●Scattering photoelectric turbidity meterAppearance and structure
1. Light source 2, digital display window 3, sample room
4. Pull rod 5, zero adjustment button 6, calibration button
7. Range selection button 8 power switch
Main indicators and technical parameters
Measurement range 0-1.000 1-1.00 10-100NTU
Zui small resolution 0.001 NTU
Accuracy ± 5% F · S
Working environment temperature 0-35 ℃
Power supply voltage 220 ± 20V, 50HZ
Dimensions 450 × 350 × 120
Weight 15kg
●Scattering photoelectric turbidity meterWorking principle and characteristics
1Adopting the principle of integral sphere turbidity measurement：
A beam of parallel light propagates in a transparent liquid, and if there are no suspended particles in the liquid, the direction of the beam will not change when propagating in a straight line; If there are suspended particles, the beam will change direction when encountering particles (regardless of whether the particles are transparent or not). This forms what is called scattered light. The more particles (higher turbidity) there are, the more severe the scattering of light becomes.
As shown in the figure: the incandescent light emitted by the lamp source is converged by a condenser lens and shines on the pinhole; The collimating objective converts the light emitted from the pinhole into a highly parallel beam of light that exits; Parallel light is decomposed into transmitted light and scattered light (denoted as Tp and Td respectively) after passing through the sample, and enters the integrating sphere. There are two photosensitive elements installed on the inner wall of the integrating sphere, which respectively receive transmitted light and scattered light. After the light signal is amplified and processed by the circuit, it is displayed according to the following formula:
Turbidity=K × scattered light flux/transmitted light flux
=K × Td/Tp
K: Proportional constant
2The measured value is not affected by the color of the liquid：
Assuming the sample is colorless, the incident light flux entering the liquid is lo, and the outgoing light flux is also 1o. The relationship between outgoing luminous flux, scattered luminous flux, and parallel transmitted luminous flux is (without considering the reflection, absorption, etc. of the colorimetric dish):
1o=Tp+Td
If the sample is colored, the incident light entering the liquid will be partially absorbed. Assuming the liquid transmittance is T, there is a relationship between the outgoing light flux 10 ', scattered light flux Td', and parallel transmitted light flux Tp '.
1o '=T × 1o Tp'=T × Tp Td '=T × Td
That is to say, the intensity of both transmitted and scattered light decreases by the same coefficient T.
At this point, the turbidity measurement value will remain unchanged:
Turbidity=K × scattered light flux/transmitted light flux
=K × Td '/Tp'=K × T × Td/T × Tp
=K × Td/Tp