《GB/T 5832.1-2003 Gas Humidity Measurement Part 1 Electrolysis Method》
GB/T 5832.1-2003 Gas Humidity Measurement Part 1 Electrolysis Method
1. Scope
This part of GB/T 5832 is applicable to the measurement of humidity in a saturated or partially saturated non-corrosive gas by electrolysis method, as an alternative to the various wet and dry gas hygrometers.
2. Normative References
The following normative documents contain provisions which, through reference in this GB/T 5832.1 section, constitute provisions of this standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the document referred to applies.
GB/T 2423.1-2008 Environmental testing for electric and electronic products Part 1: General and guidance
3. Terms and Definitions
For the purpose of this part of GB/T 5832, the following terms and definitions apply.
3.1
Electrolysis method
Gas humidity measurement based on the diffusion of oxygen or hydrogen created by galvanic action of an anode immersed in an electrolyte in a closed environment
3.2
Working temperature
The temperature range over which the reagents included in the ell give reliable results
3.3
Reagents
The electrolytes, or combination of electrolytes, used in the measurement system
4. Principle
The basic principle of the electrolysis method is to dissolve oxygen (or hydrogen) from an electrolyte in a cell in the presence of an external electrical current, and the oxygen (or hydrogen) then diffuses into the gas. The rate of electrolysis is a true measure of the relative humidity of the gas, since the diffusion rate of the gas equals the electrolysis rate.
5. Apparatus
5.1
Reagents
Potassium bromide (KBr) or potassium chloride (KCl) are commonly used as the solvents for this method. However, other electrolytes may also be used.
5.2
Cell
The cell should be constructed with a stainless steel or aluminum body, in the form of a small, sealed cylindrical vessel, and should contain a volume of electrolyte sufficient to completely fill the vessel. The cell should be provided with two leads connected to the anode and cathode respectively.
5.3
Electrical power supply
The electrolysis reaction is started by the application of electrical power to the anode and cathode electrodes in the cell. The power supply should be sufficient to provide a current equal to the amount of diffused gas divided by the diffusion time. Voltage may be varied to control current.
6. Procedure
6.1
Preparation
The electrolyte should be thoroughly mixed before pouring it into the cell, and should be kept stirred with a strong magnet after filling the cell.
6.2
Conditioning
The cell should be left undisturbed with the stopper in place, for a period of time prior to measurement sufficient to allow the electrolyte to reach thermal equilibrium with the gas surrounding the cell.
6.3
Glazing
The external surface of the cell should be sealed with a glass covering to minimize any evaporation or convection of gas into or out of the cell.
6.4
Measurement
The electrolysis process is initiated by the application of an electrical current to the anode and cathode electrodes. The current should be applied in such a way that the total amount of gas diffused through the glazing is equal to the amount of oxygen (or hydrogen) produced by the electrolysis.
6.5
Calibration
The cell should be calibrated against a known wet-and-dry hygrometer, such as a combination wet-and-dry hygrometer (Drybulb 847), or an accurately calibrated psychrometer.
7. Uncertainty
The uncertainty of measurement for relative humidity using this method is typically + 1.5 %RH.
8. Quality Assurance
In order to ensure the accuracy and reproducibility of the results, it is recommended that a quality assurance program be implemented. This quality assurance program should include measurement of dry-bulb temperatures, frequent calibration of the analytical instrument and measurements of the reference standards, as well as calibration of the reference standards against a certified psychrometer.
9. Results
The results of the measurement should be expressed in terms of relative humidity.
10. Test Report
The test report should include the following information:
a) Name of laboratory;
b) Test sample;
c) Test conditions;
d) Test results and related information;
e) Equation used for calculation;
f) Uncertainty of measurement;
g) Description of the quality assurance program.
