Examples of UV-Visible Spectrometers in Absorbance Applications

UV-visible fiber spectrometer

Spectroscopic instruments are an important part of optical instruments. They are basic equipment that apply optical principles to measure, analyze and process the structure and composition of substances. They have the advantages of high analytical accuracy, large measurement range, and fast speed. Ordinary spectrometers It can only detect the visible light band with a wavelength of 400-800nm, but in some special fields, it is necessary to detect the ultraviolet light band with a wavelength of 200-400nm.

Currently, most micro-UV spectrometers on the market use back-thinned or coated CCDs as photosensitive elements, which are relatively expensive. Therefore, this paper proposes a design scheme for applying cost-effective CMOS sensor chips to UV-visible spectrometers. The system adopts As a light guide element, optical fiber is used for light splitting through grating. The processed light beam is projected parallel to the surface of the sensor, and then converted into an electrical signal. The data is then uploaded to the host computer through A/D conversion, signal storage and transmission in the circuit part. In the design of spectral image display and analysis, in order to allow the sensor photosensitive element to obtain a parallel beam with uniform monochromaticity and high resolution, it is necessary to build an optical system with a reasonable structure and size.

At the end of the article, through design and experimental comparison, it is verified that the miniature UV-visible fiber spectrometer designed with this solution has good UV sensitivity, with a spectrum range of 200nm to 400nm and a resolution of up to 2.0nm.

Application principle

During detection, connect the fiber spectrometer to the computer (USB interface) and power on, open the corresponding software of the instrument, and turn on the light source of the deuterium-halogen lamp. The composite light emitted by the deuterium-halogen lamp passes through the optical fiber and reaches the open area with an optical path of 10mm through the optical fiber probe. In the flow cell, the partially absorbed light is reflected by the coating mirror and then reaches the slit and planar grating monochromator through the optical fiber. The CMOS sensor converts the optical signal into the corresponding electrical signal. After being processed by the core data chip, the electrical signal is The signal is converted into a digital signal for display on the computer. The spectrometer selected for this instrument has a wavelength range of 200-400nm, a wavelength accuracy of ±0.3nm, and a wavelength repeatability of ±0.1nm (wavelength temperature drift 0.4nm/10°C).

Samples and test methods

There are five types of test samples in this test:

Calcium chloride, potassium chloride, sodium bromide, sodium iodide, sodium chloride solution (100ppm, 200ppm, 500ppm, 800ppm, 1200ppm, 2000ppm, 3000ppm, 5000ppm, 8000ppm, 10000ppm)

The UV-visible microfiber spectrometer ATP2002 produced by Aopu Tiancheng (Xiamen) Optoelectronics Co., Ltd. was used.

Test conditions: integration time 7 ms, average times 5 times, scanning range 180-420nm, room temperature.

Test results and analysis

4.1 Comparison chart of absorbance of calcium chloride solution 100-10000ppm

4.2 Comparison chart of absorbance of potassium chloride solution 100-10000ppm

4.3 Comparison chart of absorbance of sodium bromide solution 100-10000ppm

4.4 Comparison chart of absorbance of sodium iodide solution 100-10000ppm

4.5 Comparison chart of absorbance of sodium chloride solution 100-10000ppm

4.6 Lateral comparison data of light absorption of five samples

4.6.1 100ppm absorbance comparison chart

4.6.2 1200ppm absorbance comparison chart

4.6.3 2000ppm absorbance comparison chart

4.6.4 10000ppm absorbance comparison chart

Conclusion

This article introduces the basic principles of spectrophotometry. Through relevant experiments, it is verified that the spectrometer has good measurement accuracy and good stability, and provides a large amount of original data for using fiber spectrometer to test the absorbance of solutions. This spectrometer can be widely used to detect the absorbance of solutions.