Photoelectric direct reading spectrometer is a rapid quantitative analysis instrument for the analysis of ferrous metals and non-ferrous metals. This instrument is widely used in metallurgy, machinery and other industrial sectors, to carry out online analysis before the smelting furnace and product inspection in the central laboratory, is one of the effective means to control product quality.
What are the seven factors that affect the analysis quality of direct reading tube spectrometer

1. Argon
The main function of argon blowing is to drive away the air in the spark chamber and reduce the absorption of the air to the spectral line in the ultraviolet region. Mainly because the oxygen and water vapor in the air have a strong absorption band in the far ultraviolet region, which has a great impact on the analysis results, and is not conducive to the excitation stability, the formation or strengthening of diffusion discharge, and the white spot is generated during excitation. Therefore, the purity of argon must be required to reach 99.996% or more. In addition, the pressure and flow rate of argon also have a certain impact on the analysis quality, which determines the impact ability of argon on the discharge surface. This excitation ability must be appropriate, too low, not enough to wash away the oxygen generated during the sample excitation process and the oxides formed by it, which agglomerate on the electrode surface, thus inhibiting the continued excitation of the sample. Too large, one is to cause unnecessary waste. Second, it also has certain damage to the spectrometer. Therefore the argon pressure and flow rate must be appropriate. According to practice, the pressure and flow of argon should be adjusted according to different materials, for the analysis of low and medium alloy steel, the input of the spectrometer argon pressure should reach 0.5-1.5mpa, the dynamic argon flow is 12 to 20 readings, and the static argon flow is 3 to 5 readings.

2. Slit
The spectrometer uses a complex and sensitive optical system. The ambient temperature, humidity, mechanical vibration, and atmospheric pressure changes of the spectrometer will cause the spectral line to produce small changes and cause the spectral line to shift. Changes in air pressure and humidity will change the refractive index of the medium, thereby making the spectral line offset, the increase in humidity will not only increase the refractive index of the air, but also have a corrosive effect on the optical parts, reduce the transmittance of the instrument, the humidity should generally be controlled below 55%-60%. The effect of temperature on the grating mainly changes the grating constant, the role dispersion changes, and the spectral line shifts. These changes will cause the spectral lines not to align with the corresponding exit slit, thus affecting the analysis results. Therefore, the optical system is adjusted at least once a day, if the indoor temperature control is constant. Adjust the slit twice a week, even if the weather doesn’t change much.

3. Entrance window lens
The lens leading to each chamber, especially the lens leading to the air chamber, blows argon when the sample is excited, so that the dust generated when the sample is exposed is blown onto the lens and prevents the light from passing through, affecting the accuracy of the determination results. Therefore, it should be cleaned frequently, generally twice a week, to keep it clean and ensure that all light enters the light chamber through the lens for determination. In particular, it is necessary to stimulate several waste samples after cleaning the lens, and then carry out standardized operations after the strength is stable, otherwise the analysis quality will be affected.

4. Excitation station
Cleaning the inner surface of the excitation platform is mainly to avoid the residual dust discharge on the inner wall affecting the analysis results. Usually every 100-200 excitation should be cleaned once. The distance between the electrode and the excitation surface must be adjusted according to the requirements of the pole distance, if the distance from the excitation surface is too large, the sample is not easy to excite, if the distance between the electrode and the excitation surface is too small, the discharge current during exposure is too large, so that it does not match the parameters of the instrument, so that there are differences between the measurement results and the actual results, affecting the accuracy of the measurement. Therefore, the distance between the electrode and the excitation surface must be adjusted accurately, and this problem must be paid attention to after cleaning the excitation table and electrode.

5. Correction of working curve
Although the photoelectric direct reading spectrometer method is not limited by the photosensitive plate, the working curve will change after a period of time after being drawn. For example: contamination of the lens, contamination of the electrode, changes in temperature and humidity, the influence of argon, fluctuations in the power supply, etc., can make the curve change. Where A was in the original graph, after a period of time, the curve may drift to B. In order to use curves for analysis one must try to restore curve B to the position of curve A. For this reason, the working curve must be standardized. The following points must be noted in curve standardization:
(1) After cleaning the sample excitation platform, it must be excited for more than 10 times or through argon for an hour before doing daily standardization work.
(2) The standardized sample should be uniform, the sample preparation should be careful, the surface of the sample is smooth, and the grain is clear. Analytical clearance is accurate and the sample holder is kept clean.
(3) The frequency of standardization is determined according to the number of samples analyzed, and generally it must be standardized twice a day.

6. Control the sample
In actual work, due to the metallurgical process and some physical differences between the sample and the standard sample, the working curve is often changed, usually the standard sample is mostly forging and rolling state, and the daily analysis is the casting state. In order to avoid the influence of the sample on the analysis result due to the change of the metallurgical state, a control sample with the same metallurgical and physical state of the analysis sample should often be used to control the analysis result. The element content of the control sample should be within the content range of the working curve, and the content of the analysis sample should be as close as possible. At the same time, the element content of the controlled sample should be accurate and reliable, the composition is evenly distributed, and the appearance is free from physical defects such as pores, sand holes, and cracks.

7. Sample
The quality of the spectral analysis results depends largely on the sample, and attention should be paid to the preparation and treatment technology of the sample. The quality of the analysis is greatly affected by the error caused by stomatal segregation when the surface is not flat or the sample is not well placed. Therefore, sample processing must meet the following requirements:
(1) The entire surface of the sample should be uniform (its shape and size are suitable for the excitation table so that the gas flushing chamber can be sealed).
(2) No trachoma.
(3) Clean the rust and oil on the back of the sample to ensure good contact between the sample and the excitation table.
(4) The surface of the sample should not be contaminated, and the grinding sample should have a grain.
(5) When the sample is excited, the excitation point is generally located at 1/2 of the sample radius, where the chemical composition is relatively uniform, and the result has a representative degree and the determination accuracy is high. In summary, through many years of practice, several factors affecting direct reading spectrometry are summarized, which have important application value to improve the quality of elemental analysis.