1. The structure principle of the whole machine
The central control center of the instrument microcomputer is the CPU, and there are program memory (ROM) and data memory (RAM) to control the micro-current amplifier, display, stepping motor and other components through the input and output interfaces. Its structural principle block diagram is shown in Fig. 1.
After inputting the test mode (T, A, C, F.Linear Curve) and measurement parameters from the keyboard, the CPU controls the test mode according to the program set by the ROM and the data stored in the RAM, and processes and processes the measurement signal provided by the instrument. Control, realize measurement and corresponding operation.
working principle:
After turning on the power, light the light source lamp, and at the same time, the instrument conducts a self-test state under the control of the CPU (finding the light source switching position, wavelength limit position, filter position and finding the 0-level light or the characteristic spectral line of the argon lamp) to realize the automatic positioning of the wavelength (546nm ), then cut off the dark current of the photocell under the memory of the optical path, and the optical path will automatically open after the work is completed. At this time, the compound light emitted by the light source lamp enters the monochromator, and is dispersed by the grating to emit a beam of monochromatic light from the exit slit, which is received by the photocell through the sample chamber and converted into an electrical signal. Through the amplification of the amplifier and the A/D conversion, it is sent to the CPU. The CPU adjusts the automatic control by the software according to the received signal and the instructions of adjusting 0%T and 100%T, so that the signal can maintain a stable output and display on the digital display screen. 0.000A, realizing the purpose of automatically adjusting 0%T and 100%T/0A. Set the test wavelength during measurement, the CPU drives the wavelength stepper motor to the test wavelength according to the received instructions, puts the reference (blank) sample in the reference tank, presses the 100% T key, and the CPU , automatically adjust 100%T/0A. Then, enter the corresponding test program according to the set test mode and the input measurement parameters. When the sample to be tested in the sample slot enters the optical path, the monochromatic light is absorbed by the sample to be tested and the transmitted monochromatic light is received by the photocell, which is converted into an electrical signal proportional to the intensity of the transmitted light of the sample to be tested, and compared with the reference ( Blank) sample at the same level, after amplifier amplification, A/D conversion and corresponding calculation, the display will display the transmittance, absorbance or concentration of the sample to be tested.
Figure -, block diagram of the whole machine structure principle
2. Optical system principle
The instrument adopts a grating CT type single-beam structure optical path. The principle of the optical system is shown in Figure 2. The continuous radiation emitted by the tungsten-halogen lamp or argon lamp is concentrated by the condenser and then projected to the incident slit of the monochromator. This slit is just between the condenser and the On the focal plane of the collimating mirror in the monochromator, the compound light entering the monochromator becomes parallel light through the plane reflector and collimating mirror and shoots to the grating of the dispersion element. The continuous monochromatic light arranged uniformly in a certain order is resonated, and then shoots to the spherical reflector. Since the exit slit of the instrument is set on the focal plane of the spherical reflector, the monochromatic spectrum dispersed from the grating is imaged on the exit slit after being concentrated by the spherical reflector, and the monochromatic spectrum with a specified bandwidth is selected by the exit slit. The colored light falls on the center of the measured sample in the sample chamber through the condenser lens, and the transmitted light is transmitted to the receiving surface of the photocell after being absorbed by the sample.
Figure 2. Schematic diagram of the optical system
