Calibration system of NDIR gas sensor

Abstract

The utility model relates to the technical field of sensor calibration, in particular to a calibration system of an NDIR (Non-Dispersive Infra-Red) gas sensor, which comprises a computer, a serial server, a relay module, a gas source group, a mass flow controller, a high-low temperature box, a gas analyzer and a calibration tool frame group for broadcasting calibration. The to-be-calibrated NDIR gas sensor is detachably mounted on the corresponding calibration tool plate and is in communication connection with the calibration tool plate; a storage medium is arranged in the NDIR gas sensor and is used for storing calibration data; the computer is in communication connection with the relay module, the gas analyzer, the mass flow controller, the high and low temperature box and the calibration tool plates through the serial port server. According to the utility model, simultaneous calibration of a plurality of NDIR gas sensors can be conveniently realized in mass production, and a lower-carbon green production environment is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of sensor calibration, and more particularly to a calibration system for an NDIR (Non-Dispersive InfraRed) gas sensor. Background Art

[0002] At present, NDIR gas sensors are widely used in indoor and outdoor air quality monitoring, methane gas leak detection, DCV (demand control ventilation) process, HVAC (heating, ventilation, and air conditioning) system monitoring, smart grid power system status monitoring, medical equipment and surgical operation monitoring, agricultural greenhouse monitoring, transportation cabin and cargo monitoring and other fields because of their advantages such as being not easily affected by harmful gases and being poisoned and aged, fast response and recovery time, good stability, high accuracy and long life.

[0003] However, traditional calibration systems suffer from heavy computational loads, long runtimes, high energy consumption, and high costs. Frequent computer data acquisition and extensive data processing are the root causes of these heavy computational loads, long runtimes, high energy consumption, and high costs. First, the computer must read a large amount of calibration data from each NDIR gas sensor, including the calibration concentration level, calibration temperature level, and corresponding voltage signals (hereinafter referred to as concentration voltage and temperature voltage). The computer then calculates the calibration concentration coefficient and calibration temperature compensation coefficient. Finally, these data are sent to each NDIR gas sensor in turn and await a response. This type of calibration system requires a long runtime and is unsuitable for mass production.

[0004] Therefore, developing a more suitable calibration system is an effective way to simplify the NDIR gas sensor calibration process, improve calibration accuracy, and reduce calibration time and cost, thereby realizing the simultaneous calibration of multiple NDIR gas sensors in mass production and achieving a lower-carbon green production environment. Utility Model Content

[0005] In view of this, the present invention provides a calibration system for NDIR gas sensors, which can conveniently implement simultaneous calibration of multiple NDIR gas sensors in mass production, thus achieving a lower-carbon green production environment.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A calibration system for NDIR gas sensors includes a computer, a serial port server, a relay module, a gas source assembly, a mass flow controller, a temperature chamber, a gas analyzer, and a calibration tool rack assembly. The calibration tool rack assembly is installed within the temperature chamber and is equipped with multiple calibration tool plates. The NDIR gas sensors to be calibrated are removably mounted on and connected to corresponding calibration tool plates. Each NDIR gas sensor is internally provided with a storage medium for storing calibration data.

[0008] Each gas source in the gas source assembly is connected to the high- and low-temperature chamber via a gas circuit. Each gas circuit is equipped with a pressure sensor and a solenoid valve. The relay module is connected to the pressure sensor and the solenoid valve, respectively. The mass flow controller is connected to the solenoid valve via the gas circuit to adjust the gas flow rate.

[0009] The gas analyzer is connected to the high and low temperature box and is used to collect the actual concentration of the gas to be measured in the high and low temperature box.

[0010] The computer is connected to the relay module, the mass flow controller, the high and low temperature box, the gas analyzer and the calibration tooling board through the serial port server, thereby realizing control or data exchange.

[0011] Furthermore, at least two calibration fixtures are installed within the high-temperature and low-temperature chamber, forming a calibration fixture set. Each calibration fixture has multiple layers, each layer having at least two connecting plates. Each connecting plate is connected via gold fingers and holds multiple calibration fixtures. Each calibration fixture has multiple installation numbers. Each NDIR gas sensor is sequentially installed on each installation number.

[0012] Furthermore, a plurality of power supplies are installed on the calibration fixture, and each power supply supplies power to a plurality of the NDIR gas sensors.

[0013] Furthermore, the calibration system also includes a 24V switching power supply, which supplies power to the pressure sensor, the solenoid valve, the relay module and the mass flow controller.

[0014] Furthermore, the gas source group includes a gas cylinder for the gas to be tested, a compressed air source and a nitrogen cylinder.

[0015] Furthermore, each NDIR gas sensor includes an optical sensing unit, an infrared light source, a detector, a bandpass amplifier, a follower, an ADC (Analog-to-Digital Converter) module, an MCU (MicroController Unit) and a driving unit.

[0016] The optical sensing unit has an air inlet and an air outlet. The infrared light source and the detector are disposed relative to each other within the optical sensing unit. The driving unit, under the control of the MCU, drives the infrared light source to emit infrared light. The infrared light emitted by the infrared light source is reflected by the optical sensing unit and enters the detector.

[0017] The detector is equipped with a thermopile device and an NTC (Negative Temperature Coefficient) thermistor, and two pins are led out, namely the thermopile pin PIN1 and the NTC thermistor pin PIN2. The thermopile pin PIN1 is connected to the ADC module through the bandpass amplifier, and the NTC thermistor pin PIN2 is connected to the ADC module through the follower. The MCU is electrically connected to the ADC module to control the sampling of the ADC module. The ADC module collects the peak-to-peak value of the voltage signal output by the bandpass amplifier, which is called the concentration voltage V PP , V PP The change of represents the change of gas concentration. In addition, the ADC module collects the voltage signal output by the follower, which is called the temperature voltage V NTC , where V NTC The fluctuations correspond to changes in temperature.

[0018] The MCU is connected to the calibration tooling board and the serial port server in sequence through a digital communication interface, and receives data capture instructions, data storage instructions and the actual concentration of the gas to be measured in the high and low temperature box broadcast by the computer.

[0019] The storage medium is located inside the MCU, and under the control of the MCU, the concentration voltage V PP , Temperature Voltage V NTC The actual concentration of the gas to be measured is stored.

[0020] 1. The calibration fixture set of the utility model can realize the simultaneous calibration of a large number of NDIR gas sensors. The computer broadcasts data instructions to each NDIR gas sensor through the serial port server, which can reduce the number of data exchanges and data processing tasks between the computer and the NDIR gas sensor.

[0021] The temperature chamber provides a stable calibration temperature level during the NDIR gas sensor calibration process. A gas analyzer detects the actual concentration of the gas to be measured in the temperature chamber, providing a reference for concentration calibration of the NDIR gas sensor. By installing a pressure sensor on each gas source pipeline in the gas source group, the gas source pressure can be monitored in real time to ensure that it meets the requirements and that the gas source in the corresponding gas cylinder is smoothly transmitted to the temperature chamber. Furthermore, by installing a compressed air source and a nitrogen cylinder, nitrogen or air can be introduced into the temperature chamber to adjust the concentration of the gas to be measured, which helps to improve the calibration accuracy of the NDIR gas sensor.

[0022] 2. The computer sends the data capture and data save instructions in sequence by broadcasting. This method is time-saving and has a low computational load. After receiving the instructions, the NDIR gas sensor captures the calibration data and saves it in the internal storage medium, thereby reducing the number of data interactions and data processing tasks of the computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0024] Figure 1 It is a structural diagram of the calibration system of the NDIR gas sensor provided by the utility model.

[0025] Figure 2 It is a structural schematic diagram of the NDIR gas sensor provided by the utility model. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] like Figure 1As shown, an embodiment of the present invention discloses a calibration system for an NDIR gas sensor, comprising: a computer, a serial port server, a relay module, a gas source group, a mass flow controller, a high and low temperature chamber, a gas analyzer, and a calibration fixture rack group. Calibration software is installed in the computer to control and execute broadcast calibration. The calibration fixture rack group is installed in the high and low temperature chamber, and a plurality of calibration fixture boards are installed on the calibration fixture rack group. The NDIR gas sensor to be calibrated is detachably mounted on the calibration fixture board and connected to the corresponding calibration fixture board. A storage medium is set inside each NDIR gas sensor, and the storage medium is used to store calibration data.

[0028] At least two calibration fixtures are installed within the high and low temperature chamber, forming a calibration fixture set. Each calibration fixture has multiple layers, each equipped with at least two connecting plates. Each connecting plate is connected by gold fingers and holds multiple calibration fixtures. Each calibration fixture has multiple mounting numbers. Each NDIR gas sensor is sequentially mounted on each mounting number.

[0029] In this embodiment, each calibration fixture rack has nine layers, each equipped with two serially connected connection boards. Each connection board is connected via gold finger connectors and can hold five calibration fixture boards. Data communication between the NDIR gas sensor and the computer is ultimately achieved through a data link established by the calibration fixture boards, connection boards, serial port server, and computer. Each calibration fixture rack is equipped with a power supply, which supplies power to each NDIR gas sensor via the connection board.

[0030] The computer is connected to the relay module, mass flow controller, high and low temperature box, gas analyzer and calibration tooling board through the serial port server, thereby realizing control or data exchange.

[0031] The gas source group includes a gas cylinder for the gas to be tested, a compressed air source, and a nitrogen cylinder. Each gas source is connected to the high- and low-temperature chamber via a gas circuit, and each gas circuit is equipped with a pressure sensor and a solenoid valve. The relay module is connected to the pressure sensor and the solenoid valve, respectively. The mass flow controller is equivalent to a switch with adjustable opening size. It is connected to the solenoid valve via a gas circuit and is used to adjust the gas flow rate. The relay module controls the solenoid valve to inject nitrogen or air into the high- and low-temperature chamber, thereby reducing the concentration of the gas to be tested inside the high- and low-temperature chamber. At the same time, the relay module reads the input signal from the pressure sensor and feeds it back to the computer to determine whether the gas source pressure meets the requirements.

[0032] The gas analyzer is connected to the high and low temperature box and is used to collect the actual concentration of the gas to be measured in the high and low temperature box.

[0033] At the same time, the calibration system of the present invention is also provided with a 24V switching power supply, and the 24V switching power supply supplies power to the pressure sensor, the relay module, the solenoid valve and the mass flow controller.

[0034] The following combination Figure 2 The composition of the NDIR gas sensor is further explained.

[0035] Each NDIR gas sensor includes an optical sensing unit, an infrared light source, a detector, a bandpass amplifier, a follower, an ADC module, an MCU, and a driver unit.

[0036] The interior of the optical sensing unit is a smooth curved mirror that reflects infrared light and contains the gas to be measured. An air inlet and an air outlet are located at the left and right outer ends of the optical sensing unit. An infrared light source and detector are positioned relative to each other within the optical sensing unit. In this embodiment, the infrared light source is located on the left side of the optical sensing unit. The MCU uses a weak PWM signal to control the driver unit to output a strong PWM signal, causing the infrared light source to emit infrared light. The infrared light is then reflected by the optical sensing unit and transmitted to the detector. During transmission, infrared light of a specific wavelength is partially absorbed by the gas to be measured.

[0037] The detector is located to the right of the optical sensing unit. A filter mounted on its surface allows only infrared light of a specific wavelength to pass through. The detector houses a thermopile device and an NTC thermistor, with two pins extending from it: thermopile pin PIN1 and NTC thermistor pin PIN2. Thermopile pin PIN1 is connected to the ADC module via a bandpass amplifier, while NTC thermistor pin PIN2 is connected to the ADC module via a follower. An MCU is connected to the ADC module to control its sampling.

[0038] The detector is very sensitive to changes in infrared light of a specific wavelength. It converts this specific wavelength of infrared light into a voltage signal through the thermopile device and outputs it through PIN1. Because the voltage signal output by the thermopile pin is weak and nearly sawtooth-shaped, it must be amplified and filtered. Therefore, the bandpass amplifier is required to amplify the effective signal and filter the noise to output a voltage signal close to a sine wave. Under the control of the MCU, the ADC module collects the maximum and minimum values of the voltage signal output by the bandpass amplifier to determine the peak-to-peak value, which is called the concentration voltage and is recorded as V PP , which is proportional to the intensity of infrared light of a specific wavelength incident on the detector. PP Calculate the concentration of the gas to be measured.

[0039] The detector, optical sensing unit, bandpass amplifier, and other components of the NDIR gas sensor are easily affected by the ambient temperature, which can produce an offset voltage signal. Therefore, an NTC thermistor is required so that the MCU can compensate to offset the impact of the ambient temperature. The NTC thermistor inside the detector can convert the ambient temperature into a voltage signal and output it through PIN2. This voltage signal is called temperature voltage and is recorded as V NTC Under the control of the MCU, the ADC module collects temperature voltage and transmits it to the MCU.

[0040] The MCU establishes connections with the calibration tooling board and the serial port server in sequence through the digital communication interface, and receives data capture instructions, data storage instructions and the actual concentration of the gas to be measured in the high and low temperature chamber broadcast by the computer.

[0041] The storage medium is located inside the MCU. Under the control of the MCU, the concentration voltage V PP , Temperature Voltage V NTC The actual concentration of the gas to be measured in the high and low temperature chamber is stored. When the MCU receives the data capture instruction, it obtains the current concentration voltage V PP , Temperature Voltage V NTC And the actual concentration of the gas to be measured. When the data save instruction is received, the concentration voltage V PP , Temperature Voltage V NTC The actual concentration of the gas to be measured is saved in the storage medium. In this way, during the actual calibration process, the NDIR gas sensor can directly retrieve the calibration data from the internal storage medium without frequent data interaction with the computer, thereby shortening the calibration time and improving the calibration efficiency.

[0042] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0043] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A calibration system for an NDIR gas sensor, characterized in that: include: Computer, serial port server, relay module, gas source group, mass flow controller, high and low temperature chamber, gas analyzer and calibration fixture set; The calibration fixture frame is installed in the high and low temperature box, and a plurality of calibration fixture plates are installed on the calibration fixture frame; the NDIR gas sensor to be calibrated is detachably mounted on the corresponding calibration fixture plate and connected to the corresponding calibration fixture plate; a storage medium is provided inside each NDIR gas sensor for storing calibration data; Each gas source in the gas source group is connected to the high and low temperature box through a gas circuit, and each gas circuit is equipped with a pressure sensor and a solenoid valve; The relay module is connected to the pressure sensor and the solenoid valve respectively, and the mass flow controller is connected to the solenoid valve through the gas path to adjust the gas flow rate; The gas analyzer is connected to the high and low temperature box and is used to collect the actual concentration of the gas to be measured in the high and low temperature box; The computer is connected to the relay module, the mass flow controller, the high and low temperature box, the gas analyzer and the calibration tooling board through the serial port server.

2. The calibration system for NDIR gas sensors according to claim 1, characterized in that: At least two calibration fixtures are provided in the high and low temperature chamber to form the calibration fixture group; each calibration fixture has multiple layers, and each layer is provided with at least two connecting plates; each connecting plate is connected by gold fingers and is loaded with multiple calibration fixture plates; each calibration fixture plate has multiple installation numbers; each NDIR gas sensor is installed on each installation number in turn.

3. The calibration system for NDIR gas sensors according to claim 2, characterized in that: A plurality of power supplies are also installed on the calibration fixture, and each power supply supplies power to a plurality of the NDIR gas sensors.

4. The calibration system for NDIR gas sensors according to claim 1, characterized in that: The calibration system further includes a 24V switching power supply, which supplies power to the pressure sensor, the solenoid valve, the relay module, and the mass flow controller.

5. The calibration system for NDIR gas sensors according to claim 1, characterized in that: The gas source group includes a gas cylinder for the gas to be tested, a compressed air source and a nitrogen cylinder.

6. The calibration system for NDIR gas sensors according to claim 2, characterized in that: Each of the NDIR gas sensors includes an optical sensing unit, an infrared light source, a detector, a bandpass amplifier, a follower, an ADC module, an MCU and a driving unit; The optical sensing unit has an air inlet and an air outlet; the infrared light source and the detector are arranged opposite to each other inside the optical sensing unit; the driving unit drives the infrared light source to emit infrared light under the control of the MCU; the infrared light emitted by the infrared light source is reflected by the optical sensing unit and enters the detector; The detector is provided with a thermopile device and an NTC thermistor, and two pins are led out, namely the thermopile pin PIN1 and the NTC thermistor pin PIN2; the thermopile pin PIN1 is connected to the ADC module through the bandpass amplifier, and the NTC thermistor pin PIN2 is connected to the ADC module through the follower; the MCU is electrically connected to the ADC module to control the ADC module sampling; the ADC module collects the peak-to-peak value of the voltage signal output by the bandpass amplifier, which is called the concentration voltage V PP In addition, the ADC module collects the voltage signal output by the follower, which is called the temperature voltage V NTC ; The MCU is connected to the calibration tooling board and the serial port server in sequence through a digital communication interface, and receives the data capture instruction, data save instruction and the actual concentration of the gas to be measured in the high and low temperature box broadcast by the computer; The storage medium is located inside the MCU, and under the control of the MCU, the concentration voltage V PP , Temperature Voltage V NTC The actual concentration of the gas to be measured is stored.

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