A high temperature humidity measuring device

Abstract

The present invention relates to a high-temperature humidity measuring device, comprising an air circuit unit and a circuit unit; the air circuit unit comprises a gas filter, a venturi tube, a pressure regulating valve, and a humidity measuring cell; the gas filter is connected to the contraction section of the venturi tube, the pressure regulating valve is connected to the inlet section of the venturi tube, the diffusion section of the venturi tube is connected to the humidity measuring cell, a temperature sensor and a humidity sensor are provided in the humidity measuring cell, and the gas filter and the venturi tube are both heated by a heater; the circuit unit comprises an oscillation circuit, an analog-to-digital conversion circuit, and a processor; the temperature sensor is connected to the processor via the analog-to-digital conversion circuit, and the humidity sensor is connected to the processor via the oscillation circuit; the processor outputs a signal after software compensation calculation according to pre-set calibration parameters. The high-temperature humidity measuring device provided in the above technical solution can effectively solve the problems of existing high-temperature humidity measuring devices being greatly affected by the external environment and being unsuitable for high-temperature and corrosive working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature humidity measurement, and in particular to a high-temperature humidity measurement device. Background Art

[0002] The accuracy of high-temperature humidity measurement is a difficult problem in the field of metrology. Currently, common humidity measurement technologies include the chilled mirror method, the gravimetric method, the wet-dry bulb method, and electronic methods (such as the resistance method and the capacitance method). The chilled mirror method cools the semiconductor of the lens, lowering the temperature of the measurement chamber to below the humidity dew point, generating water mist on the lens surface. By measuring the mirror reflection characteristics through the optical path, the humidity dew point value can be accurately obtained, and other humidity values ​​can be obtained through conversion. It can be conveniently used for high-temperature measurements and has high accuracy. However, it can only test clean gases, and corrosion and small amounts of dust can cause inaccurate measurements. The gravimetric method uses high temperature to condense the humidity of the sample gas into liquid water through a cooler. The increase in weight of the liquid water per unit time is the weight increase of the humidity. Because weight has a high accuracy among existing measurement technologies, this method is often used in laboratories. In field measurements, flow control and weight can be affected by other factors, and the cost and complexity of this method are the limitations of this method. The dry-bulb method uses dry-bulb and wet-bulb temperature curves to determine the relative humidity of the gas being measured. This method is relatively inexpensive, but highly inaccurate. Factors such as flow rate, operation time, and operator input cannot be precisely controlled, leading to significant errors. Regarding electronic methods, most existing microelectronic sensor technologies are based on microelectronic materials such as glass, polymers, ceramics, and silicon, making them unsuitable for high-temperature and corrosive conditions. Therefore, a new technical solution is urgently needed to comprehensively address the challenges of existing technologies. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-temperature humidity measuring device, which can effectively solve the problems of existing high-temperature humidity measuring devices being greatly affected by the external environment and being unsuitable for high-temperature and corrosive working conditions.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A high temperature humidity measuring device comprises an air path unit and a circuit unit;

[0006] The gas circuit unit includes a gas filter, a venturi tube, a pressure regulating valve and a humidity measuring cell. The gas filter is connected to the contraction section of the venturi tube, the pressure regulating valve is connected to the inlet section of the venturi tube, the diffusion section of the venturi tube is connected to the humidity measuring cell, a temperature sensor and a humidity sensor are provided in the humidity measuring cell, and the gas filter and the venturi tube are heated by a heater.

[0007] The circuit unit includes an oscillation circuit, an analog-to-digital conversion circuit and a processor. The temperature sensor is connected to the processor via the analog-to-digital conversion circuit, and the humidity sensor is connected to the processor via the oscillation circuit. The processor outputs a signal after software compensation calculation according to pre-set calibration parameters.

[0008] The gas entering the gas filter is sample gas, and the gas entering the pressure regulating valve is instrument gas; the instrument gas is compressed air or high-purity nitrogen.

[0009] The measurement formula for humidity is:

[0010]

[0011] The humidity value of the mixed gas measurement is the humidity value of the mixed gas of the sample gas and instrument gas after passing through the Venturi tube.

[0012] Preferably, the temperature sensor is a platinum resistance.

[0013] In the high-temperature humidity measuring device provided in the above technical solution, the sample gas enters the heated gas filter through the gas path inlet, and then enters the venturi tube heated by the heater; at the same time, the instrument gas is pressure-regulated by the pressure regulating valve, and the heated venturi tube generates a negative pressure, which draws the sample gas entering the venturi tube. The humidity of the gas at the outlet of the venturi tube is reduced by 50 to 100 times, and the humidity is controlled at 500 to 3000 ppm. The gas obtained after mixing is measured by the temperature sensor and humidity sensor in the humidity measuring cell. The temperature sensor is connected to the processor through an analog-to-digital conversion circuit. At the same time, the humidity sensor generates a frequency signal through an oscillation circuit and transmits the frequency signal to the processor. The processor calculates the final humidity value according to the pre-set calibration parameters and software compensation.

[0014] The high-temperature humidity measuring device of the present invention utilizes a gas mixing device to proportionally reduce the humidity value of high-temperature (above 150 degrees Celsius) and high-humidity (0-40% v / v) gas to a normal-temperature, non-condensing state. This eliminates the need for full-process heating and gas pretreatment using traditional gas sampling methods, reduces structural complexity, avoids damage to the equipment caused by high temperature and corrosion, and thus significantly reduces costs. A pressure regulating valve and a heater are used to control gas concentration, which is simple, convenient, and easy to control. Furthermore, a platinum resistor is used as the temperature sensor, and a mirror image constant current source is used to provide an excitation signal to the platinum resistor, thereby eliminating ambient temperature interference. Finally, testing has shown that the measurement accuracy of the high-temperature humidity measuring device can meet a relative error of reading*20%, which can basically meet the needs of most current online high-temperature humidity measurement applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a system structure diagram of the high temperature and humidity measuring device of the present invention;

[0016] Figure 2 This is the analog-to-digital conversion circuit diagram;

[0017] Figure 3 This is the circuit diagram of the mirror constant current source;

[0018] Figure 4 This is the oscillation circuit diagram.

[0019] In the figure: 1. Gas inlet; 2. Gas filter; 3. Heater; 4. Temperature sensor; 5. Circuit unit; 6. Exhaust interface; 7. Humidity sensor; 8. Humidity measuring cell; 9. Venturi tube; 10. Pressure regulating valve; 11. Instrument gas inlet. DETAILED DESCRIPTION

[0020] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following examples. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection of the present invention.

[0021] The technical solution adopted by the present invention is as follows Figures 1 to 4 As shown, a high-temperature humidity measuring device includes an air circuit unit and a circuit unit 5; the air circuit unit includes a gas filter 2, a venturi tube 9, a pressure regulating valve 10 and a humidity measuring cell 8. The sample gas enters the gas filter 2 from the air circuit inlet 1 and then enters the contraction section of the venturi tube 9 (specific ratio: 10-100). The instrument gas (compressed air or high-purity nitrogen) passes through the instrument gas inlet 11 and the pressure regulating valve 10. After passing through the inlet section of the venturi tube 9, the mixed gas enters the humidity measuring cell 8 through the outlet of the venturi tube 9. The outlet pipeline of the humidity measuring cell 8 is connected to the emptying interface 6. A temperature sensor 4 (a platinum resistor) and a humidity sensor 7 are provided in the humidity measuring cell 8. The gas filter 2 and the venturi tube 9 are both kept above the condensation temperature of the sample gas by the heater 3. The above-mentioned temperature sensor 4 uses a platinum resistor, and uses a mirror constant current source to provide an excitation signal to the platinum resistor, thereby eliminating ambient temperature interference.

[0022] The circuit unit 5 includes an oscillating circuit, an analog-to-digital conversion circuit and a processor. The temperature sensor 4 is connected to the processor via the analog-to-digital conversion circuit. Figure 2 and Figure 3 , the output voltage terminal V of the mirror constant current source circuit out Connect AD3 of the processor MCU, and the processor MCU obtains the output voltage terminal V out The voltage value is I=V out / Ra can obtain the constant current source current value I, and the constant current source drives the platinum resistor PT; the analog-to-digital conversion circuit converts the resistance value of the temperature sensor 4 that changes with temperature into a measurable voltage signal, and the processor MCU obtains the AD1 terminal voltage as U1, and the AD2 terminal voltage as U2, then the voltage value across the temperature sensor 4 is U=U1-U2; the measured voltage signal is data processed, and the resistance value of the platinum resistor can be obtained as U / I, and then the high-precision temperature change value is obtained by looking up the table.

[0023] The humidity sensor 7 is connected to the processor through an oscillation circuit. Figure 4 After power is applied, VCC charges humidity sensor C through R1 and R2. When the voltage Vc across C rises to 2VCC / 3, Vo outputs a low level, and C begins to discharge through R2 and chip IC1. When Vc drops to VCC / 3, Vo outputs a high level, and VCC charges humidity sensor C through R1 and R2. This cycle repeats, forming an oscillator circuit, generating a frequency signal Vo, which is transmitted to the processor. The processor then calculates and outputs a signal based on pre-set calibration parameters after software compensation. Humidity sensor 7 can measure humidity within the range of room temperature accuracy, and high-precision temperature conversion can be used to achieve high accuracy.

[0024] The measurement formula for humidity is:

[0025]

[0026] The humidity value of the mixed gas measurement is the humidity value of the mixed gas of the sample gas and instrument gas after passing through the Venturi tube.

[0027] In summary, the high-temperature humidity measuring device provided by the present invention uses high-purity nitrogen or compressed air to dilute the sample gas concentration by 50 to 100 times, and uses a heater to reduce the humidity temperature to below the dew point at room temperature. Then, a traditional humidity capacitance measurement method is used for measurement, which avoids damage to the equipment caused by high temperature and corrosion, and can effectively extend the service life of the equipment and measurement accuracy. At the same time, after testing, the accuracy of the high-temperature humidity measuring device can meet the relative error of reading*20%, which can basically meet the most current applications of online high-temperature humidity measurement.

[0028] The above describes the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. After knowing the contents described in the present invention, ordinary technicians in this technical field can make several equivalent changes and substitutions without departing from the principles of the present invention. These equivalent changes and substitutions should also be regarded as falling within the scope of protection of the present invention.

Claims

1. A high temperature humidity measuring device, characterized in that: It includes a gas circuit unit and a circuit unit; The gas circuit unit includes a gas filter, a venturi tube, a pressure regulating valve and a humidity measuring cell. The gas filter is connected to the contraction section of the venturi tube, the pressure regulating valve is connected to the inlet section of the venturi tube, the diffusion section of the venturi tube is connected to the humidity measuring cell, a temperature sensor and a humidity sensor are provided in the humidity measuring cell, and the gas filter and the venturi tube are heated by a heater. The circuit unit includes an oscillation circuit, an analog-to-digital conversion circuit, and a processor. The temperature sensor is connected to the processor via the analog-to-digital conversion circuit, and the humidity sensor is connected to the processor via the oscillation circuit. The processor outputs a signal after software compensation calculation based on pre-set calibration parameters. Among them, the temperature sensor uses a mirror constant current source to provide an excitation signal, and the output voltage end of the mirror constant current source circuit is Connect AD3 of the processor MCU, and the processor MCU obtains the output voltage terminal The voltage value is You can get the constant current source current value , a constant current source drives the platinum resistor PT; the analog-to-digital conversion circuit converts the resistance value of the temperature sensor that changes with temperature into a measurable voltage signal. The processor MCU obtains the voltage at the AD1 terminal as U1 and the voltage at the AD2 terminal as U2. The voltage value at both ends of the temperature sensor is U=U1-U2; the measured voltage signal is processed and the resistance value of the platinum resistor can be used Obtain, and then look up the table to obtain high-precision temperature change values; The humidity sensor is connected to the processor through an oscillation circuit. After the power is turned on, VCC charges the humidity sensor C through R1 and R2. When the voltage Vc across C rises to 2VCC / 3, Vo outputs a low level. At this time, C begins to discharge through R2 and chip IC1. When Vc drops to VCC / 3, Vo outputs a high level. VCC charges the humidity sensor C through R1 and R2. This cycle repeats to form an oscillation circuit, generate a frequency signal Vo, and transmit the frequency signal Vo to the processor.

2. The high temperature and humidity measuring device according to claim 1, characterized in that: The gas entering the gas filter is sample gas, and the gas entering the pressure regulating valve is instrument gas.

3. The high temperature and humidity measuring device according to claim 2, characterized in that: The instrument gas is compressed air or high-purity nitrogen.

4. The high temperature and humidity measuring device according to claim 3, characterized in that: The measurement formula for humidity is: ； The humidity value of the mixed gas measurement is the humidity value of the mixed gas of the sample gas and instrument gas after passing through the Venturi tube.

5. The high temperature and humidity measuring device according to claim 1, characterized in that: The temperature sensor is a platinum resistance.

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