Multi-channel micro-gas automatic metering device and metering method

Abstract

The application discloses a kind of multi-channel trace gas automatic metering device and metering method, belong to gas flow measurement field, solve multi-channel trace gas detection difficult, insufficient precision, low automation degree and other problems.The device includes multiple sets of gas collection water column unit, cantilever type rotatable metering unit, device shell, limit switch, temperature sensor, reversing electromagnetic valve and control unit;Gas collection water column unit is combined with gas collection bag and water column to form gas-water separation structure, and cantilever type metering unit is rotated by gap driven non-contact liquid level sensor by stepper motor.When metering, scanning parameters are set first, and limit switch positioning sensor is used to scan each water column water level in turn, and reversing electromagnetic valve realizes gas path switching, combined with temperature compensation, exhaust volume and rate are calculated according to the number of electromagnetic valve actions and water level change.The device can be continuously and efficiently metered in multiple channels, and is convenient to disassemble and expand, has water level, motor abnormal alarm function, can automatically collect, store and display data, reduces labor cost and improves metering accuracy.

Description

Technical Field

[0001] This invention belongs to the field of gas flow measurement, and in particular relates to an automatic metering and metering method suitable for multi-channel micro-gas flow. Background Technology

[0002] In engineering and laboratory settings, there are various scenarios requiring the measurement of trace gas flow rates, such as metabolic rate determination in bioreactors, material balance calculations in small-scale composting devices, and analysis of exhaust gas flow rates at the anode and cathode of microbial fuel cells. These scenarios are characterized by small exhaust flow rates, long cycles, high detection frequency, and a large workload for gas flow measurement. In particular, research involving small exhaust volumes, multiple groups, and numerous parallel experiments requires frequent and simultaneous detection of gas flow rates from multiple exhaust devices.

[0003] Currently, laboratories still primarily rely on manual methods to test and record exhaust volumes. However, for long-cycle exhaust processes, manual measurement is extremely time-consuming and labor-intensive. Existing patents for trace gas metering devices are mainly single-channel. The trace gas flow meter described in the patent "Trace Gas Flow Meter and Flow Measurement Method" (application publication number CN103076054) mainly includes a fixed chamber, a weighing chamber, a weighing sensor, and a gas pump. It calculates the flow rate of trace gases by measuring the change in liquid volume caused by gas changes and measuring the weight change in the weighing chamber using the weighing sensor. However, this device is unsuitable for the rapid and efficient detection of gas flow rates in large-scale exhaust systems. Therefore, it is necessary to propose an automatic trace gas metering device suitable for multi-channel exhaust systems to address the difficulties in detecting multiple exhaust channels, insufficient metering accuracy, low automation, and the challenge of real-time monitoring. Summary of the Invention

[0004] In view of the shortcomings of the prior art, this invention proposes a multi-channel micro-volume automatic metering device and metering method that is easy to operate and has high metering efficiency.

[0005] One of the above-mentioned objectives of the present invention is achieved by the following technical solution: A multi-channel micro-volume automatic metering device includes multiple sets of gas collecting water column units, a cantilevered rotatable metering unit, a device housing, a starting limit switch, an ending limit switch, a temperature sensor, a reversing solenoid valve, and a control unit. Each gas collecting water column unit adopts a columnar unit that can store water column at the top and collect gas at the bottom; multiple gas collecting water column units are placed in multiple placement holes evenly distributed around the center of the device housing; the lower part of each gas collecting water column unit is equipped with a reversing solenoid valve to realize the exhaust input of a channel exhaust device, and each is equipped with another reversing solenoid valve to realize the exhaust of gas in the gas collecting water column unit. The cantilevered rotatable metering unit is installed on the device housing, and the rotation center of the cantilever coincides with the center of the housing. A non-contact liquid level sensor is installed at the end of the cantilever that is away from its rotation center. The non-contact liquid level sensor is located above the gas collecting water column unit. The starting limit switch and the ending limit switch are installed inside the device housing, along the circumferential arrangement direction of multiple sets of gas collecting water column units. The starting limit switch is set on the outer side of the first set of gas collecting water column units in a radially facing position, and the ending limit switch is set on the outer side of the last set of gas collecting water column units at a offset position. The temperature sensor is mounted on the device housing and is used to measure the ambient temperature and for temperature compensation in gas volume calculation. The control unit uses a microcontroller to control the opening and closing of the multi-channel air passages corresponding to multiple sets of gas collecting water column units and the switching control of air intake and exhaust for each air passage. It also controls the cantilevered rotatable metering unit to scan and detect the water column level and water level changes of the multiple gas collecting water column units in an intermittent rotational motion, and stores the detected data and scanning frequency data.

[0006] Furthermore, the gas collecting water column unit includes a tubular container, a gas collecting bag, and a sealing plug. The tubular container is open at both the top and bottom. The body of the gas collecting bag is placed inside the tubular container with its opening facing downwards. The sealing plug is inserted into the lower opening of the gas collecting bag and is sealed and fixed to the inner wall of the lower end of the tubular container. A sealed gas collecting space is formed inside the gas collecting bag, and a water column receiving cavity is formed above the gas collecting bag inside the tubular container. Two short connecting pipes are fixedly inserted through the sealing plug, namely an inlet pipe and an outlet pipe. The inlet pipe is connected to the inlet pipeline through a reversing solenoid valve to allow the gas discharged from the fermenter to enter the gas collecting bag. The outlet pipe is connected to the outlet pipeline through another reversing solenoid valve to allow the gas from the gas collecting bag to be discharged into the surrounding atmosphere.

[0007] Furthermore, the top of the tubular container is equipped with a cap, and a sensor probe detection hole is left in the middle of the cap.

[0008] Furthermore, the device housing is composed of a top cover, a cylindrical outer shell, and a housing base that are detachably connected from top to bottom; an installation platform is provided in the middle of the upper end of the housing base; a limit switch mounting platform, a tubular container support ring, a tubular container lower limit platform, and a solenoid valve fixing platform are arranged sequentially along the vertical direction on the inner wall of the cylindrical outer shell; a plurality of placement holes are arranged along the circumferential direction on the tubular container support ring; an air inlet pipe through hole and an air outlet pipe through hole are provided on the side wall of the cylindrical outer shell corresponding to the outer side of each placement hole, and a cable hole and a temperature sensor insertion hole are provided on the side wall of the cylindrical outer shell.

[0009] Furthermore, the cantilevered rotatable metering unit also includes a motor base and a stepper motor; the motor base consists of a chassis and a support column vertically welded to the upper middle part of the chassis; the motor base is fixedly installed on the mounting platform at the upper middle part of the housing; the stepper motor is fixedly installed on the upper end of the support column with the output shaft facing upwards; one end of the cantilever is drivenly connected to the output shaft of the stepper motor.

[0010] The second objective of this invention is achieved through the following technical solution: A multi-channel automatic metering method for trace gas volume, based on the aforementioned multi-channel automatic metering device for trace gas volume, includes the following steps: Step 1: In the initial state, add an equal volume of liquid from the top of each tubular container to the set water level to construct a water column that reflects the change in gas volume. Step 2: Set the scanning and detection parameters, including: setting the number of channels for the gas volume to be measured; calculating and setting the rotation angle required for channel switching based on the center position of adjacent tubular containers; setting the dwell time of each water column; and setting the scanning frequency according to the exhaust pattern. The scanning frequency setting should ensure that all water columns can be scanned within one scanning cycle. Step 3: When the timer of the control unit detects that the scan time has been reached, the following scan procedure is started: Step 4: Start the stepper motor and rotate in the reverse direction. When the starting limit switch is triggered, stop the rotation, record and store the time. At this time, the liquid level sensor is directly above the first water column. Start the air circuit control of the first water column, measure the initial water level, the number of times the reversing solenoid valve is activated and the termination water level of the water column, and store them in the memory. Calculate the cumulative number of times the reversing solenoid valve is activated and display it on the electronic screen. Step 5: When the dwell time in the first water column reaches the set dwell time, the stepper motor rotates forward by a set angle, so that the sensor rotates to be directly above the adjacent water column; start the air circuit control, measure the initial water level of the second water column, the number of times the reversing solenoid valve operates and the termination water level, store them in the memory, calculate and display the cumulative number of times the reversing solenoid valve operates; repeat this step until the exhaust metering of the penultimate water column is completed. Step 6: After the stepper motor rotates to the last water column, the air circuit control process of the last water column is completed. The initial water level, the number of solenoid valve actions and the termination water level of the last water column are measured and stored in the memory. The cumulative number of solenoid valve actions is calculated and displayed. Step 7: When the dwell time of the last water column reaches the set dwell time and the stepper motor rotates forward less than the set angle, the end limit switch is triggered and the scanning stops; Step 8: When the timer reaches the next scan time, repeat steps 3-7.

[0011] The advantages and positive effects of this invention are as follows: 1. This invention achieves continuous and efficient metering of micro-volume gas through multiple channels, solving the technical problem of automatic metering of micro-volume gas in exhaust devices through multiple channels in engineering and scientific research, reducing manual labor and lowering labor costs.

[0012] 2. This invention designs a gas-collecting water column assembly and develops a method combining a gas-collecting bag and a water column. Utilizing a drainage metering unit, it achieves precise measurement of minute amounts of exhaust gas. Simultaneously, it avoids the intersection of the gas and water paths, preventing impurities carried by the exhaust gas from contaminating the water column and causing liquid level measurement errors, as well as preventing the liquid from absorbing some gas components and affecting the accurate analysis of the exhaust gas sample composition in the gas path.

[0013] 3. The control unit of this invention uses a microcontroller as its core and utilizes a stepper motor, two limit switches, and an arc arrangement to achieve sequential switching control of the non-contact liquid level sensor between multiple channels; it uses a reversing solenoid valve, a non-contact liquid level sensor, and a temperature sensor to collect exhaust volume data, so that the continuous exhaust process can be accurately described by discrete data such as the number of actions and water level height; combined with display, parameter input, and data storage functions, it achieves visual and retrieval of data and a high degree of automation.

[0014] 4. The device of the present invention adopts a detachable structure design, which has flexible expansion capabilities and is convenient and efficient in installation, operation and use.

[0015] 5. The device of this invention is equipped with fault detection and alarm functions such as abnormal water level and motor jamming to ensure stable operation of the device. At the same time, combined with temperature compensation design, it further improves the accuracy of gas volume measurement. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the multi-channel micro-volume automatic metering device of the present invention (top cover is in the open state). Figure 2 This is a schematic diagram of the structure of the cantilevered rotatable metering unit of the present invention; Figure 3 This is a schematic diagram of the cylindrical outer shell of the present invention; Figure 4 This is a schematic diagram of the air-collecting water column unit of the present invention; Figure 5 This is a schematic diagram showing the placement of the two limit switches in this invention; Figure 6 This is a control flowchart for gas volume measurement according to the present invention; Figure 7 This is a schematic diagram of the control circuit of the present invention (due to the size limitation of the attached drawing, only 3 metering channels are shown in the control circuit). In the diagram: 1. Top cover; 2. Cylindrical outer shell; 2-1. Limit switch mounting platform; 2-2. Placement hole; 2-3. Lower limit platform of tubular container; 2-4. Solenoid valve mounting platform; 2-5. Cable hole; 2-6. Inlet pipe through hole; 2-7. Outlet pipe through hole; 2-8. Temperature sensor socket; 3. Starting limit switch; 4. Ending limit switch; 5. Cantilever; 6. Tubular container; 7. Reversing solenoid valve; 8. Temperature sensor; 9. Housing base; 10. Bushing assembly; 11. Non-contact liquid level sensor; 12. Stepper motor; 13. Motor base; 14. Pipe cover; 14-1. Sensor probe detection through hole; 15. Gas collection bag; 16. Inlet pipe; 17. Outlet pipe; 18. Sealing plug; 19. Inlet pipe; 20. Outlet pipe. Detailed Implementation

[0017] The structure of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that these embodiments are descriptive and not limiting.

[0018] Please refer to a multi-channel micro-gas volume automatic metering device. Figures 1-7 The invention features multiple sets of gas-collecting water column units, a cantilevered rotatable metering unit, a device housing, a starting limit switch 3, an ending limit switch 4, a temperature sensor 8, a reversing solenoid valve 7, and a control unit.

[0019] Each gas-collecting water column unit adopts a columnar unit that can store water at the top and collect gas at the bottom, mainly including a tubular container 6, a gas-collecting bag 15, and a sealing plug 18. The tubular container is open at both the top and bottom, and a tube cap 14 is further provided at the top of the tubular container to prevent excessive water loss. A sensor probe detection through hole 14-1 is left in the middle of the tube cap; the bottom of the tubular container is sealed with a sealing plug and a gas-collecting bag.

[0020] Sealing method at the bottom of the tubular container: The gas collecting bag is placed inside the tubular container with its opening facing downwards. A sealing plug is inserted into the lower opening of the gas collecting bag and sealed and fixed to the inner wall of the lower end of the tubular container. A sealed gas collecting space is formed inside the gas collecting bag, and a water column receiving cavity is formed inside the tubular container above the gas collecting bag. Two short connecting pipes are fixed through the sealing plug, namely the inlet pipe 16 and the outlet pipe 17. The inlet pipe is connected to the inlet pipe 19 through a reversing solenoid valve, so as to allow the gas discharged from the fermenter to enter the gas collecting bag. The outlet pipe is connected to the outlet pipe 20 through another reversing solenoid valve, so as to allow the gas from the gas collecting bag to be discharged into the surrounding atmosphere.

[0021] The gas collection bag has excellent properties such as resistance to acid and alkali corrosion, certain elasticity, low tension, no tearing or swelling underwater, and low gas permeability. The maximum expansion of the bag body is less than the inner diameter of the tubular container.

[0022] The cantilevered rotatable metering unit mainly includes a motor base 13, a stepper motor 12, a cantilever 5, and a non-contact liquid level sensor 11. The motor base consists of a chassis and a support column vertically welded to the upper center of the chassis. The stepper motor is fixedly mounted on the upper end of the support column with its output shaft facing upwards. One end of the cantilever is driven and connected to the output shaft of the stepper motor. In this invention, one end of the cantilever is connected to another end of the cantilever via a bushing assembly 10. The cantilever is horizontally positioned. The non-contact liquid level sensor is vertically fixed to the other end of the cantilever with its measuring head facing downwards.

[0023] The device housing consists of a top cover 1, a cylindrical outer shell 2, and a base 9, which are detachably connected from top to bottom. These components support, fix, and protect internal structural parts such as multiple gas-water column units, cantilevered rotatable metering units, start-point limit switches, and end-point limit switches. A cover plate is located at the top of the column to prevent dust and environmental interference.

[0024] An installation platform is provided at the upper center of the housing to support and fix the motor base. On the inner wall of the cylindrical housing, a limit switch mounting platform 2-1, a tubular container support ring, a tubular container lower limit platform 2-3, and a solenoid valve fixing platform 2-4 are sequentially arranged along the vertical direction. Multiple placement holes 2-2 are arranged circumferentially on the tubular container support ring. On the side wall of the cylindrical housing, corresponding to the outer side of each placement hole, there is an air inlet pipe through hole 2-6 and an air outlet pipe through hole 2-7. A cable hole 2-5 and a temperature sensor insertion hole 2-8 are also provided on the side wall of the cylindrical housing.

[0025] The number of gas collecting water column units is determined by the number of exhaust channels to be tested, with one group of gas collecting water column units corresponding to one group of exhaust channels to be tested. The tubular containers of multiple groups of gas collecting water column units are respectively inserted into multiple placement holes on the tubular container support ring frame, with the tubular containers arranged in an arc or a complete circle. The sealing plug at the lower end of the tubular container contacts the lower limit platform of the tubular container, achieving the lower limit of the tubular container, ensuring the tubular container is vertical and preventing tipping.

[0026] The cantilevered rotatable metering unit is housed within a cylindrical outer casing. The motor base is fixedly mounted on a mounting platform at the upper center of the casing. The rotation center of the cantilever coincides with the center of the multiple placement holes arranged circumferentially. The distance between the non-contact liquid level sensor and the rotation center of the cantilever is the same as the distance between the center of the placement hole and the center of the multiple placement holes, ensuring that the non-contact liquid level sensor can rotate with the cantilever to a position aligned with the center of the tubular container. Furthermore, the non-contact liquid level sensor is positioned above the gas-collecting water column unit.

[0027] Choose one of the multiple sets of gas-collecting water column units as the first gas-collecting water column unit, and define the positions of the other sets of gas-collecting water column units sequentially along the circumferential arrangement direction of the multiple sets of gas-collecting water column units, which can be clockwise or counterclockwise.

[0028] The starting limit switch and the ending limit switch are installed on a limit switch mounting platform inside the outer shell of the cylinder. The starting limit switch is positioned radially opposite the outer side of the first group of gas-collecting water column units, meaning the starting limit switch, the midpoint of the first group of gas-collecting water column units, and the circumferential center of the multiple placement holes are aligned on a straight line. The ending limit switch is positioned offset from the outer side of the last group of gas-collecting water column units, and the offset angle of the ending limit switch relative to the last group of gas-collecting water column units needs to be smaller than the angle between the adjacent gas-collecting water column units and the center. Figure 5 .

[0029] The temperature sensor is fixedly inserted into the temperature sensor socket on the cylindrical outer shell and is used to measure the ambient temperature and for temperature compensation in gas volume calculation.

[0030] The control unit uses a microcontroller and is equipped with a display screen, buttons, switches, etc., and is housed in an electrical box outside the device casing. The control unit controls the opening and closing of the multi-channel air passages corresponding to multiple sets of gas-collecting water column units, as well as the switching of air intake and exhaust for each air passage. It also controls the cantilevered rotatable metering unit to scan and detect the water column level and level changes of the multiple gas-collecting water column units in an intermittent rotational motion, and stores the detected data and scanning frequency data.

[0031] This multi-channel micro-gas automatic metering device initially adds an equal volume of liquid to the top of each tubular container until a set water level is reached, constructing a water column reflecting changes in gas volume. The water level is designed to ensure that changes in water level remain within the measurable range of the non-contact liquid level sensor, even when the gas collection bag is at its maximum expansion and completely emptied.

[0032] Single-channel gas path switching control: A single exhaust device's gas metering corresponds to a combination of one gas path unit and a set of gas collecting water column units. Multi-channel gas metering requires multiple gas paths connected to the corresponding gas collecting water column units. The gas path unit includes the corresponding water column's inlet pipe, outlet pipe, reversing solenoid valve control, timer, and counter. Temperature compensation is implemented to improve detection accuracy.

[0033] Intake pipe: One end is connected to the exhaust device, and the other end is connected to the intake pipe of the corresponding air collection water column unit through a reversing solenoid valve.

[0034] Air outlet pipeline: One end is connected to the air outlet pipe of the corresponding air collection water column unit through another reversing solenoid valve, and the other end is connected to the atmosphere.

[0035] Parameter settings: Select the parameter values ​​for setting the highest water level and setting the lowest water level when the gas collection bag is not over-inflated and not completely emptied, input them into the control unit, and ensure that the liquid level sensor can detect the water level.

[0036] Air circuit reversing control: Two reversing solenoid valves switch the air circuit state according to the water level control signal, realizing the switching between air intake and exhaust. Initially, both the intake and exhaust pipes are closed. First, the reversing solenoid valve on the intake pipe opens, connecting the intake pipe and allowing the exhaust gas to enter the corresponding gas collection bag, causing the bag to expand and the water column level to rise. When the non-contact level sensor detects that the water level is higher than the set maximum level, it triggers the solenoid valve, causing the air circuit state to switch: the intake pipe closes and the exhaust pipe opens, and the counter increments the number of solenoid valve actions. At this time, the gas in the gas collection bag is discharged into the atmosphere under water pressure, and the water column level drops rapidly. When the level sensor detects that the water level has dropped below the set minimum level, it triggers the solenoid valve, and the air circuit state switches back to the initial state. By using the number of reversing solenoid valve actions, the difference between the highest and lowest water levels, and the initial and final water levels, the exhaust volume and exhaust rate of the corresponding exhaust device over a period of time can be accurately calculated.

[0037] Switching control for multi-channel metering: The multi-channel metering switching control ensures that the non-contact level sensor accurately moves above different water columns to scan water level data. By setting the scanning frequency and residence time per water column, changes in water level in each column are captured promptly, thereby controlling the two reversing solenoid valves to switch in a timely manner for accurate metering of the exhaust volume. The switching control of the metering channels is specifically achieved by controlling the rotation position of the cantilever and the residence time at each water column.

[0038] The switching control scheme is as follows: 1. Input setting parameters: Set the number of channels for the gas volume to be measured; calculate and set the rotation angle required for channel switching based on the center position of adjacent tubular containers. o Set the dwell time (seconds or minutes) for each water column; set the scanning frequency (times / hour) according to the exhaust pattern, ensuring that the parameter values ​​are set so that all water columns can be scanned within one scanning cycle.

[0039] 2. When the timer detects that the scan time has been reached, start the following scan procedure: 3. Start the stepper motor and rotate it in reverse (to prevent the sensor circuit from continuously winding). When the starting limit switch is triggered, stop rotating, record and store the time. At this time, the liquid level sensor is directly above the first water column. Start the air circuit control of the first water column, measure the initial water level, the number of times the reversing solenoid valve actuates, and the final water level, and store them in the memory. Calculate and display the cumulative number of reversing solenoid valve actuations on the electronic screen.

[0040] 4. When the dwell time of the first water column reaches the set dwell time, the stepper motor rotates forward by a set angle, causing the sensor to rotate directly above the adjacent water column. The air circuit control is activated, measuring the initial water level of the second water column, the number of times the reversing solenoid valve actuates, and the final water level, storing these data in the memory. The cumulative number of actuations of the reversing solenoid valve is calculated and displayed. This step is repeated until the exhaust measurement of the penultimate water column is completed, where the set angle is the angle between the adjacent water columns and the center.

[0041] 5. After the stepper motor rotates to the last water column, the air circuit control process of the last water column is completed. The initial water level, the number of solenoid valve actions and the termination water level of the last water column are measured and stored in the memory. The cumulative number of solenoid valve actions is calculated and displayed. 6. When the dwell time of the last water column reaches the set dwell time, and the stepper motor rotates forward less than the set angle, the end limit switch is triggered, and the scanning stops; 7. When the timer reaches the next scan time, repeat steps 3-6.

[0042] Based on the above-mentioned gas path opening and closing control and channel metering switching control, the metering principle and data processing of exhaust volume are as follows: The results of exhaust volume and exhaust rate under standard conditions need to be read from the stored data and analyzed based on the data collected by the system.

[0043] (1) Unit exhaust volume The volume of gas discharged by a single water column in a single exhaust process (i.e., the water level drops from the set maximum to the set minimum), converted to its volume under standard conditions, is denoted as the unit exhaust volume. V 0, the calculation formula is: Among them: Among them: V 0 —Unit displacement under standard conditions, mL; h 高 —Set the maximum water level value, in cm; h 低 —Set the minimum water level value, in cm; s —Cross-sectional area of ​​the water column, cm 2 ; T1 —Actual temperature measured by the temperature sensor, in K; T 2 —Standard temperature (273.15K).

[0044] (2) Exhaust volume of the scanning interval During the interval between two scans, the exhaust volume of a single exhaust device includes the product of the number of exhausts recorded by the counter corresponding to the water column during that interval and the unit exhaust volume, as well as the volume corresponding to the difference between the initial and final water levels during that interval, calculated using the following formula: V = n × V 0 +（h 末 -h 初 ） × s in: V —The volume of gas discharged during the scanning interval, in mL; n —The number of times the air is released by the counter corresponding to a certain water column during this period; V 0 — Unit exhaust volume under standard conditions, mL; h 初 The initial water level for the measurement period is shown in cm. h 终 The final water level was measured in centimeters.

[0045] The total exhaust volume is the sum of the exhaust volumes for all scan intervals.

[0046] (3) Exhaust rate Exhaust rate reflects the amount of exhaust gas per unit time. It is calculated using the set scanning interval and the exhaust gas volume during the interval period, using the following formula: in: Q The average exhaust rate at a certain moment, in ml / min; V The exhaust volume during the scanning period at that moment, in mL; t The set scan time interval is min.

[0047] In addition, the control unit also has a fault detection function, specifically: 1. Water Level Anomaly Alarm: Sets a maximum and a minimum water level limit; the maximum water level is the level when the air collection bag is overfilled; the minimum water level is the level when the air collection bag is completely emptied; if the water level exceeds the limit threshold, a buzzer alarm will sound and the display will show "Water Level Anomaly". 2. Motor jamming detection: If no feedback signal is received from the starting limit switch within a specified time after the stepper motor sends its first drive pulse, the motor is judged to have lost steps or jammed. The motor is also judged to have lost steps or jammed if the number of forward rotations of the stepper electrode is greater than the number of measurement points minus one. In this case, an alarm is triggered promptly, and the display shows "Motor abnormality".

[0048] Example: To measure the exhaust volume and exhaust rate of the three sets of biogas digesters, three metering channels were designed.

[0049] (1) Structure The air-collecting water column unit consists of four groups arranged in an arc shape. Each tubular container is open at both the top and bottom, with a top cover to prevent excessive water loss. A hole in the center of the cover allows the sensor to detect the water level. The bottom of the tubular container is sealed using an air-collecting bag. The air-collecting bag is made of high-density polyethylene film, and its maximum expansion is less than the inner diameter of the tubular container. The bag is placed inside the tubular container with its opening facing downwards, and is sealed and fixed to the bottom of the water column by a sealing plug installed from bottom to top. The sealing plug has two short connecting pipes, serving as the air inlet and outlet.

[0050] The biogas produced by the three fermenters is connected in sequence to the air inlet pipes of the three gas collection water column units through three air inlet pipes. The air inlet and outlet of each gas collection bag are controlled by two reversing solenoid valves.

[0051] Equipment model selected: 1. The microcontroller model is AT89C52. 2. The display screen model is OLED1286412C 3. The stepper motor model is MOTOR-BLDCM, which is connected to the microcontroller via a power interface driver chip that amplifies the drive current of the microcontroller. 4. The power interface driver chip is ULN2003A. 5. The reversing solenoid valve is model G2R-14-DC5, which is connected to the microcontroller via a power interface driver chip that amplifies the microcontroller's drive current. 6. The temperature sensor model is DS18B20. 7. The non-contact liquid level sensor uses an ultrasonic sensor, model SRF04. 8. The timer model is DS1302. 9. The audible alarm model is BUZZER. 10. The serial memory model is AT24C1024. 11. Data transmission model is COMPIM (2) Control process The control system uses the AT89C52 microcontroller as the main control chip and includes functions such as gas path control, channel metering switching control, temperature compensation, timing, counting, display, and storage. After the system starts, based on the water column structure, empirical gas production patterns, and sensor measurement range, parameters such as stepper motor rotation angle, scanning frequency, residence time, measurement point, highest water level, lowest water level, extreme highest water level, and extreme lowest water level are set.

[0052] 1. In the initial state, the air inlet and outlet pipes of all air collection water column units are closed.

[0053] 2. Start scanning: The stepper motor rotates in reverse. When the starting limit switch is triggered, the stepper motor reaches directly above the first water column.

[0054] 3. At this point, the stepper motor stops rotating, the timer records the time, and the first channel for biogas metering is activated: the liquid level sensor measures the current liquid level. h 初 The biogas is stored in the memory; the reversing solenoid valve connected to the air intake pipe activates, opening the air intake pipe; if the biogas production is high, the gas collection bag expands, and the water level rises; when the ultrasonic displacement sensor detects that the water level is higher than the set maximum water level, both reversing solenoid valves of that water column activate, the air intake pipe closes, the exhaust pipe opens, and the count increments by 1; at this time, the biogas is rapidly discharged from the gas collection bag into the atmosphere, and the water level drops rapidly; when the ultrasonic displacement sensor detects that the water level is lower than the set minimum water level, the two reversing solenoid valves activate again, switching to the state of open air intake pipe and closed exhaust pipe; if the biogas production of this group of fermenters is high and cannot be discharged all at once, the above reversing solenoid valve activation process is repeated several times; when there is no excess biogas discharged, the ultrasonic displacement sensor detects the current liquid level. h 末 And store it in the memory; the reversing solenoid valve connected to the intake pipe is activated to close the intake pipe.

[0055] 4. When the timer detects that the residence time of the first water column has reached the set time, channel switching is initiated. The stepper motor rotates forward by the set angle until it reaches directly above the second water column, and the timer records the time. The biogas metering of the second channel is then activated, and the gas path reversal metering control process is the same as in step 3.

[0056] 5. Repeat process 4, with the stepper motor continuing to rotate in the forward direction to complete the venting of all water columns and water level detection, until the end limit switch is triggered, the scanning process stops, and the first scan is completed.

[0057] 6. The temperature sensor stores the temperature data measured by the temperature sensor.

[0058] 7. When the timer detects that the second scan time has arrived (derived from the set scan frequency), the second scan is started. Repeat process 2-6, and so on, to complete the second scan, the third scan, ... the Nth scan.

[0059] During the scanning process, if the water level is detected to be above the maximum limit or below the minimum limit, the buzzer will sound an alarm and the display will show "Abnormal water level".

[0060] During the scanning process: If no feedback signal from the limit switch is received within 10 minutes after the stepper motor sends its first drive pulse, the motor is judged to have lost steps or jammed; if the number of forward rotations of the stepper electrode is greater than 2 (number of measurement points minus 1), the motor is also judged to have lost steps or jammed. At this time, an alarm is triggered in time, and the display shows "Motor abnormality".

[0061] (3) Data processing Export experimental reports to Excel format via USB interface for subsequent data analysis. Press the reset button to clear the current data and start a new experiment.

[0062] The calculation process is explained in the above section on the principle of exhaust volume measurement and data processing.

[0063] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A multi-channel micro-volume automatic metering device, characterized in that: It includes multiple sets of gas-collecting water column units, cantilevered rotatable metering units, device housing, starting limit switch, ending limit switch, temperature sensor, reversing solenoid valve and control unit; Each gas collecting water column unit adopts a columnar unit that can store water column at the top and collect gas at the bottom; multiple gas collecting water column units are placed in multiple placement holes evenly distributed around the center of the device housing; the lower part of each gas collecting water column unit is equipped with a reversing solenoid valve to realize the exhaust input of a channel exhaust device, and each is equipped with another reversing solenoid valve to realize the exhaust of gas in the gas collecting water column unit. The cantilevered rotatable metering unit is installed on the device housing, and the rotation center of the cantilever coincides with the center of the housing. A non-contact liquid level sensor is installed at the end of the cantilever that is away from its rotation center. The non-contact liquid level sensor is located above the gas collecting water column unit. The starting limit switch and the ending limit switch are installed inside the device housing, along the circumferential arrangement direction of multiple sets of gas collecting water column units. The starting limit switch is set on the outer side of the first set of gas collecting water column units in a radially facing position, and the ending limit switch is set on the outer side of the last set of gas collecting water column units at a offset position. The temperature sensor is mounted on the device housing and is used to measure the ambient temperature and for temperature compensation in gas volume calculation. The control unit uses a microcontroller to control the opening and closing of the multi-channel air passages corresponding to multiple sets of gas collecting water column units and the switching control of air intake and exhaust for each air passage. It also controls the cantilevered rotatable metering unit to scan and detect the water column level and water level changes of the multiple gas collecting water column units in an intermittent rotational motion, and stores the detected data and scanning frequency data.

2. The multi-channel micro-volume automatic metering device according to claim 1, characterized in that: The gas collecting water column unit includes a tubular container, a gas collecting bag, and a sealing plug. The tubular container is open at both the top and bottom. The body of the gas collecting bag is placed inside the tubular container with its opening facing downwards. The sealing plug is inserted into the lower opening of the gas collecting bag and is sealed and fixed to the inner wall of the lower end of the tubular container. A sealed gas collecting space is formed inside the gas collecting bag, and a water column receiving cavity is formed above the gas collecting bag inside the tubular container. Two short connecting pipes are fixed through the sealing plug, namely an inlet pipe and an outlet pipe. The inlet pipe is connected to the inlet pipeline through a reversing solenoid valve to allow the gas discharged from the fermenter to enter the gas collecting bag. The outlet pipe is connected to the outlet pipeline through another reversing solenoid valve to allow the gas from the gas collecting bag to be discharged into the surrounding atmosphere.

3. The multi-channel micro-volume automatic metering device according to claim 2, characterized in that: The tubular container is equipped with a cap at the top, and a sensor probe detection hole is left in the middle of the cap.

4. The multi-channel micro-volume automatic metering device according to claim 1, characterized in that: The device housing consists of a top cover, a cylindrical outer shell, and a base that are detachably connected vertically. An installation platform is provided at the middle of the upper end of the base. A limit switch mounting platform, a tubular container support ring, a tubular container lower limit platform, and a solenoid valve fixing platform are arranged sequentially along the vertical direction on the inner wall of the cylindrical outer shell. Multiple placement holes are arranged along the circumferential direction on the tubular container support ring. An air inlet pipe through hole and an air outlet pipe through hole are provided on the side wall of the cylindrical outer shell corresponding to the outer side of each placement hole. A cable hole and a temperature sensor insertion hole are also provided on the side wall of the cylindrical outer shell.

5. The multi-channel micro-volume automatic metering device according to claim 4, characterized in that: The cantilevered rotatable metering unit includes a motor base and a stepper motor; the motor base consists of a chassis and a support column vertically welded to the upper middle part of the chassis; the motor base is fixedly installed on the mounting platform at the upper middle part of the housing; the stepper motor is fixedly installed on the upper end of the support column with the output shaft facing upwards; one end of the cantilever is drivenly connected to the output shaft of the stepper motor.

6. A multi-channel automatic metering method for trace gas volume, based on the multi-channel automatic metering device for trace gas volume according to any one of claims 1-5, comprising the following steps: Step 1: In the initial state, add an equal volume of liquid from the top of each tubular container to the set water level to construct a water column that reflects the change in gas volume. Step 2: Set the scanning and detection parameters, including: Set the number of channels for the gas volume to be measured; calculate and set the rotation angle required for channel switching based on the center position of adjacent tubular containers; Set the dwell time for each water column; The scanning frequency is set according to the exhaust pattern. The scanning frequency setting should ensure that all water columns can be scanned within one scanning cycle. Step 3: When the timer of the control unit detects that the scan time has been reached, the following scan procedure is started; Step 4: Start the stepper motor and rotate in the reverse direction. When the starting limit switch is triggered, stop the rotation, record and store the time. At this time, the liquid level sensor is directly above the first water column. Start the air circuit control of the first water column, measure the initial water level, the number of times the reversing solenoid valve is activated and the termination water level of the water column, and store them in the memory. Calculate the cumulative number of times the reversing solenoid valve is activated and display it on the electronic screen. Step 5: When the dwell time in the first water column reaches the set dwell time, the stepper motor rotates forward by a set angle, so that the sensor rotates to be directly above the adjacent water column; Initiate air circuit control, measure the initial water level of the second water column, the number of times the reversing solenoid valve actuates, and the final water level, store them in the memory, calculate and display the cumulative number of times the reversing solenoid valve actuates; repeat this step until the exhaust metering of the penultimate water column is completed; Step 6: After the stepper motor rotates to the last water column, the air circuit control process of the last water column is completed. The initial water level, the number of solenoid valve actions and the termination water level of the last water column are measured and stored in the memory. The cumulative number of solenoid valve actions is calculated and displayed. Step 7: When the dwell time of the last water column reaches the set dwell time and the stepper motor rotates forward less than the set angle, the end limit switch is triggered and the scanning stops; Step 8: When the timer reaches the next scan time, repeat steps 3-7.

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