Principle of water quality monitoring instrument-Core parameters of optical filter|Maxoptics in China

Optical filter for water quality monitoring

Principle of water quality monitoring instrument and Core parameters of optical filter

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Optical Principles of Water Quality Monitoring Instrument
1. Spectrophotometry (COD, ammonia nitrogen, total phosphorus, heavy metals, etc.): Core principle: Based on the Lambert-Beer law, that is, the substance to be measured has characteristic absorption peaks at specific wavelengths, and the absorbance is proportional to the concentration.
2. Turbidity/Suspended Solids Detection (Scattering Method). Principle: Light illuminating suspended particles produces 90° scattering, and the intensity of the scattered light is positively correlated with turbidity (NTU).
3. Ultraviolet Absorption Method (UV254, Rapid Measurement of COD/TOC). It directly measures the transmittance of 254 nm ultraviolet light, corresponding to the concentration of organic matter, requiring no reagents and enabling rapid online testing.
Spectrophotometric Optical Path Structure of Water Quality Monitor
1. Single-beam vertical transmission type (portable / benchtop): light source (tungsten lamp/deuterium lamp/LED) → collimating lens (parallel light) → filter wheel/fixed filter (wavelength selection) → cuvette/detection cell (water sample) → condenser lens → photoelectric detector (silicon photodiode/PD/CCD) → signal amplification → absorbance/concentration calculation.
2. Dual optical path: includes a measurement/reference optical path. One path measures the sample, while the other measures the blank as a reference, allowing real-time correction of light source drift, temperature, and stray light interference.
Selection of Optical Filters for Water Quality Monitoring Instruments and Core Technical Parameters
1. Central wavelength: 420 nm, 470 nm, 520 nm, 540 nm, 620 nm, 690 nm. Ultraviolet: 254 nm (COD/UV).
2. Full Width at Half Maximum (FWHM): 8 nm ~ 12 nm Function: Ensure monochromaticity, avoid stray light interference with absorbance
3. Peak Transmittance Tmax (Visible Spectrum): ≥50%
4. Blocking: OD4 ~ OD6, light outside the passband is suppressed by 10⁴~10⁶ times.
Sizes can be customized, including φ10mm, φ12mm, φ12.7mm, φ15mm, etc.