Device and method for measuring trace oxygen content

Abstract

The invention relates to a trace oxygen content measuring device and method, the device comprises an oxygen pump unit, an oxygen sensing unit, a common electrode unit, a microprocessor and a heating assembly, the current of the oxygen pump unit is in positive correlation with the oxygen content in the environment, and the oxygen sensing unit outputs a voltage signal in proportion to the oxygen content. And the microprocessor adjusts the current of the oxygen pump unit according to the signal of the oxygen sensing unit and maintains the voltage signal at a preset target value to form closed-loop control. The heating assembly keeps the temperature of the sensor constant. The device can realize ppm-level accurate measurement, has high stability and accuracy, reduces the maintenance cost, reduces the reject ratio, improves the production efficiency, reduces the manufacturing cost, and is suitable for various industrial environments. The method is particularly suitable for inert reflow soldering and wave soldering, and the soldering quality and the product reliability are improved.

Description

Technical Field

[0001] The present invention relates to the field of sensor measurement technology, and in particular to a device and method for measuring trace oxygen content. Background Art

[0002] In the field of inert reflow ovens and wave soldering ovens, oxygen content is an important measurement indicator that directly affects welding quality and product reliability. In particular, trace oxygen content (usually refers to very low oxygen content, in ppm) needs to be strictly controlled to prevent oxidation reactions during the welding process, thereby improving the strength and reliability of solder joints, improving production efficiency, ensuring product quality, and reducing production costs.

[0003] During reflow and wave soldering, nitrogen, as an inert gas, can effectively reduce the oxygen content in the air and prevent oxidation reactions during the soldering process. Usually, the oxygen content of flowing nitrogen is required to be less than 1000ppm to ensure the stability and consistency of the soldering process.

[0004] At present, in order to monitor and control the oxygen content, an oxygen content analyzer is required, and the measurement of oxygen content is mainly obtained by sensors collecting sensor data, and the corresponding controller obtains it through specific calculations based on the data collected by the sensors.

[0005] Existing methods for measuring oxygen content include electrochemical method (fuel cell method), limiting current method, and optical trace oxygen sensor method. They all have a problem. When the sensor is affected by external environmental changes (temperature) or works for a long time, the data collected by the sensor has a large deviation, which makes the oxygen content calculated by the microprocessor have a large error. In addition, the sensor is easily damaged and the cost is high.

[0006] Existing trace oxygen measurement methods include electrochemical method (fuel cell method), limiting current method, and optical trace oxygen sensor method.

[0007] Fuel cell method: Low energy density, requires frequent replacement or charging, and cannot monitor oxygen content for a long time. Relatively short life, and can cause sensor aging and damage in harsh environments (large amounts of solder volatilize during reflow soldering). High cost, and large-scale application costs will increase significantly.

[0008] Limiting current method: Most limiting current oxygen sensors are small-pore and porous diffusion types, and their gaps are easily blocked by impurities, resulting in reduced sensor performance or even failure, which requires frequent replacement of sensors and increases costs.

[0009] Optical method: The optical trace oxygen method is a sensor that measures the change in the luminous intensity of fluorescent materials when exposed to oxygen to reflect the oxygen concentration. However, since fluorescent materials require advanced technology and materials, their manufacturing costs are relatively high, which in turn leads to high product prices. It is sensitive to environmental factors such as temperature and humidity. Its performance and accuracy may be affected in the manufacturing environment of reflow soldering or wave soldering, which limits its application to a certain extent.

[0010] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0011] The main purpose of the present invention is to overcome the defects existing in the above-mentioned background technology and provide a device and method for measuring trace oxygen content.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] A device for measuring trace oxygen content, comprising:

[0014] An oxygen pump unit, wherein the current generated by the oxygen pump unit is positively correlated with the oxygen content in the actual environment;

[0015] An oxygen sensing unit, which is used to detect changes in the oxygen content of the sensor's internal environment caused by the oxygen pump unit; wherein, by measuring a potential difference related to the oxygen concentration, a voltage signal is output, and the voltage signal is proportional to the oxygen content in the sensor;

[0016] a common electrode unit that provides a common electrical reference point for the oxygen pump unit and the oxygen sensing unit;

[0017] a microprocessor, which receives the voltage signal of the oxygen sensing unit; compares the received voltage signal with a predetermined target value; and adjusts the current applied to the oxygen pump unit according to the comparison result so that the voltage signal reaches and is maintained at the predetermined target value, thereby forming a closed-loop control system; the predetermined target value is a voltage value corresponding to a specific oxygen content determined by calibration;

[0018] Heating assembly, which is used to maintain the sensor's operating temperature constant.

[0019] Furthermore, the microprocessor achieves precise regulation of the oxygen pump unit current through digital PID control to achieve a predetermined oxygen sensing unit voltage target value.

[0020] Furthermore, the target value is 450mV.

[0021] Furthermore, it also includes:

[0022] A sampling resistor, used to measure the voltage applied to the oxygen pump unit;

[0023] The current detection circuit is used to calculate the voltage drop through the sampling resistor and divide it by the sampling resistor value to obtain a current signal representing the current value of the oxygen pump unit.

[0024] Furthermore, a temperature control unit is included, which is used to maintain a constant operating temperature of the sensor, and includes:

[0025] A negative current pulse generator, used for inputting a negative current pulse (I_RPVS) into the oxygen sensing unit;

[0026] A voltage measuring unit, used to measure the voltage value (dVS) between the oxygen sensing unit and the common unit;

[0027] An internal resistance calculation unit, used to calculate the internal resistance (RPVS) of the oxygen sensing unit according to the formula RPVS=dVS / I_RPVS;

[0028] The charge balancing unit is used to provide a positive current pulse after the internal resistance calculation is completed to balance the charge of the oxygen sensing unit.

[0029] Furthermore, it also includes:

[0030] The atmosphere calibration unit is used to determine the relationship between the oxygen pump unit current and the oxygen value, which includes:

[0031] a calibration algorithm, stored in the microprocessor, for calibrating according to the current of the oxygen pump unit and the known oxygen value to establish a relationship between them;

[0032] The calculation unit is integrated in the microprocessor and is used to execute the calibration algorithm and calculate the oxygen value.

[0033] Furthermore, it also includes:

[0034] The communication interface is connected to the microprocessor and is used to output the calculated oxygen value to an external device via the RS485 communication protocol.

[0035] A method for measuring trace oxygen content uses the trace oxygen content measuring device to measure the trace oxygen content.

[0036] The method for measuring trace oxygen content is applied in reflow soldering or wave soldering.

[0037] The present invention has the following beneficial effects:

[0038] The device and method for measuring trace oxygen content of the present invention provide a high-precision and high-stability measurement solution, which is particularly suitable for inert reflow soldering furnaces and wave soldering furnaces with strict requirements on welding quality. The device calculates the oxygen concentration by measuring the current of the oxygen pump unit, and can achieve accurate measurement at the ppm level, ensuring the accuracy and stability of the measurement results over a long period of time. The microprocessor dynamically adjusts the current applied to the oxygen pump unit according to the comparison result between the voltage signal output by the oxygen sensing unit and the predetermined target value to maintain a stable voltage output and compensate for the influence of external environmental changes on the measurement results. This closed-loop control mechanism not only improves the measurement efficiency, but also reduces the measurement error caused by environmental fluctuations, and reduces the maintenance cost and replacement frequency of the sensor. Compared with the traditional electrochemical method, limiting current method and optical trace oxygen sensor method, the device of the present invention reduces the defective rate in production due to its stable output characteristics and long-term accuracy, improves production efficiency and product quality, and reduces the manufacturing cost of large-scale application. In addition, the device is less sensitive to environmental factors such as temperature and humidity, so that it can maintain reliable performance in various industrial manufacturing environments, and has significant social and economic benefits for improving the quality and reliability of welding processes.

[0039] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the overall framework diagram of the trace oxygen content measuring device according to the embodiment of the present invention;

[0041] Figure 2 A structural block diagram of an oxygen unit composed of an oxygen pump unit and an oxygen sensing unit according to an embodiment of the present invention;

[0042] Figure 3 This is a diagram of the temperature measurement results of the sensor according to an embodiment of the present invention;

[0043] Figure 4 Graph showing the relationship between the oxygen pump unit current and the oxygen value according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

[0045] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for fixing as well as for coupling or communication.

[0046] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0048] See also Figure 1 and Figure 2 An embodiment of the present invention provides a device for measuring trace oxygen content, including an oxygen pump unit, an oxygen sensing unit, a common electrode unit, a microprocessor, and a heating component. The oxygen pump unit promotes the oxidation-reduction reaction of oxygen on the zirconium oxide material inside the sensor through electrochemical reaction, and the generated current is positively correlated with the oxygen content in the actual environment; the oxygen sensing unit is used to detect the change of the oxygen content in the sensor environment caused by the oxygen pump unit inside the sensor; wherein, by measuring the potential difference related to the oxygen concentration, a voltage signal (VS) is output, which is proportional to the oxygen content inside the sensor; the common electrode unit (COM) provides a common electrical reference point for the oxygen pump unit and the oxygen sensing unit; the microprocessor receives the voltage signal (VS) of the oxygen sensing unit, compares the received voltage signal (VS) with a predetermined target value (e.g., 450mV), and adjusts the current applied to the oxygen pump unit according to the comparison result, so that the voltage signal (VS) reaches and maintains at the predetermined target value, forming a closed-loop control system; the predetermined target value is a voltage value corresponding to a specific oxygen content after calibration, so that when the voltage signal (VS) of the oxygen sensing unit is stable at the predetermined target value, it can accurately reflect the oxygen content in the external actual environment. The heating component is used to maintain the constant working temperature of the sensor.

[0049] In the present invention, the microprocessor accurately controls the operation of the oxygen pump unit according to the feedback signal of the oxygen sensing unit to achieve accurate measurement of the oxygen content; wherein the voltage signal (VS) reflects the change of the oxygen content in the internal environment of the sensor, and is used as a feedback signal to adjust the operation of the oxygen pump unit to maintain the stability of the oxygen content in the internal environment of the sensor. The current of the oxygen pump unit is generated by the electrochemical reaction caused by the oxygen content in the external environment, and the microprocessor in the present invention adjusts this current to maintain the stability of the output voltage of the oxygen sensing unit, compensate for the changes in the external environment, and improve the accuracy and stability of the measurement results. In this way, the sensor can accurately measure the oxygen content in the external environment and maintain high accuracy even in a dynamically changing environment.

[0050] See also Figure 1 and Figure 2 In a preferred embodiment, the microprocessor achieves precise regulation of the oxygen pump unit current through digital PID control to achieve a predetermined oxygen sensing unit voltage target value. The microprocessor adjusts the current of the oxygen pump unit through a PID control algorithm in response to changes in the oxygen content in the external environment. This adjustment ensures that the output voltage (VS) of the oxygen sensing unit can be maintained at a stable level even when the oxygen content in the external environment changes, thereby ensuring the accuracy and stability of the measurement results, and improving the accuracy of the measurement results by compensating for changes in the external environment.

[0051] In a preferred embodiment, the trace oxygen content measuring device further includes: a sampling resistor for measuring the voltage applied to the oxygen pump unit; and a current detection circuit for calculating the voltage drop through the sampling resistor and dividing it by the sampling resistor value to obtain a current signal representing the current value of the oxygen pump unit.

[0052] In a preferred embodiment, the trace oxygen content measuring device also includes: a temperature control unit, which is used to maintain a constant operating temperature of the sensor, and includes: a negative current pulse generator, which is used to input a negative current pulse (I_RPVS) into the oxygen sensing unit (VS); a voltage measuring unit, which is used to measure the voltage value (dVS) between the oxygen sensing unit (VS) and the common unit; an internal resistance calculation unit, which is used to calculate the internal resistance (RPVS) of the oxygen sensing unit (VS) according to the formula RPVS=dVS / I_RPVS; and a charge balancing unit, which is used to provide a positive current pulse after the internal resistance calculation is completed to balance the charge of the oxygen sensing unit (VS).

[0053] In a preferred embodiment, the trace oxygen content measuring device also includes: an atmosphere calibration unit, which is used to determine the relationship between the current of the oxygen pump unit and the oxygen value, which includes: a calibration algorithm, stored in a microprocessor, which is used to calibrate according to the current of the oxygen pump unit and the known oxygen value to establish a relationship between them; a calculation unit, integrated in the microprocessor, which is used to execute the calibration algorithm and calculate the oxygen value.

[0054] In some embodiments, the trace oxygen content measuring device further comprises a communication interface connected to the microprocessor for outputting the calculated oxygen value to an external device via the RS485 communication protocol.

[0055] The embodiment of the present invention further provides a method for measuring trace oxygen content, and uses the trace oxygen content measuring device to measure trace oxygen content.

[0056] The specific embodiments of the present invention are further described below.

[0057] Figure 1 The overall framework of the trace oxygen content measuring device of the embodiment of the present invention is shown. The trace oxygen content measuring device includes a sensor interface, an oxygen pump unit, an oxygen sensing unit, a common electrode unit, a heating component, an analog-to-digital converter, a microprocessor and an RS485 communication interface.

[0058] The trace oxygen measurement of the present invention adopts the zirconium oxide method. The zirconium oxide sensor includes an oxygen pump unit, an oxygen sensing unit, a common electrode unit and a heating component. When working, the sensor is accurately heated to make the sensor reach a stable temperature, and the oxygen change is reflected by the internal electrochemistry. The current of the oxygen pump unit is measured to calculate the oxygen concentration, which can be accurate to the ppm level. It has a stable output characteristic and can maintain the accuracy of the measurement result for a long time. The microprocessor accurately controls the temperature of the heating component of the sensor to keep the sensor at a constant temperature. External gas will pass through the diffusion hole of the sensor to the oxygen sensing unit and the oxygen pump unit. The output voltage of the oxygen sensing unit is used as a reference for the oxygen content of the external gas. The microprocessor changes the voltage output value of the oxygen sensing unit by changing the current applied to the oxygen pump unit, and controls the output value to a fixed value (such as 450mV). The output current on the oxygen pump unit is positively correlated with the oxygen content, and the microprocessor obtains the corresponding oxygen value through atmosphere calibration and specific calculation, and outputs the result through the RS485 communication interface of the microprocessor. The trace oxygen content measuring device can be used to measure the oxygen content during reflow soldering and wave soldering.

[0059] Figure 2 The block diagram of the oxygen unit composed of an oxygen pump unit and an oxygen sensing unit is shown. The oxygen unit control includes the following aspects: 1. The oxygen regulator uses the current or voltage of the oxygen pump unit IP1 to control the voltage value (VS) of the oxygen sensing unit, 2. Provide current to the oxygen sensing unit, 3. Generate and measure the RPVS pulse current.

[0060] The voltage value of the oxygen pump unit is controlled by the voltage applied to the oxygen pump unit through the digital PID to accurately control the oxygen reference pump voltage to reach the VS target value. The typical target value is 450mV. The voltage applied to the oxygen pump unit passes through a sampling resistor, and the current value is obtained by calculating the voltage drop of the sampling resistor and dividing it by the sampling resistor value. This current value represents the current value of the oxygen pump unit. The obtained current value of the oxygen pump unit is positively correlated with the actual oxygen value, and thus the oxygen value of the current environment can be accurately obtained.

[0061] Figure 3 The sensor temperature measurement results are shown. In order to accurately control the temperature of the sensor, an embodiment of the present invention provides feedback by measuring the internal resistance of the oxygen sensing unit (RPVS). A negative current pulse (I_RPVS) is input to the oxygen pump unit (VS), and then the voltage value (dVS) between the oxygen sensing unit and the common unit is measured. The internal resistance of the oxygen sensing unit is determined by the voltage generated by the current input to the oxygen sensing unit. The calculation method of the internal resistance (RPVS) of the oxygen sensing unit is: RPVS=dVS / I_RPVS, and the value of RPVS is calculated by the microprocessor cycle. After the calculation is completed, in order to balance the charge of the oxygen sensing unit, a positive current pulse needs to be provided to balance.

[0062] Figure 4 The relationship between the oxygen pump unit current and the oxygen value is shown in FIG. Figure 4 It can be seen that the oxygen pump unit current is positively correlated with the oxygen value, so the oxygen pump unit current can be used to represent the oxygen value. The relationship between the oxygen pump unit current and the oxygen value is determined by atmosphere calibration. The calibration relationship is calculated by the microprocessor. The obtained oxygen value is output through the RS485 communication interface of the microprocessor.

[0063] In summary, the trace oxygen content measurement device and method of the present invention provide a high stability and high accuracy oxygen content measurement solution, which is particularly suitable for applications such as inert reflow soldering furnaces and wave soldering furnaces that have strict requirements on welding quality. The oxygen sensing unit of the device detects the change in oxygen content in the sensor environment caused by the oxygen pump unit, and outputs a voltage signal proportional to the oxygen content. The microprocessor receives this voltage signal, compares it with the predetermined target value, and dynamically adjusts the current applied to the oxygen pump unit so that the voltage signal reaches and maintains the predetermined target value, forming a closed-loop control system. This mechanism not only ensures the accuracy and stability of the measurement results, but also improves the measurement efficiency and reduces the measurement error caused by environmental fluctuations by compensating for external environmental changes. Compared with the prior art, the device of the present invention has a longer service life, reduces the frequency and cost of replacing the sensor, and is suitable for large-scale applications. In addition, the addition of the heating component enables the sensor to work at a constant temperature, further improving the stability and accuracy of the measurement. The present invention overcomes the problems of the sensor being susceptible to environmental influences, reduced accuracy and high cost in the prior art, provides a low-cost, high-yield measurement method, significantly improves production efficiency and welding quality, reduces manufacturing costs, and has significant social and economic benefits.

[0064] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A device for measuring trace oxygen content, characterized in that: include: An oxygen pump unit, wherein the current generated by the oxygen pump unit is positively correlated with the oxygen content in the actual environment; An oxygen sensing unit, which is used to detect changes in the oxygen content of the sensor's internal environment caused by the oxygen pump unit; wherein, by measuring a potential difference related to the oxygen concentration, a voltage signal is output, and the voltage signal is proportional to the oxygen content in the sensor; a common electrode unit that provides a common electrical reference point for the oxygen pump unit and the oxygen sensing unit; a microprocessor, which receives the voltage signal of the oxygen sensing unit; compares the received voltage signal with a predetermined target value; and adjusts the current applied to the oxygen pump unit according to the comparison result so that the voltage signal reaches and is maintained at the predetermined target value, thereby forming a closed-loop control system; the predetermined target value is a voltage value corresponding to a specific oxygen content determined by calibration; Heating assembly, which is used to maintain the sensor's operating temperature constant.

2. The trace oxygen content measuring device according to claim 1, characterized in that: The microprocessor achieves precise regulation of the oxygen pump unit current through digital PID control to achieve a predetermined oxygen sensing unit voltage target value.

3. The trace oxygen content measuring device according to claim 1 or 2, characterized in that: The target value is 450 mV.

4. The trace oxygen content measuring device according to any one of claims 1 to 3, characterized in that: Also includes: A sampling resistor, used to measure the voltage applied to the oxygen pump unit; The current detection circuit is used to calculate the voltage drop through the sampling resistor and divide it by the sampling resistor value to obtain a current signal representing the current value of the oxygen pump unit.

5. The device for measuring trace oxygen content according to any one of claims 1 to 4, characterized in that: Also included is a temperature control unit for maintaining a constant operating temperature of the sensor, which includes: A negative current pulse generator, used for inputting a negative current pulse (I_RPVS) into the oxygen sensing unit; A voltage measuring unit, used to measure the voltage value (dVS) between the oxygen sensing unit and the common unit; An internal resistance calculation unit, used to calculate the internal resistance (RPVS) of the oxygen sensing unit according to the formula RPVS=dVS / I_RPVS; The charge balancing unit is used to provide a positive current pulse after the internal resistance calculation is completed to balance the charge of the oxygen sensing unit.

6. The device for measuring trace oxygen content according to any one of claims 1 to 5, characterized in that: Also included is an atmosphere calibration unit for determining the relationship between the oxygen pump unit current and the oxygen value, which includes: a calibration algorithm, stored in the microprocessor, for calibrating the oxygen pump unit based on the current and the known oxygen value to establish a relationship between the two; The calculation unit is integrated in the microprocessor and is used to execute the calibration algorithm to calculate the oxygen value.

7. The trace oxygen content measuring device according to claim 1, characterized in that: Also includes: The communication interface is connected to the microprocessor and is used to output the calculated oxygen value to an external device via the RS485 communication protocol.

8. A method for measuring trace oxygen content, characterized in that: The trace oxygen content measurement is performed using the trace oxygen content measurement device as claimed in any one of claims 1 to 7.

9. Application of the method for measuring trace oxygen content as claimed in claim 8 in reflow soldering or wave soldering.

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