What are the factors affecting the accuracy of ultraviolet radiation luminometer measurement results?

In daily use, there are many factors that affect the accuracy of the measurement results of the ultraviolet radiation illuminance meter. If it is used improperly, even a qualified instrument will produce large errors, which will bring unnecessary trouble to the enterprise or testing work. Therefore, the following issues should be paid attention to when using a UV illuminance meter to measure UV irradiance:

1. The influence brought by the verification device of the ultraviolet radiation illuminance meter

The ultraviolet irradiance meter used by the enterprise must be sent to the local metrology department for metrological verification every year. During the verification process, the verification device of the ultraviolet illuminance meter will bring certain influences, including the influence of the value transfer of the superior level, the influence of the instability of the standard ultraviolet illuminance meter, and the uncertainty of the verification device of the standard ultraviolet illuminance meter. . Some of the above uncertainties are given by the upper level, some are measured, and some errors caused by influences are systematic errors. The uncertainty of ultraviolet radiation illuminometers in different bands is different. At present, the measurement uncertainty given by the National Institute of Metrology of CHINA is U=3.3-%-3.9% (k=1).

2. The influence of the measurement repeatability of the tested ultraviolet illuminance meter

Under the irradiation of a uniform and stable ultraviolet light source, the ultraviolet illuminance meter repeatedly measures the irradiance 10 times, and calculates the average value and standard deviation. The uncertainty caused by the repeatability of a better ultraviolet irradiance meter is about 1%.

3. The influence brought by the installation and adjustment of the inspected ultraviolet radiation illuminance meter

In the process of verifying the ultraviolet illuminance meter, the ultraviolet illuminance meter should be installed on the optical track, and adjusted so that the geometric center of the ultraviolet illuminance meter probe is coaxial with the optical center of the light source, and the plane of the ultraviolet illuminance meter probe is perpendicular to the optical axis. In the experiment, the UV illuminance meter is usually installed 10 times, and the standard deviation is calculated, and the uncertainty is about 1%.

4. The influence of the instability of the ultraviolet light source

The stability of ultraviolet light sources in different bands is different. For example, the stability of low-pressure mercury lamps is better, and the stability of black light high-pressure mercury lamps is worse than that of low-pressure mercury lamps. The newly purchased ultraviolet light source must first be aged, and the stability of the aged ultraviolet light source is better. Before each use, ignite the UV light source to preheat, at least 20 minutes before the UV light source can be stabilized. When measuring the black light high-pressure mercury lamp, it is usually measured every 10 minutes, and the variation within 1 hour is about 5%.

5. The influence of the inhomogeneity of the irradiation surface of the ultraviolet light source

The UV-A ultraviolet light source we use, that is, the black high-pressure mercury lamp, is produced in the United States, and its radiation surface is circular; the UV-B ultraviolet light source, that is, the low-pressure mercury lamp, is produced by the CHINA Institute of Metrology, and its radiation surface is rectangular . The inhomogeneity of the ultraviolet light source has a great influence on the measurement. Usually take the optical axis as the center, measure at a distance of 20mm from the optical axis up, down, left, and right, and record the maximum change.

6. The impact of the inconsistent cosine performance of the standard UV illuminance meter and the tested UV illuminance meter

The cosine performance of UV illuminance meters produced by different manufacturers is different, which will have a certain impact on the measurement results. Therefore, firstly, adjust the light-emitting surface of the UV light source and the light-receiving surface of the receiver so that they are perpendicular to the optical axis, and the center is located on the measurement optical axis, and adjust the distance between the receiver and the light source, which is more than 10 times greater than the light-emitting surface of the light source. Adjust the diaphragm so that it does not block the light from the UV source to the receiver. Rotate the receiver left and right, measure 0 degrees, 1 to 10 degrees, -1 to -10 degrees, with 1 degree as the interval, measure the indicated value, use the cosine law to calculate the theoretical values ​​of the above points and calculate the error.

7. The impact of the inconsistency of the spectral response between the standard UV illuminance meter and the tested UV illuminance meter

The spectral response of the standard UV illuminometer and the tested UV illuminometer is inconsistent, which has a great impact on the measured value. This requires a Spectrophotometer to measure the spectral curves of the standard UV illuminometer and the tested UV illuminometer. and determine its impact.

The above are the main influencing factors, and there are more influencing factors that will not be elaborated one by one.