on both sides of the sensor measurement tube; the second parameter is density, which is related to the inherent mechanical properties of the sensor itself. Frequency-related, only with the existence of the second parameter density, there will be engineering parameters such as volume flow and total volume derived from mass flow and density. Therefore, mass is used when measuring parameters such as mass flow, density, and volume flow of various conventional fluids, unconventional fluids, slurries, liquefied gases, and compressed natural gas in many fields such as petroleum, petrochemicals, papermaking, food, and pharmaceuticals. flow meter. Therefore, it is crucial for manufacturers of mass flow meters to improve the design, production and processing technology of mass flow meter sensors, as well as mass flow calibration devices and density calibration devices.

As shown in Figure 1, it is a schematic structural diagram of the existing Coriolis force mass flow meter density calibration system. Among them, the low pressure cylinder is used to store low-pressure dry air with a pressure of less than 5 atmospheres; the air valve is used to The switch used to control the low-pressure gas in the low-pressure cylinder entering the calibration pipeline; the calibration solution container, which is used to hold the medium solution for density calibration, and the calibration solution is usually proportioned in this container; the solution inlet end, which is the density calibration solution The starting end is designed as a funnel, which facilitates the calibration solution to flow into the sensor measurement pipe through this port without side leakage; the calibration pipe is used to calibrate the channel through which the medium solution flows; the mass flow meter is the mass to be density calibrated Flowmeter; fixed base frame, which is a cement pile, used to fix the mass flowmeter to be calibrated; solution outlet end, which is the end of the density calibration pipeline, is designed as a funnel to facilitate the calibration solution to flow into the measurement through this port in a volume container; a switch, which is used to control the amount of density calibration solution flowing into the volume container; a volume container, which is used to hold the density calibration medium solution and measure the volume of the density calibration solution at the same time; an electronic scale, which is used to The mass of the density calibration solution in the measuring volume container.

The calibration method flow of the density calibration system of the mass flow meter in Figure 1 is detailed as follows:

Step 1: Place the mass flow meter density calibration system in a constant temperature chamber at 25°C. At the same time, keep the gas valve and the switches at the end of the calibration pipeline closed;

Step 2. Install the mass flow meter to be measured on the calibration pipeline as shown in Figure 1, and ensure that the calibration pipeline and the mass flow meter installation flange are in a sealed state, that is, there is no leakage, and at the same time, the mass flow rate is guaranteed. The meter housing is vertical to the ground;

Step 3: Power on the mass flowmeter to be calibrated, and at the same time place more than 5 calibration solutions with different densities (medium solution 1, medium solution 2, medium solution 3...) in the secret room used for density calibration. , keep working in this state for about 180 minutes. The purpose is to make the temperature of the entire mass flow meter density calibration system and the density calibration solution the same as or infinitely close to the temperature of the chamber;

Step 4: Collect the empty pipe frequency of the output sensor of the mass flow meter converter on the currently calibrated pipeline in the constant temperature chamber at 25°C to be density calibrated;

Step 5: Open the sealing cover on the solution inlet end, slowly pour the density calibration medium solution 1 into the solution inlet end through the calibration solution container device, observe the changes in the liquid level at the solution outlet end, and stop when the liquid level is close to the top of the solution outlet end. Continue to pour density calibration medium solution 1 into the inlet end of the solution;

Step 6: Delay for 2 minutes until the density calibration medium solution 1 is in a stable state in the calibration pipeline device, and collect the frequency value of the output sensor on the current mass flow meter converter;

Step 7: Slowly adjust the switch at the end of the calibration pipeline to discharge the density calibration medium solution 1 in the pipeline into the container at the upper end of the electronic scale, so that the discharge volume of the density calibration medium solution 1 reaches the 1000ml mark of the container;

Step 8: Obtain the mass indication of measuring 1000ml of density calibration medium solution 1 on the electronic scale, pour the density calibration medium solution 1 back into the original solution device, and replace it with a dry container of the same capacity and place it on the electronic scale;

Step 9: Press the sealing cap above the solution inlet end tightly against the solution inlet end, slowly adjust the air valve until the density calibration medium solution 1 in the calibration pipe is driven out of the calibration pipe, and close the air valve;

Step 10: Repeat steps 5 to 9 to complete the calibration process of other density calibration medium solutions (medium solution 2, medium solution 3...);

Step 11, based on the density calibration record data, calculate the density coefficient of the mass flow meter to be density calibrated, and write the coefficient into the EEPROM of the mass flow meter converter through key operation;

Step 12: Perform density accuracy and repeatability testing of the mass flow meter;

Step 13. Open the sealing cover on the solution inlet end and the switch at the end of the calibration pipe. Slowly pour the density calibration medium solution 1 into the solution inlet end through the calibration solution container device. Observe the change of the liquid level in the container. When the liquid level scale When it is close to 1000ml, turn off the switch at the end of the calibration pipeline and continue to pour an appropriate amount of density calibration medium solution 1 into the solution inlet end;

Step 14: Fine-tune the opening of the switch at the end of the calibration pipeline until the drop value of the density calibration medium solution 1 in the container reaches the 1000ml scale position. Collect the current output density value of the mass flow meter converter and the electronic scale to measure the density calibration medium solution 1. total mass;

Step 15: Press the sealing cap above the solution inlet end tightly against the solution inlet end, fine-tune the air valve until the density calibration medium solution 1 in the calibration pipe is driven out of the calibration pipe, and close the air valve;

Step 16: Repeat steps 13 to 15 to complete the density calibration process for other selected density calibration medium solutions;

Step 17: Calculate the density output accuracy and repeatability of the mass flow meter.

The existing Coriolis force mass flow meter density calibration system can only accommodate the density calibration and detection of up to three mass flow meters, which greatly reduces the calibration efficiency of the mass flow meter; at the same time, in the entire calibration and detection process In the process, manual participation is required, and the density of the calibration solution is measured in a small container. An electronic scale measures the mass of the calibration solution, and the density standard value of the calibration solution is determined through calculation. However, these factors will bring a certain degree of measurement calibration error and reduce the accuracy of the entire mass flow meter density calibration system.

Contents of the invention

In view of the above shortcomings of the prior art, the purpose of the present invention is to provide a density calibration system and method for a mass flow meter to solve the problem that manual operation is required during density calibration of the mass flow meter in the prior art, resulting in the entire mass flow rate The problem of low efficiency and low accuracy of density meter calibration.

In order to achieve the above objects and other related objects, the present invention provides a density calibration system for mass flow meters, including:

Calibration solution device, which is used to provide a variety of calibration solutions with different densities;

Solution pump, which is used to provide power to flow the calibration solution in the calibration pipeline at a certain pressure;

A standard meter and multiple mass flow meters to be measured are evenly installed on the calibration pipeline along the output end of the solution pump;

The standard table is used to calibrate the density of the calibration solution in the calibration pipeline;

A computer, which is respectively connected to multiple mass flow meters, standard tables and switches to be measured; which is used to control the switch to switch calibration solutions of different media to calibrate the density of the mass flow meter, and calculate the calculated density according to the density calibration mathematical model The calibration coefficient is written into the corresponding mass flow meter.

The object of the present invention is also to provide a density calibration method for a mass flow meter, which includes:

Step 1: Initialize the density calibration system to ensure that the mass flow meter to be measured tends to a stable state;

Step 2: When the mass flow meter is in the empty pipe state, read the frequency value output by the mass flow meter to be measured in sequence;

Step 3: Turn on the switch of a certain medium calibration solution device and the switch close to the standard meter, so that the calibration solution of that medium circulates in the calibration pipeline until there are no bubbles in the calibration solution flowing in the mass flow meter to be measured;

Step 4: Turn off the switch of the calibration solution device and the switch near the standard meter until the calibration solution in the calibration pipeline is in a static state;

Step 5: Read the current density value of the standard table, and read the frequency value output by the mass flow meter to be measured in sequence;

Step 6: Repeat steps 3 to 5 under the calibration solutions of different media to obtain the density value of the standard table and the frequency value output by the mass flow meter to be measured;

Step 7: Call the density calibration mathematical model to calculate the density coefficient of each mass flow meter to be measured in sequence, and write it into the corresponding mass flow meter to be measured;

Step 8: Repeat steps 3 to 4 multiple times under each medium calibration solution to obtain the multiple calibration standard density values of the standard table and the multiple output density values of the mass flow meter to be measured;

Step 9: Calculate the accuracy of the mass flow meter based on the corresponding standard density values in various medium calibration solutions and the density value output by the mass flow meter.

As mentioned above, the density calibration system and method of the mass flow meter of the present invention have the following beneficial effects:

By replacing the original manually operated density calibration system with a computer-automated density calibration system, the number of calibration units per time has been changed from three to ten compared to the original density calibration system, which improves the efficiency of product calibration; the use of computers The control switch switches between calibration solutions in different media, and the density of the mass flow meter is measured multiple times under each calibration solution. There is no need for human participation in the calibration process. The density of the mass flow meter to be measured is calculated through the density calibration mathematical model, which not only eliminates The calibration error of the traditional mass volume method also greatly improves the accuracy of the mass flow meter density calibration; at the same time, a constant pressure and constant flow tank is introduced into the density calibration system, which eliminates the calibration solution trickle produced by the solution pump when it is working. The problem of flow and air bubbles essentially improves the calibration accuracy of the mass flow meter.

Description of the drawings

Figure 1 shows a schematic structural diagram of an existing Coriolis force mass flowmeter calibration system provided by the present invention;

Figure 2 shows the structure diagram of the density calibration system of a mass flow meter provided by the present invention;

Figure 3 shows a structural diagram of an embodiment of a density calibration system for a mass flow meter provided by the present invention;

Figure 4 shows a flow chart of a density calibration method for a mass flow meter provided by the present invention.

Detailed ways

The implementation of the present invention is described below with specific embodiments. Those familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

See Figure 2 to Figure 4. It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to this specification are only used to coordinate with the content disclosed in the specification for the understanding and reading of those familiar with this technology, and are not used to limit the implementation of the present invention. Restrictive conditions, so they have no technical substantive significance. Any structural modifications, changes in proportions, or adjustments in size should still fall within the scope of the present invention as long as they do not affect the effects that the present invention can produce and the purposes that can be achieved. The technical content disclosed must be within the scope that can be covered. At the same time, terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for convenience of description and are not used to limit the scope of this specification. The scope of the invention that can be implemented, and changes or adjustments in their relative relationships, as long as there is no substantial change in the technical content, shall also be regarded as the scope of the invention that can be implemented.

Please refer to Figure 2. The present invention provides a structural diagram of a density calibration system for a mass flow meter, including:

Calibration solution device 1, which is used to provide a variety of calibration solutions with different densities; solution pump 3, which is used to provide power to flow the calibration solution in the calibration pipeline at a certain pressure; standard table 4 and multiple mass flow meters to be measured 5 is evenly installed on the calibration pipeline along the output end of the solution pump 3; the standard table 4 is used to calibrate the density of the solution in the calibration pipeline; the computer 6 is connected to multiple mass flow meters to be measured 5, Standard table 4 and switch 3; it is used to control the switch 3 to switch calibration solutions of different media to calibrate the density of the mass flow meter 5, and write the calculated density calibration coefficient into the corresponding mass flow meter 5 according to the density calibration mathematical model. .

Among them, the computer 6 can be replaced by an industrial computer or terminal, and there can be multiple calibration solution devices 1. Each calibration solution device 1 contains a calibration solution with the same medium density; and the calibration solution device 1, the solution pump 3, and the standard meter 4. The mass flow meters 5 are connected to each other using calibration pipelines; and a switch 2 is provided on the calibration pipeline between the output end of each calibration solution device 1 and the solution pump 3, and the input end of each calibration solution device 1 A switch 2 is provided on the connected calibration pipelines. The switch 2 here ensures that only one medium calibration solution flows in the calibration pipeline in the density calibration system at a time.

A switch for controlling the flow of the calibration solution is provided between the solution pump 3 and the standard table 4, and setting the corresponding switch 2 here can ensure that the solution pump 3 flows the calibration solution to the standard table 4 through its own power, and at the same time , when the switch is closed, the continuous operation of the solution pump can displace the air bubbles existing in the calibration pipeline. The switch 2 is a valve, a gate and a solenoid valve, preferably a solenoid valve, which can be directly controlled by the computer 6 and through the computer 6. Remotely control the switching of calibration solutions in different media, and measure the density of the mass flow meter 5 multiple times under each calibration solution. There is no need for human participation in the calibration process. The density of the mass flow meter 5 to be measured is calculated through the density calibration mathematical model. It not only eliminates the calibration error of the traditional mass volume method, but also greatly improves the accuracy of the density calibration of the mass flow meter.

If there are requirements for the pressure and flow rate of the calibration solution in the density calibration system, a constant pressure and constant flow tank for stable flow and pressure can be provided between the solution pump 3 and the switch 2 close to the standard table 4. By opening the constant pressure The exhaust switch on the constant flow tank device will be closed until the calibration solution supplied by the solution pump 3 fills the constant pressure constant flow tank to the maximum extent. The purpose is to eliminate the air bubbles in the calibration solution and the non-constant pressure of the calibration solution. In the state of constant current, if you want to set up a constant pressure and constant current tank here, it must be connected to the computer via the control bus to achieve automatic control.

In this application, the computer 6 uses a control bus to communicate with multiple mass flow meters 5, standard tables 4 and switches 2 to be measured. The computer sends instructions to control the opening and closing of the switch 2, and collects the standard table 4 and the mass flow meter. The data of the flow meter 5 is used to calculate the density value and accuracy of each mass flow meter 5 to be tested according to the density calibration mathematical model. Among them, the number of mass flow meters 5 to be tested is at most ten. Compared with the original method, which can only calibrate at most three at the same time, the calibration efficiency is improved.

In this application, the density calibration mathematical model is as follows:

In formula (1), ρ: density of mass flowmeter calibration measurement medium solution, unit kg/M ³ ; K _d : density coefficient of calibration calculation output, dimensionless; F _e (25): mass flow meter sensor at constant temperature 25 The resonant frequency of the measuring tube at ℃ temperature, unit Hz; F _kt : the correction coefficient related to the material, structure and temperature of the mass flow meter sensor, usually the change in the resonant frequency of the sensor measuring tube for every increase or decrease of 1°C ;T: mass flowmeter sensor temperature; F _r : the actual output frequency of the mass flow meter sensor when the measuring pipe is filled with metering medium solution, unit Hz; when K _d is calculated, the mass flow rate is calculated based on the read F _r Calculate the density of the calibrated medium solution.

It also includes a fixed frame, which is arranged on both sides of the mass flow meter 5 and the standard meter 4 to support their work. The fixed frame is preferably a cement bracket, which can not only eliminate the vibration of the pipeline but also treat the density calibration mass flow meter. The influence of the instrument can also eliminate the influence of the mechanical vibration of the mass flow meter 5 sensor itself on the density calibration. At the same time, the fixed frame also plays a role in isolating the mass flow meters 5 to be calibrated online to prevent mutual influence between the mass flow meters 5 to be calibrated.

As shown in Figure 3, it is a structural diagram of an embodiment of a density calibration system for a mass flow meter provided by the present invention; including:

In this embodiment, the number of mass flow meters 5 to be density calibrated is ten. The standard meter 4 and the ten mass flow meters 5 are respectively installed in the calibration pipeline from left to right along the output direction of the solution pump 3. On both sides of the mass flow meter 5 and the standard meter 4 are fixed frames to support their work. The medium solution device 1 is divided into five calibration solutions containing different media respectively. Among them, the first to fifth solenoid valves are respectively installed on the calibration pipes at the output ends of the first to fifth medium solution devices 1. The first to fifth solenoid valves are installed respectively. The calibration pipes at the input end of the medium solution device 1 are respectively installed with sixth to tenth solenoid valves, and the calibration pipes output by the tenth mass flow meter 5 (i.e. the rightmost mass flow meter 5) are connected to each medium solution. The input end of the device 1, so that the calibration solution of each medium can circulate in the calibration pipeline and then return to the medium solution device 1. The eleventh solenoid valve is installed on the calibration pipeline between the solution pump 3 and the standard table 4. .

The computer 6 is respectively connected to the standard meter 4, multiple mass flow meters 5 and multiple solenoid valves through a control bus, and switches the calibration solution of each medium by controlling the solenoid valve switch. For example, when the eleventh solenoid valve is opened, The medium solution device 1 that needs to contain the calibration solution of a certain medium opens its solenoid valve and closes other solenoid valves so that the calibration solution of the medium flows to the entire density calibration system. When the calibration solution of the medium has no bubbles in the calibration pipeline And when in a static state, read the output frequency of the mass flow meter to be measured in sequence; calculate the density coefficient of each mass flow meter to be measured through the density calibration mathematical model, and then repeat the above steps to obtain one or more In the case of a medium solution, the density of each mass flow meter 5 to be measured is used to calculate the accuracy of the corresponding mass flow meter based on the density of the mass flow meter 5 to be measured.

Please refer to Figure 4, which is a density calibration method of a mass flow meter provided by the present invention, including:

Step 1: Initialize the density calibration system to ensure that the mass flow meter to be measured tends to a stable state;

Specifically, during the initialization process of the density calibration system, the computer controls all switches to be closed, and the mass flow meter to be measured is installed in the calibration pipeline to ensure that the mass flow meter is in a sealed state, that is, there is no leakage; the standard table and the mass flow rate The meter is powered on, and the computer connects the standard meter, mass flow meter and solenoid valve through bus control; for example, a delay of several minutes is generally used to allow the mass flow meter to be calibrated to work in the empty state of the calibration pipeline or to stabilize. state.

Step 2: When the mass flow meter is in the empty pipe state, read the frequency value output by the mass flow meter to be measured in sequence;

Step 3: Turn on the switch of a certain medium calibration solution device and the switch close to the standard meter, so that the calibration solution of that medium circulates in the calibration pipeline until there are no bubbles in the calibration solution flowing in the mass flow meter to be measured;

Step 4: Turn off the switch of the calibration solution device and the switch near the standard meter until the calibration solution in the calibration pipeline is in a static state;

Step 5: Read the current density value of the standard table, and read the frequency value output by the mass flow meter to be measured in sequence;

Step 6: Repeat steps 3 to 5 under the calibration solutions of different media to obtain the density value of the standard table and the frequency value output by the mass flow meter to be measured;

Step 7: Call the density calibration mathematical model to calculate the density coefficient of each mass flow meter to be measured in sequence, and write it into the corresponding mass flow meter to be measured;

Step 8: Repeat steps 3 to 4 multiple times under each medium calibration solution to obtain the multiple calibration standard density values of the standard table and the multiple output density values of the mass flow meter to be measured;

Step 9: Calculate the accuracy of the mass flow meter based on the corresponding standard density values in various medium calibration solutions and the density value output by the mass flow meter.

In this embodiment, the following process can be obtained by expanding the above method process, which is detailed as follows:

1. Open the mass flow meter density calibration system software in the industrial computer (computer) and close all solenoid valves in the entire calibration system;

2. Install the mass flowmeter instruments to be density calibrated on the calibration pipeline in order from front to back (along the output direction of the solution pump, that is, the distance close to the solution pump is the front, and the distance away from the solution pump is the back) to ensure no leakage. state;

3. Power on and initialize the mass flow rate and standard table to be calibrated, and the communication bus is connected to the bus communication interface of the industrial computer;

4. Carry out communication detection of the mass flow rate and standard meter to be calibrated to ensure that each online mass flow rate and standard meter communicates normally with the mass flow meter density calibration system software in the industrial computer;

5. Trigger the mass flow meter density calibration system in the industrial computer and start the online mass flow meter density calibration process;

6. Delay for about 3 minutes so that the mass flow rate to be calibrated online is in or tends to a stable working state when the pipe is empty;

7. According to the numbering sequence from front to back, sequentially collect the frequency data of the mass flow rate in the empty pipe state for online density calibration;

8. Open the first solenoid valve, the sixth solenoid valve and the eleventh solenoid valve on the calibration pipeline through the control bus, while other solenoid valves are closed;

9. Driven by the solution pump, the medium solution in the first medium solution device flows through the calibration pipe, the standard meter, and the online mass flow meter to be calibrated for density. After circulation, it flows back to the first medium solution device through the calibration pipe. Delay work in this state for a few (five) minutes until the entire calibration pipeline and the measuring tube of the mass flow meter to be calibrated online are completely filled with the medium solution in the first medium solution device without bubbles;

10. Close the first solenoid valve, the sixth solenoid valve and the eleventh solenoid valve on the calibration pipeline through the control bus until the density calibration medium solution in the entire calibration pipeline is calm and has no flow. For example, a delay of 1 minute can be used. Achieve a calm and flow-free state;

11. Read the standard density value currently output by the standard table through the bus, read the mass flow rate to be calibrated online in order of number, and output the frequency value in this state;

12. Repeat steps 8)-11) to complete the density calibration process of the medium solution in the second to fifth medium solution devices; the only difference is that the solenoid valves controlled are different, as follows:

The second solenoid valve, the seventh solenoid valve, and the eleventh solenoid valve need to be controlled for density calibration of the second medium solution device;

The third solenoid valve, the eighth solenoid valve, and the eleventh solenoid valve need to be controlled for density calibration of the third medium solution device;

The fourth solenoid valve, the ninth solenoid valve, and the eleventh solenoid valve need to be controlled for density calibration of the fourth medium solution device;

The fifth solenoid valve, the tenth solenoid valve, and the eleventh solenoid valve need to be controlled for density calibration of the fifth medium solution device;

13. Based on the density calibration mathematical model of the internal package, calculate the density coefficient of each mass flow meter in sequence, and write the density coefficient into the online mass flow meter converter in sequence;

14. Repeated testing and calculation of the density output accuracy of the online mass flow meter;

15. Open the first solenoid valve, the sixth solenoid valve and the eleventh solenoid valve on the calibration pipeline through the control bus, while other solenoid valves are closed;

16. Driven by the solution pump, the medium solution in the first medium solution device flows through the calibration pipe, the standard meter, and the online mass flow meter to be calibrated for density. After circulation, it flows back to the first medium solution device through the calibration pipe. Delay work in this state for a few (five) minutes until the entire calibration pipeline and the measuring tube of the mass flow meter to be calibrated online are completely filled with the medium solution in the first medium solution device without bubbles;

17. Close the first solenoid valve, the sixth solenoid valve and the eleventh solenoid valve on the calibration pipeline through the control bus until the density calibration medium solution in the entire calibration pipeline is calm and has no flow. For example, a delay of 1 minute can be used. Achieve a calm and flow-free state;

18. Read the standard density value output by the standard meter through the bus, read the density value output by the online mass flow rate to be calibrated in this state from front to back, and calculate the accuracy of the mass flow meter;

19. Repeat steps 15)-18) to detect the density of the medium solution in the first medium solution device for the second time;

20. The mass flow meter density calibration system software repeats steps 15)-18), detects the density of the medium solution in the first medium solution device for the third time, and calculates the repeatability of the online mass flow meter density output in sequence;

21. Repeat steps 15)-20) to complete the verification of the density output and repeatability of the medium solution in the second to fifth medium solution devices;

22. Report the online mass flow meter density calibration and testing results (accuracy and repeatability) to the production user.

In summary, the present invention replaces the original manually operated density calibration system with a computer-automated density calibration system. Compared with the original density calibration system, the number of calibrations per time is changed from three to ten, thus improving product quality. The efficiency of the calibration; a computer-controlled switch is used to switch calibration solutions in different media, and the density of the mass flow meter is measured multiple times under each calibration solution. There is no need for human participation in the calibration process. The mass flow rate to be measured is calculated through the mathematical model of density calibration. The density of the meter not only eliminates the calibration error of the traditional mass volume method, but also greatly improves the accuracy of the density calibration of the mass flow meter. At the same time, a constant pressure and constant flow tank is introduced into the density calibration system, which eliminates the problem of the solution pump working. This eliminates the problems of calibration solution trickle and air bubbles, which essentially improves the calibration accuracy of the mass flow meter. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present invention shall still be covered by the claims of the present invention.

Claims (7)

1. A density calibration system for a mass flow meter, comprising:

the device comprises a plurality of calibration solution devices, a plurality of liquid crystal display devices and a plurality of liquid crystal display devices, wherein the plurality of calibration solution devices are used for providing a plurality of calibration solutions with different densities, each calibration solution device contains the calibration solution with the same density, a switch is arranged on a calibration pipeline between the output end of each calibration solution device and a solution pump, and a switch is arranged on the calibration pipeline connected with the input end of each calibration solution device;

a solution pump for providing power to flow the calibration solution at a pressure within the calibration tubing;

the standard meter and the mass flow meters to be measured are uniformly arranged on the calibration pipeline along the output end of the solution pump;

the standard table is used for calibrating the density of the calibrating solution in the pipeline; a constant-pressure constant-current tank for stabilizing current and voltage is arranged between the solution pump and a switch close to the standard meter;

the computer is respectively connected with a plurality of mass flowmeters to be tested, a standard meter and a switch; the method is used for controlling the switch to switch the calibration solutions of different media to calibrate the density of the mass flowmeter, and the calculated density calibration coefficient is written into the corresponding mass flowmeter according to a density calibration mathematical model.

2. The mass flowmeter density calibration system of claim 1, wherein a switch for controlling the flow of the calibration solution is provided between the solution pump and the standard meter.

3. The mass flow meter density calibration system of claim 2, wherein the switch is a solenoid valve.

4. The mass flowmeter density calibration system of claim 1, wherein the computer communicates with the mass flowmeter to be measured, the standard meter and the switch using a control bus.

5. The mass flowmeter density calibration system of claim 1, further comprising a stationary frame disposed on either side of the mass flowmeter and standard meter for supporting operation thereof.

6. The mass flowmeter density calibration system of claim 1, wherein the number of mass flowmeters to be measured is at most ten.

7. A method for calibrating density of a mass flowmeter, comprising:

step 1, initializing a density calibration system, and ensuring that a mass flowmeter to be tested tends to be in a stable state;

step 2, sequentially reading the frequency value output by the mass flowmeter to be tested when the mass flowmeter is in the empty pipe state;

step 3, a switch of a certain medium calibration solution device and a switch close to a standard meter are started, so that the calibration solution of the medium circularly flows in a calibration pipeline until the calibration solution flowing in the mass flowmeter to be tested has no bubbles;

step 4, closing a switch of the calibration solution device and a switch close to the standard meter until the calibration solution in the calibration pipeline is in a static state;

step 5, reading the current density value of the standard meter, and sequentially reading the frequency value output by the mass flowmeter to be tested;

step 6, repeating the steps 3 to 5 under the calibration solutions of different mediums to obtain the density value of the standard meter and the frequency value output by the mass flowmeter to be tested;

step 7, calling a density calibration mathematical model to sequentially calculate the density coefficient of each mass flowmeter to be measured, and writing the density coefficient into the corresponding mass flowmeter to be measured;

step 8, repeating the steps 3 to 4 for a plurality of times under each medium calibration solution to obtain a standard density value of a standard meter for a plurality of times calibration and a density value of a mass flowmeter to be tested for a plurality of times output;

and 9, calculating the precision of the mass flowmeter according to the standard density values corresponding to the various medium calibration solutions and the density values output by the mass flowmeter.