A natural gas metering calibration system and calibration method

Abstract

This invention discloses a natural gas metering and calibration system and calibration method, including a differential pressure transmitter, a pressure transmitter, a temperature transmitter, a resistance temperature detector (RTD), a calibration module, an isolator, a signal acquisition module, and a metering system. The calibration module is used to calibrate the isolator. The differential pressure information, pressure information, and temperature information are transmitted to the signal acquisition module via the calibration module and the isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure information, pressure information, and temperature information, and transmits the converted differential pressure data, pressure data, and temperature data to the metering system.

Description

Technical Field

[0001] This invention relates to the field of natural gas production metering technology, specifically to a natural gas metering calibration system and calibration method. Background Technology

[0002] Natural gas metering is a crucial aspect of the natural gas production industry, involving trade settlement and resource management. Natural gas metering management and calibration systems not only need to collect real-time data on natural gas flow, volume, and total quantity, but also require safety monitoring of all stages of natural gas production, including detecting differential pressure, pressure, natural gas temperature, and other harmful gases within pipelines. This real-time data transmission to the metering system is essential. However, existing technology suffers from a problem: after a period of use, isolators used for standard conversion may become inaccurate due to internal component wear or external environmental factors. Without calibration, this leads to inaccurate data transmitted to the metering system. Summary of the Invention

[0003] The present invention aims to provide a natural gas metering and calibration system that can automatically calibrate isolators.

[0004] A natural gas metering and calibration system includes a differential pressure transmitter, a pressure transmitter, a temperature transmitter, a resistance temperature detector (RTD), a calibration module, an isolator, a signal acquisition module, and a metering system. The differential pressure transmitter is used to collect differential pressure information within the natural gas pipeline, the pressure transmitter is used to collect pressure information within the natural gas pipeline, and the temperature transmitter or RTD is used to collect temperature information of the natural gas within the pipeline. The calibration module is used to calibrate the isolator. The differential pressure information, pressure information, and temperature information are transmitted to the signal acquisition module via the calibration module and the isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure information, pressure information, and temperature information, and transmits the converted differential pressure data, pressure data, and temperature data to the metering system.

[0005] The beneficial effects of this invention are as follows: This invention collects differential pressure information in natural gas pipelines through differential pressure transmitters, pressure information in natural gas pipelines through pressure transmitters, and temperature information in natural gas pipelines through temperature transmitters or thermal resistors, thereby achieving real-time detection of differential pressure, pressure, and temperature. This invention also features a specially designed calibration module. When the isolator experiences inaccurate data standard conversion, the calibration module can automatically calibrate the isolator without dismantling, repairing, or replacing it, thus achieving online calibration of the isolator. This does not affect the continuity of monitoring various data in natural gas production, making it highly efficient and practical.

[0006] A preferred embodiment of the present invention is that: the calibration module is further used to collect the status information of the isolator; the calibration module transmits the status information, received differential pressure information, pressure information, and temperature information to the main control module through a switch; and the main control module controls whether the calibration module automatically starts calibrating the isolator based on the status information of the isolator.

[0007] The beneficial effects are as follows: This invention actively collects the status information of the isolator through the calibration module, and judges the status of the isolator through the main control module. The status of the isolator includes the isolator's own device parameter information and the isolator's output data, thereby determining whether the isolator needs calibration. When calibration is required, the main control module controls the calibration module to switch the line. The calibration module switches the line that needs to be calibrated from the data acquisition mode to the calibration signal generation mode, thereby realizing the online automatic calibration of a certain isolator.

[0008] A preferred embodiment of the present invention is that the calibration module calibrates the thermal resistance value output by the isolator by generating an analog resistance signal, wherein the analog resistance signal is generated by combining PWM with a reference voltage.

[0009] The beneficial effects are as follows: When collecting the temperature signal of natural gas in a natural gas pipeline through a thermal resistor, since the final temperature signal is reflected by the resistance value, it is necessary to generate a standard analog resistance signal when calibrating the isolator of this path. The analog resistance signal of this invention is generated by combining PWM and reference voltage, which can ensure the accuracy of the analog signal in a large range of -100-800℃, and no program parameter compensation is required, which can avoid the problem of inaccurate calibration signal or calibration failure due to program errors.

[0010] In a preferred embodiment of the present invention, the calibration module is further configured to supply power to the isolator.

[0011] The beneficial effects are: this design is equivalent to the calibration module and the isolator sharing a power supply, which simplifies the power line layout and makes the structure simpler.

[0012] A preferred embodiment of the present invention further includes a flow meter field diagnostic module, which is used to detect flow meter information in real time. The flow meter information is transmitted to the switch through the first communication interface, and then transmitted to the main control module via the switch. The flow meter information includes the flow meter's pressure information, temperature information, operating flow rate, standard flow rate, and total flow rate collected by the flow meter. The main control module determines whether the flow meter is faulty based on the received flow meter information. If so, it issues a fault message and controls the corresponding flow meter to stop detection. It also determines whether the flow meter needs calibration based on the flow meter information. If so, it sends calibration information to the flow meter.

[0013] The beneficial effects are as follows: In this invention, the flow meter is used to detect the flow rate, standard flow rate, and total flow rate of natural gas in real time. If the flow meter malfunctions and is not repaired in time, it will affect the entire metering system. Currently, the conventional practice is to manually conduct irregular inspections to check for flow meter malfunctions, which is labor-intensive and inefficient. This invention equips each flow meter with a field diagnostic module, which detects flow meter information in real time. The flow meter information includes the flow meter's pressure and temperature information, the operating flow rate, standard flow rate, and total flow rate collected by the flow meter. The flow meter information is transmitted to the switch through the first communication interface, and then to the main control module. The main control module determines whether the flow meter is malfunctioning based on the received flow meter information. If the temperature, pressure, and other information collected by the field diagnostic module exceed the set values, it indicates that the flow meter is malfunctioning and needs to be repaired in time. Therefore, a fault message can be issued in time and the corresponding flow meter can be controlled to stop detection. If the collected flow information is inaccurate, it is determined that the flow meter needs to be calibrated. Therefore, online diagnosis and calibration of the flow meter can be realized.

[0014] A preferred embodiment of the present invention further includes a field diagnostic module for the detector. This field diagnostic module is used to detect detector information in real time. The detector information includes temperature and humidity information collected by the detector, as well as the detector's power supply voltage and current. The detector information is transmitted to a switch via a second communication interface, and then to the main control module via the switch. The main control module determines whether the detector is faulty based on the detector information. If so, it issues a fault message and controls the corresponding detector to stop detecting. The main control module is also used to determine whether the detector needs calibration based on the received detector information. If so, it sends calibration information to the corresponding detector.

[0015] The beneficial effects are as follows: The detector described in this invention is used to detect the gas composition at natural gas production sites, thereby monitoring the status of harmful gases in real time. Conventionally, fault diagnosis of detectors is carried out through manual inspection, which is not only time-consuming and labor-intensive, but also inefficient and prone to missed detections. This invention, by setting up an on-site diagnostic module for the detectors, can achieve online diagnosis of each detector without shutting down the system. By collecting information such as temperature, humidity, power supply voltage, and power supply current from the detectors, the main control module compares the collected information with standard or set values ​​to determine whether the detectors are faulty. When a detector malfunctions, the system controls the detector to stop detecting. If the detector needs calibration, the system controls the detector to automatically perform calibration to improve the accuracy of the detection data.

[0016] A preferred embodiment of the present invention is that: the detector information is also transmitted to the alarm controller; when a detector malfunction is detected, the alarm controller controls the alarm to be triggered; the alarm controller communicates with the SCADA system.

[0017] The beneficial effects are as follows: To promptly alert on-site personnel when the detector malfunctions, this invention also includes an alarm controller installed on-site. This controller issues alarm notifications. Furthermore, the alarm controller communicates with the SCADA system (i.e., a data acquisition and monitoring control system) to monitor the on-site situation in real time.

[0018] A preferred embodiment of the present invention is that the operating information of the alarm controller is transmitted to the switch through the second communication interface, and then transmitted to the main control module through the switch, so that the main control module can monitor the operating status of the alarm controller.

[0019] The beneficial effects are as follows: In order to realize online monitoring of whether the alarm controller is abnormal, the alarm controller's operating information is transmitted to the switch through the second communication interface, and then transmitted to the main control module through the switch. The main control module monitors the operating status of the alarm controller, so that timely maintenance can be carried out when the alarm controller fails.

[0020] A preferred embodiment of the present invention is that: the main control module and the metering system communicate bidirectionally; the detector information and flow meter information collected by the main control module are transmitted to the metering system for display; the metering system is used to send start / stop operation commands, parameter setting commands, calibration commands for detectors and flow meters, and calibration commands for differential pressure transmitters, pressure transmitters, temperature transmitters, and resistance thermometers to the main control module.

[0021] The beneficial effects are as follows: the main control module and the metering system of this invention communicate bidirectionally, so that the metering system can intuitively view the information of the detector and the information collected by the flow meter. The metering system belongs to the central control system, and various operating instructions can also be directly sent to the main control module through the metering system to realize the overall and efficient control of the natural gas production process.

[0022] A preferred embodiment of the present invention is as follows: the calibration module includes a signal input conversion module, a reference voltage module, an output modulation module, an AD sampling module, and a standard signal modulation module. The signal input conversion module is used to generate a corresponding PWM signal based on a given value. The reference voltage module is used to generate a reference voltage, derive a corresponding output voltage based on the real-time acquired current and the resistance value to be simulated, modulate the reference voltage through the PWM signal, and then control the output voltage through the output modulation module. The AD sampling module samples the current and the output voltage, and the standard signal modulation module modulates the sampled current and the output voltage to generate a standard signal and output it.

[0023] The beneficial effects are as follows: This solution uses PWM frequency modulation and a reference voltage feedback resistor to ensure the accuracy of analog signals over a large range of -100 to 800°C, without the need for program parameter compensation.

[0024] The second objective of this invention is to provide a natural gas metering calibration method, comprising the following:

[0025] The collected differential pressure, pressure, and temperature information are transmitted to the signal acquisition module via the calibration module and isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure, pressure, and temperature information and then transmits the converted differential pressure, pressure, and temperature data to the metering system.

[0026] The calibration module collects the status information of the isolator, and the main control module controls whether the calibration module automatically starts the calibration of the isolator based on the status information of the isolator.

[0027] If so, the isolator will be automatically calibrated via the calibration module.

[0028] A preferred embodiment of the present invention involves: a calibration module generating an analog resistance signal as a standard signal to calibrate the thermal resistance value output by the isolator; the analog resistance signal is generated using a combination of PWM and a reference voltage.

[0029] The natural gas metering and calibration system provided by this invention, capable of automatically calibrating isolators, has the following advantages:

[0030] This invention uses a differential pressure transmitter to collect differential pressure information within the natural gas pipeline, a pressure transmitter to collect pressure information within the pipeline, and a temperature transmitter or resistance temperature detector (RTD) to collect temperature information of the natural gas within the pipeline. This enables real-time monitoring of differential pressure, pressure, and temperature. A unique calibration module is designed to automatically calibrate the isolator when inaccurate data standard conversion occurs, eliminating the need for disassembly, repair, or replacement. This online calibration of the isolator does not affect the continuity of monitoring data in natural gas production, making it highly efficient and practical.

[0031] The present invention provides a natural gas metering calibration method, which includes collecting differential pressure information, pressure information, and temperature information and transmitting them to a signal acquisition module via a calibration module and an isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure information, pressure information, and temperature information, and transmits the converted differential pressure data, pressure data, and temperature data to the metering system. The calibration module collects the status information of the isolator, and the main control module controls whether the calibration module automatically starts calibrating the isolator based on the status information of the isolator. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the natural gas metering and calibration system of the present invention.

[0033] Figure 2 This is a circuit diagram of the analog resistor for generating temperature calibration in the natural gas metering and calibration system of the present invention. Detailed Implementation

[0034] In the following, the terms “comprising” or “may include” as used in various embodiments of the invention indicate the presence of an inventive function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of the invention, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0035] The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of the invention. Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. The terms (such as those defined in commonly used dictionaries) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning unless clearly defined in the various embodiments of the invention.

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0037] As attached Figure 1 The natural gas metering and calibration system shown includes a differential pressure transmitter, a pressure transmitter, a temperature transmitter, a resistance temperature detector (RTD), a calibration module, an isolator, a signal acquisition module, a flow meter field diagnostic module, a detector field diagnostic module, an alarm controller, and a metering system. The calibration module supplies power to the isolator.

[0038] The differential pressure transmitter is used to collect differential pressure information in the natural gas pipeline, the pressure transmitter is used to collect pressure information in the natural gas pipeline, and the temperature transmitter or RTD is used to collect temperature information of the natural gas in the natural gas pipeline. The differential pressure information, pressure information, and temperature information are transmitted to the signal acquisition module via the calibration module and the isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure information, pressure information, and temperature information, and transmits the analog-to-digital converted differential pressure data, pressure data, and temperature data to the metering system.

[0039] The calibration module is used to calibrate the isolator. Specifically, the calibration module is also used to collect the status information of the isolator. The calibration module transmits the status information, received differential pressure information, pressure information, and temperature information to the main control module through a switch. The main control module controls whether the calibration module automatically starts calibrating the isolator based on the status information of the isolator. The status information of the isolator includes the standard conversion value information of the isolator.

[0040] In this embodiment, the calibration module calibrates the output thermistor value by generating an analog resistance signal. This analog resistance signal is generated using a combination of PWM and a reference voltage. The calibration module includes a signal input conversion module, a reference voltage module, an output modulation module, an AD sampling module, and a standard signal modulation module. The signal input conversion module generates a corresponding PWM signal based on a given value. The reference voltage module generates a reference voltage and derives the corresponding output voltage based on the real-time acquired current and the resistance value to be simulated. The reference voltage is modulated using the PWM signal, and the output voltage is then controlled by the output modulation module. The AD sampling module samples the current and output voltage, and the standard signal modulation module modulates the sampled current and output voltage to generate and output a standard signal.

[0041] More specifically, the circuit principle for calibrating the RTD signal in the isolator and generating an analog resistance signal in this embodiment is shown in the attached figure. Figure 2 As shown, it includes a signal input conversion module, an isolation module, a reference voltage module, a first integrated operational amplifier module, an output modulation module, a second integrated operational amplifier module, an AD sampling module, and a standard signal modulation module.

[0042] The signal input conversion module is used to generate a corresponding PWM signal based on a given value (referring to the resistance value input by the user; for example, if a 40Ω analog resistance is desired, then 40 is input). Specifically, this is generated by a central processing module, which is an ST STM32F103ZET6 MCU. The generated PWM signal is input through pin 3 of the isolation module, and output through pin 14 of the isolation module and resistor R101 to pin 6 of the reference voltage module. The reference voltage module is used to generate a reference voltage. In this embodiment, pins 1 and 5 of the reference voltage module are connected to a 2.5V reference voltage, and pins 2 and 3 are grounded. The output from pin 4 of the reference voltage module is output to the first integrated operational amplifier module via a first-stage voltage divider circuit and a multi-stage filter circuit. Specifically, the output from pin 4 of the reference voltage module is first divided by resistors R100 and R103, then filtered and rectified sequentially by resistors R99 and capacitors C94, R98 and C93, R97 and C92, and C91, and finally input to pin 3 of the first integrated operational amplifier module via capacitive matching by capacitor C90. In this embodiment, a two-stage voltage divider circuit and a filter circuit are connected between the first integrated operational amplifier module and the output modulation module. Specifically, the first integrated operational amplifier module... The output from pin 6 of the first operational amplifier module is fed into the output modulation module after being divided by resistors R102 and R104 and filtered by capacitor C95. In this embodiment, the output modulation module uses a first MOSFET, specifically the input is to the gate (G) of the first MOSFET. The drain (D) end of the first MOSFET is connected to the negative feedback terminal of the first integrated operational amplifier module via a filter to ground through resistor R96 and capacitor C89, and capacitors R105 and C98. Capacitors C89 and C98 form a capacitor on the line between the drain of the first MOSFET and the negative feedback terminal of the first integrated operational amplifier module to isolate external signal interference. Resistor C97 is also connected between the line between pin 6 of the first integrated operational amplifier module and resistor R102 and the negative feedback terminal of the first integrated operational amplifier module.

[0043] One end of the drain (D) of the first MOSFET is connected to the ambient temperature input RA (pin 1 of CZ8), and the other end is connected to pin 2 of the negative feedback terminal of the first integrated operational amplifier module via resistor R105. This provides real-time feedback of the analog signal output, thereby changing the output voltage of the operational amplifier to control the first MOSFET. The source (S) terminal is connected to the ambient temperature input RB (pins 2 and 3 of CZ8) via resistors JR1 and JR2. The upper ends of resistors JR1 and JR2 are connected to the amplification circuit and the impedance matching circuit, then to the AD sampling module to acquire the real-time current value. By using the user-defined resistance value and the acquired current value, the voltage of the first MOSFET is controlled, thus obtaining the desired analog resistance value.

[0044] In this embodiment, a second integrated operational amplifier module is connected between the output modulation module and the AD sampling module. Specifically, the source (S) terminal of the first MOSFET is filtered and input to pin 3 of the second integrated operational amplifier module via resistor R106 and capacitor C102. Pin 6 of the second integrated operational amplifier module is connected to one end of resistor R108, which is used to generate real-time current when the output voltage is applied. Pin 6 of the second integrated operational amplifier module is connected to the negative feedback terminal of the second integrated operational amplifier module via a parallel resistor R117 and capacitor C105. A resistor R120 is also connected between the negative feedback terminal of the second integrated operational amplifier module and ground.

[0045] In this embodiment, the other end of resistor R108 is connected to a multi-stage impedance matching circuit in sequence. Specifically, the other end of resistor R108 is connected to one end of resistor R107 and one end of resistor R111, the other end of resistor R107 is connected to a 2.5V power supply, the other end of resistor R111 is grounded, and the other end of resistor R108, after passing through resistor R107 and resistor R111, passes through resistor R109 and capacitor C104 in sequence, and then through resistor R110 and capacitor C103 for filtering and rectification before being input to pin 5 of the AD sampling module. In this embodiment, the AD sampling module uses the AD7792 chip.

[0046] In this embodiment, the standard signal modulation module includes three sets of standard signal modulation sub-modules that are respectively connected to multiple output pins of the AD sampling module. The first set of standard signal modulation submodules includes a parallel resistor R143 and a capacitor C106 connected in series with pin 7 of the AD sampling module, and a parallel resistor R142 and a capacitor C107. The first set of standard signal modulation submodules also includes a third integrated operational amplifier module. Pin 3 of the third integrated operational amplifier module is connected to one end of resistor R149 and resistor R151 respectively. The other end of resistor R149 is connected to a 2.5V power supply, and the other end of resistor R151 is grounded. A capacitor C127 is also connected between the 2.5V power supply and ground. Pin 1 of the third integrated operational amplifier module is connected to the standard signal modulation output circuit. In this embodiment, the standard signal modulation output circuit uses a second MOSFET. Specifically, pin 1 of the third integrated operational amplifier module is connected to the gate (G) of the second MOSFET via resistor R150 and capacitor C126. One end of the source (S) of the second MOSFET is connected to the negative feedback terminal of the third integrated operational amplifier module, and the other end is connected to one end of resistor RJ1. The other end of resistor RJ1 is connected to a 2.5V power supply. Resistor R152 is connected to the drain (D) of the second MOSFET.

[0047] The output terminal of the AD sampling module has a resistor R145 and a capacitor C122 connected in series in parallel, and a resistor R144 and a capacitor C123 connected in parallel in series. The output terminals of the AD sampling module have a resistor R147 and a capacitor C124 connected in series in parallel, a resistor R146 connected in series, and a capacitor C125 and a resistor R148 connected in parallel in series.

[0048] In this embodiment, the analog resistors generated on the line between the impedance matching circuit and the drain of the second MOS transistor, respectively, and on the same lines as those in the other two sets of standard signal modulation submodules, are used as standard signal outputs, as shown in the attached diagram. Figure 1 The analog resistances generated between RA and RB, and between RA and RC, are shown as standard signal outputs.

[0049] In this embodiment, pins 11, 12, and 13 of the isolation module are also connected to pins 15, 16, and 1 of the AD sampling module, which is used to perform control sampling based on the PWM signal.

[0050] This invention derives the corresponding output voltage based on the real-time acquired current and the resistance value to be simulated. The reference voltage is modulated by a PWM signal, and the output voltage is controlled by the output modulation module after modulation. The AD sampling module samples the current and the output voltage, and the standard signal modulation module modulates the sampled current and the output voltage to generate a standard signal and output it.

[0051] An output buffer is employed to allow for a low-impedance analog output while using a high-impedance filter resistor. The output of the first integrated operational amplifier module is connected to resistor R106, and the output of the second integrated operational amplifier module is directly connected to the inverting input of the second integrated operational amplifier. The second integrated operational amplifier module, connected to resistor R108, forms a buffered follower, improving gain accuracy. This buffer is powered by an external high-precision 2.5V reference to obtain a stable full-scale output, thus ensuring the PWM signal swing remains between a low potential and an accurate high level.

[0052] This power supply trimming / margin adjustment application circuit, when connected to a high level, selects "sample / hold" operation. The output is high impedance (no margin adjustment) at startup. A continuous high level on input VDD1 will cause the output to hold its value indefinitely, while a continuous low level AD-DIN2 will place the output in a high-impedance state. Therefore, a PWM burst pulse (followed by a high level) can be used to trim the power supply upon power-up. Pulling the PWM signal low cleanly exits the margin adjustment operation, resulting in a stable power output.

[0053] In this embodiment, the differential pressure signal, pressure signal and temperature signal collected by the temperature transmitter in the isolator are calibrated by current simulation. The method of generating the simulated current is relatively simple and belongs to the prior art, so it will not be described in detail in this embodiment.

[0054] In this embodiment, the flowmeter field diagnostic module is used to detect flowmeter information in real time. This flowmeter information is transmitted to the switch via the first communication interface, and then to the main control module via the switch. The flowmeter information includes the flowmeter's pressure and temperature information, the operating flow rate, standard flow rate, and total flow rate collected by the flowmeter. The main control module determines whether the flowmeter is faulty based on the received flowmeter information. If so, it issues a fault message and controls the corresponding flowmeter to stop detection. It also determines whether the flowmeter needs calibration based on the flowmeter information. If so, it sends calibration information to the flowmeter. In this embodiment, the flowmeter is an orifice plate flowmeter. Abnormal flowmeter faults include abnormal exit, unchanged reading, communication interruption, and power failure.

[0055] The on-site diagnostic module of the detector is used to detect detector information in real time. The detector information includes temperature and humidity information collected by the detector, power supply voltage and current of the detector. The detector information is transmitted to the switch through the second communication interface, and then to the main control module through the switch. The main control module determines whether the detector is faulty based on the detector information. If so, it issues a fault message and controls the corresponding detector to stop detection. The main control module is also used to determine whether the detector needs to be calibrated based on the received detector information. If so, it sends calibration information to the corresponding detector.

[0056] The detector information is also transmitted to the alarm controller. When a detector malfunction is detected, the alarm controller issues an alarm notification. The alarm controller communicates with the SCADA system. The alarm controller's operating information is transmitted to the switch via a second communication interface, and then to the main control module, which monitors the alarm controller's operating status.

[0057] In this embodiment, the main control module and the metering system communicate bidirectionally. The detector and flow meter information collected by the main control module are transmitted to the metering system for display. The metering system sends start / stop commands, parameter setting commands, detector and flow meter calibration commands, and differential pressure transmitter, pressure transmitter, temperature transmitter, and RTD calibration commands to the main control module. In this embodiment, the main control module also counts the number of abnormal alarms and their causes, and transmits this information to the metering system.

[0058] This embodiment also discloses a natural gas metering calibration method, including the following:

[0059] The collected differential pressure, pressure, and temperature information are transmitted to the signal acquisition module via the calibration module and isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure, pressure, and temperature information and then transmits the converted differential pressure, pressure, and temperature data to the metering system.

[0060] The calibration module collects the status information of the isolator, and the main control module controls whether the calibration module automatically starts the calibration of the isolator based on the status information of the isolator.

[0061] If so, the isolator will be automatically calibrated via the calibration module.

[0062] The calibration module generates an analog resistance signal as a standard signal to calibrate the thermal resistance value output by the isolator. The analog resistance signal is generated by combining PWM with a reference voltage.

[0063] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. Typical known structures and common knowledge techniques in the preferred embodiments have not been described in detail here. Those skilled in the art can improve and implement the technical solutions of this invention based on the guidance provided in these embodiments and their own capabilities. Some typical known structures, known methods or common knowledge techniques should not be obstacles for those skilled in the art to implement this application.

[0064] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A natural gas metering and calibration system, characterized in that, The system includes a differential pressure transmitter, a pressure transmitter, a temperature transmitter, a resistance temperature detector (RTD), a calibration module, an isolator, a signal acquisition module, and a metering system. The differential pressure transmitter is used to collect differential pressure information within the natural gas pipeline, the pressure transmitter is used to collect pressure information within the natural gas pipeline, and the temperature transmitter or RTD is used to collect temperature information of the natural gas within the pipeline. The calibration module is used to calibrate the isolator. The differential pressure information, pressure information, and temperature information are transmitted to the signal acquisition module via the calibration module and the isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure information, pressure information, and temperature information, and transmits the converted differential pressure data, pressure data, and temperature data to the metering system. The calibration module is also used to collect the status information of the isolator. The calibration module transmits the status information, received differential pressure information, pressure information, and temperature information to the main control module through a switch. The main control module controls whether the calibration module automatically starts calibrating the isolator based on the status information of the isolator.

2. The system as described in claim 1, characterized in that, The calibration module calibrates the thermal resistance value output by the isolator by generating an analog resistance signal, which is generated by combining PWM with a reference voltage.

3. The system as described in claim 1, characterized in that, The calibration module is also used to power the isolator.

4. The system as described in claim 1, characterized in that, It also includes a flow meter field diagnostic module, which is used to detect flow meter information in real time. The flow meter information is transmitted to the switch through the first communication interface, and then to the main control module via the switch. The flow meter information includes the flow meter's pressure information, temperature information, operating flow rate, standard flow rate, and total flow rate collected by the flow meter. The main control module determines whether the flow meter is faulty based on the received flow meter information. If so, it issues a fault message and controls the corresponding flow meter to stop detection. It also determines whether the flow meter needs to be calibrated based on the flow meter information. If so, it sends calibration information to the flow meter.

5. The system as described in claim 1, characterized in that, It also includes a field diagnostic module for the detector, which is used to detect detector information in real time. The detector information includes temperature and humidity information collected by the detector, as well as the power supply voltage and current of the detector. The detector information is transmitted to the switch through the second communication interface, and then to the main control module via the switch. The main control module determines whether the detector is faulty based on the detector information. If so, it issues a fault message and controls the corresponding detector to stop detecting. The main control module is also used to determine whether the detector needs to be calibrated based on the received detector information. If so, it sends calibration information to the corresponding detector.

6. The system as described in claim 1, characterized in that, The detector information is also transmitted to the alarm controller. When a fault is detected in the detector, the alarm controller will issue an alarm notification. The alarm controller communicates with the SCADA system.

7. The system as described in claim 1, characterized in that, The alarm controller's operating information is transmitted to the switch via the second communication interface, and then transmitted to the main control module via the switch, so that the main control module can monitor the operating status of the alarm controller.

8. The system as described in claim 1, characterized in that, The main control module and the metering system communicate bidirectionally. The detector and flow meter information collected by the main control module are transmitted to the metering system for display. The metering system is used to send start / stop operation commands, parameter setting commands, calibration commands for detectors and flow meters, and calibration commands for differential pressure transmitters, pressure transmitters, temperature transmitters, and RTDs to the main control module.

9. The system as described in claim 1, characterized in that, The calibration module includes a signal input conversion module, a reference voltage module, an output modulation module, an AD sampling module, and a standard signal modulation module. The signal input conversion module generates a corresponding PWM signal based on a given value. The reference voltage module generates a reference voltage and derives the corresponding output voltage based on the real-time acquired current and the resistance value to be simulated. The reference voltage is modulated by the PWM signal, and the output voltage is controlled by the output modulation module. The AD sampling module samples the current and output voltage. The standard signal modulation module modulates the sampled current and output voltage to generate a standard signal and output it.

10. A natural gas metering calibration method, characterized in that, The collected differential pressure, pressure, and temperature information are transmitted to the signal acquisition module via the calibration module and isolator. The signal acquisition module performs analog-to-digital conversion on the differential pressure, pressure, and temperature information and then transmits the converted differential pressure, pressure, and temperature data to the metering system. The calibration module collects the status information of the isolator, and the main control module controls whether the calibration module automatically starts the calibration of the isolator based on the status information of the isolator. If so, the isolator will be automatically calibrated via the calibration module; The calibration module generates an analog resistance signal as a standard signal to calibrate the thermal resistance value output by the isolator. The analog resistance signal is generated by combining PWM with a reference voltage.

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