GB/T 11605-2026Methods of humidity measurement (English PDF)

4.4.1 Measurement Preparation and Precautions

4.4.1.1 The hygrometer should be suspended vertically on the bracket or fixed to the bracket, and the bracket base should be kept horizontal.

4.4.1.2 The wind speed at the installation site should not exceed

0.2 m/s, and the temperature should not exceed 45°C.

4.4.1.3 The humidity-sensitive material of the hygrometer should be kept clean.

4.4.1.4 If the hygrometer has been stored in an environment with a relative humidity below 10% for an extended period, it should be placed in an environment with a relative humidity greater than 95% before use. It must be restored to environmental conditions and calibrated before it can be used.

4.4.2 Measurement Method Observe the readings by marking the position of the recording curve with the pointer or pen tip.

4.4.3 Measurement Results Read the value as half of the smallest division of the hygrometer.

4.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

4.6 Test Report The test report is attached as Appendix A.

5.4.1 Measurement Preparation and Precautions

5.4.1.1 The wet bulb should be wrapped with special gauze (or cotton gauze sleeve), with only one layer of gauze. The overlapping part should not exceed 1/3 of the bulb's circumference. Tie the cotton yarn from the gauze at both ends, as shown in Figure

2.The wrapped gauze should fit snugly against the ball without any wrinkles. Figure

2.Schematic diagram of the wet-bulb and dry-bulb test.

5.4.1.2 The ventilation humidifier should be hung vertically on the bracket.

5.4.1.3 The installation location should be free from direct sunlight or other sources of heat radiation.

5.4.1.4 When wet-bulb gauze becomes contaminated, it should be replaced.

5.4.1.5 The gas sample should not contain impurities, oil, or other destructive components.

5.4.1.6 When the gas sample is a toxic or harmful gas, the waste gas should be properly treated or recycled.

5.4.2 Measurement Method

5.4.2.1 Thoroughly wet the wet bulb gauze with distilled water and start the ventilator. When using a mechanical ventilator, the spring must be fully wound in one go.

5.4.2.2 Take readings 2 minutes after the ventilator has been running. First read the wet-bulb temperature, then the dry-bulb temperature, and record the atmospheric pressure simultaneously. Repeat this process if necessary. Take the readings according to the instruction manual.

5.4.3.1 Calculation Method

5.4.3.2 Table Lookup Method Using the obtained dry-bulb temperature, wet-bulb temperature, and atmospheric pressure, find the required relative humidity in the humidity lookup table provided with the hygrometer. Humidity value; you can also refer to C.2 to find the humidity value in other units (the same applies to the other methods).

5.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

5.6 Test Report The test report is attached as Appendix A.

6.4.1 Measurement Preparation and Precautions

6.4.1.1 The instrument employs an induction sampling method. Sampling points should be located in positions sufficient to obtain representative gas samples and should be taken from nearby locations. Typical The sampling system flowchart is shown in Figure 4.

6.4.1.2 The sampling valve shall be a needle valve with a small dead volume. The sampling pipeline shall be made of stainless steel with a length not exceeding 2m and an inner diameter of 2mm~4mm. Pipes, including copper pipes and PTFE pipes with a wall thickness of not less than 1 mm, etc. The inner wall of the pipes should be smooth and clean; pipes made of highly elastic materials should not be used. Such as rubber hoses, polyvinyl chloride hoses, etc.

6.4.1.3 Increasing the total sampling flow rate and setting up a bypass gas path before the gas sample enters the instrument are effective ways to improve measurement accuracy and shorten measurement time. Effective approach.

6.4.1.4 The ambient temperature should be at least 5°C higher than the gas sample dew point temperature; otherwise, the entire sampling system and the gas path system of the instrument exhaust port must be checked. Take measures to raise the temperature to avoid changes in the humidity of the gas sample or blockage of the pipeline due to condensation.

6.4.1.5 After connecting the gas line, check the airtightness of the gas line.

6.4.1.6 If the platinum resistance temperature sensor lacks an automatic compensation function for surface contamination errors, or if the surface contamination is severe, an appropriate solvent should be applied. The agent was used for manual cleaning.

6.4.1.7 If the gas sample contains other gaseous impurities that condense before water vapor (such as certain hydrocarbons), or if the gas sample contains substances that can condense with water... Condensed substances (such as methanol) should be separated.

6.4.1.8 When the dew point is between -20°C and 0°C, the condensation on the surface of the platinum resistance temperature sensor may be either frost or dew (supercooled water). At this point, the visual dew point meter should be carefully observed with the aid of a microscope to distinguish between the two.

6.4.1.9 The gas sample should not contain particulate matter, oil, or other destructive components. The inlet filter should be cleaned regularly to maintain the gas path. Clean and unobstructed.

6.4.1.10 When the gas sample is a toxic or harmful gas, the waste gas should be properly treated or recycled.

6.4.2 Measurement Method

6.4.2.1 The instrument operation procedure shall be performed in accordance with the instruction manual.

6.4.2.2 Based on the structure of the sampling system and the humidity of the gas sample, the gas path system is subjected to different flow rates and durations using the gas to be measured. The air is blown and rinsed to ensure the accuracy of the measurement results.

6.4.3 Measurement Results Read the instrument reading directly.

6.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

6.6 Test Report The test report is attached as Appendix A.

7.4.1 Measurement Preparation and Precautions

7.4.1.1 Place the sensor directly into an appropriate part of the gas to obtain a representative humidity value.

7.4.1.2 The moisture-sensing part of the humidity-sensitive element should not be touched by hand and should be protected from contamination, corrosion or condensation.

7.4.1.3 When used in dusty environments, an outer cover or filter should be installed.

7.4.1.4 The instrument should be calibrated in a timely manner according to the instrument instruction manual. When the instrument has no temperature compensation, the calibration temperature should be close to the operating temperature.

7.4.1.5 It should not be used for extended periods in gases with relative humidity close to 100%.

7.4.1.6 The gas sample should not contain impurities, particulate matter, oil, or other destructive components.

7.4.1.7 When the gas sample is a toxic or harmful gas, the exhaust gas should be properly treated or recovered.

7.4.2 Measurement Method The instrument operation procedure should be followed according to the instruction manual.

7.4.3 Measurement Results Read the value after the instrument reading stabilizes.

7.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

7.6 Test Report The test report is attached as Appendix A.

8.4.1 Measurement Preparation and Precautions

8.4.1.1 Connect the instrument and pipelines according to the instructions for use, and ensure that the pipelines are airtight.

8.4.1.2 When the gas sample conditions change, the flow meter should be recalibrated.

8.4.1.3 When the sample is a bottled/canned or bagged gas, the humidity increases as the bottle pressure decreases; therefore, it should be stored near the level specified by the gas manufacturer. Sampling under pressure.

8.4.1.4 The gas sample should not contain impurities, particulate matter, oil, or other destructive components.

8.4.1.5 When the gas sample is a toxic or harmful gas, the exhaust gas should be properly treated or recovered.

8.4.2 Measurement Method

8.4.2.1 When the instrument is purged with dry nitrogen gas and electrolyzed simultaneously, and the reading changes continuously for 20 minutes without exceeding 1 µL/L, the reading is considered valid. This is the instrument's background value.

8.4.2.2 Adjust the gas flow rate according to the instruction manual (usually 100 mL/min), and adjust the bypass flow rate to approximately 1 L/min. Once the instrument reading stabilizes... Read the value after setting.

8.4.3 Measurement Results The humidity value of the gas sample is calculated by subtracting the background value from the instrument reading, according to formula (4).

8.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

8.6 Test Report The test report is attached as Appendix A.

9.4.1 Measurement Preparation and Precautions

9.4.1.1 Clean and dry the absorption tube.

9.4.1.2 Calibrate the flow meter.

9.4.1.3 When filling with desiccant, clean gloves should be worn and the operation should be carried out in a dedicated glove box. During the filling process, glass fibers or similar materials should be added. The packing material should be used to reduce the resistance of the absorption tube, and the operation should be rapid.

9.4.1.4 After filling, immediately clean the glass ground joint of the absorber tube (if powder enters the side tube, it should also be cleaned), apply a small amount of vacuum grease, and seal.

9.4.1.5 When starting and stopping aeration absorption, attention should be paid to the pressure balance of the gas path to prevent the spraying of phosphorus pentoxide powder. If powder spraying occurs, Remove the absorbent tube and clean it. Repeat steps

9.4.2.1 and thereafter.

9.4.1.6 Determine the appropriate absorption amount according to the measurement accuracy requirements, and determine the absorption time according to the humidity of the gas sample.

9.4.1.7 The gas sample should not contain impurities, oil, or other destructive components.

9.4.1.8 When the gas sample is a toxic or harmful gas, the waste gas should be properly treated or recycled.

9.4.2 Measurement Method

9.4.2.1 Accurately weigh the absorption tube using a precision balance and record the mass.

9.4.2.2 Connect the absorption tube to the system. Switch the two three-way valves to allow the gas sample to purge the sampling system through the bypass tube at the selected flow rate for several hours.

9.4.2.3 Switch the three-way valve and simultaneously open the stopcock of the absorption tube to allow the gas sample to pass through the absorption tube at the selected flow rate, and record the ambient temperature and atmospheric temperature. Parameters such as pressure, absorption time, and flow rate.

9.4.2.4 Switch the three-way valve and quickly close the absorber tube stopcock, remove the absorber tube, weigh accurately again and record the result.

9.4.3 Measurement Results Calculate according to formula (5) in 9.2.

9.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

9.6 Test Report The test report is attached as Appendix A.

10.4 Measurement Procedure

10.4.1 Measurement Preparation Add approximately 150 mL of anolyte to the titration cell, and add catholyte to the cathode cell until the liquid level is approximately equal to that of the anolyte in the titration cell. Connect the instrument to the power supply, plug the air inlet with a stopper, and adjust the magnetic stirrer to the speed setting where the anolyte just doesn't bubble. Turn on the instrument. The electrolysis (titration) function reacts the water in the titration cell. When the reaction rate of water displayed by the instrument is below 0.30 µg/s, the titration begins. Measurement.

10.4.2 Instrument Calibration Draw 0.5 µL of pure water using a microsyringe, press the start button, and inject it into the titration cell through the PTFE injection plug to calibrate the instrument. The instrument reading error shall not exceed ±5%.

10.4.3.1 Gas sampling. Performed in accordance with the provisions of

7.10 in GB/T 6681-2003.

10.4.3.2 Weigh the gas sampling cylinder and the gas sample using an electronic balance.

10.4.3.3 Connect the gas sampling cylinder to the instrument's inlet as shown in Figure 9, press the instrument's start button, and slowly open the gas valve. The outlet valve of the gas sampling cylinder is used to regulate the gas flow as continuous and uniform bubbles through the reagent in the titration cell. Index number explanation. 1

---Gas sampling cylinder; 2

---Pressure gauge. Figure

9.Schematic diagram of Karl Fischer moisture analyzer connected to gas sampling cylinder.

10.4.3.4 After introducing the gas for a period of time, close the outlet valve of the gas sampling cylinder, wait for the instrument's titration reaction to reach its endpoint, and then read the instrument reading. The instrument displays the measured moisture content.

10.4.3.5 Remove the gas sampling cylinder and weigh the gas sampling cylinder and the remaining gas sample using an electronic balance.

10.4.3.6 Input the mass difference between the gas sampling cylinder weighed before and after the injection into the instrument.

Note. If the gas flash evaporator method and the volumetric flow meter method are used, the measurement method is shown in Appendix D.

10.4.4 Measurement Results After the instrument reading stabilizes, take the reading and calculate the water content according to formula (6).

10.5 Precision Perform in accordance with the provisions of GB/T 6379.2.

10.6 Measurement Report The test report is attached as Appendix A.