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Turbidimeter used in laboratory

1. What is turbidimeter?
    1.1 Working principle of turbidimeter
    1.2 Structure of turbidimeter
    1.3 Feature of turbidimeter
2. Nephelometric turbidimeter
3. Use of turbidimeter
    3.1 Precaution of turbidimeter
4. How to buy turbidimeter?

What is turbidimeter?

Turbidimeter is a special instrument for determining the turbidity of water based on the principle of scattering or transmission of light by turbid liquid and is generally used for continuous automatic determination of turbidity of water.

Turbidity is the degree of cloudiness of water. It is caused by the presence of trace amounts of insoluble suspended substances, colloidal substances in water, and the measurement unit used in the ISO standard is FTU, which is consistent with NTU. A turbidity meter is based on this principle to measure the turbidity of water.

Working principle of turbidimeter

Turbidimeter is a device to measure the turbidity of water. There are scattered light types, transmitted light types, and transmitted scattered light types, collectively known as optical turbidimeters. The principle is that when light is shone on the surface of a liquid, there is a correlation between the ratio of incident light intensity, transmitted light intensity, scattered light intensity, and the turbidity of the water sample. The turbidity of the water sample is then determined by measuring the ratio of transmitted light intensity, scattered light intensity to incident light intensity, or transmitted light intensity to scattered light intensity. Optical turbidimeter is used in the laboratory, but also the field for automatic continuous measurement.

A. Integrating sphere turbidity measurement principle

A parallel beam of light propagates in a transparent liquid, if there are no suspended particles in the liquid, then the beam will not change direction when it travels in a straight line; if there are suspended particles, the beam will change direction when it meets the particles (regardless of whether the particles are transparent or not). This forms the so-called scattered light. The more particles there are (the higher the turbidity) the more severe the scattering of light will be. Turbidity can be measured by an instrument called a turbidimeter. The turbidimeter emits light that passes through a section of the sample and detects how much light is scattered by the particles in the water from a direction that is 90° to the incident light. This method of scattered light measurement is called the scattering method. Any true turbidity must be measured in this manner. Turbidimeters are suitable for both field and in-lab measurements as well as for continuous monitoring around the clock. A turbidity meter can be set up so that it will sound an alarm if the measured turbidity value exceeds a safety standard.

The incandescent light from the lamp source is converged by the focusing mirror and then shines on the pinhole; the collimating objective turns the light from the pinhole into a parallel light with good parallelism; the parallel light is decomposed into transmitted light and scattered light (respectively recorded as Tp) and Td) after the sample and enters the integrating sphere. The inner wall of the integrating sphere is equipped with dipolar photosensitive elements, which receive transmitted light and scattered light respectively. The transmitted light signal and the scattered light signal are amplified and processed by the circuit and displayed according to the following equation.

Turbidity = K x scattered light flux/transmitted light flux = K x Td/Tp

K: proportionality constant.

B. Measured values are not affected by the color of the liquid

Assuming that the sample is colorless, the incident luminous flux into the liquid is l0, and the incident luminous flux is also l0. The relationship between the incident luminous flux, scattered luminous flux and the luminous flux in the parallel transmission is as follows (without considering the reflection and absorption of the colorimetric vessel): l0=Tp+Td

If the sample is colored, the incident light entering the liquid will be partially absorbed, let the liquid transmittance be T. At this time, the outgoing light flux l0, scattered light flux Td, and parallel transmitted light flux Tp are related. l0,=T×l0Tp,=T×TpTd,=T×Td

Whether transmitted light or scattered light their intensity is attenuated by the same factor T. At this point, the turbidity measurement will remain the same:

Turbidity = K × scattered light flux / transmitted light flux



Structure of turbidimeter

a. Shell

b. Range indicator

c. Fuse holder

d. Power socket

e. AC/DC pull switch

f. Sample chamber cover

g. Digital display window

h. Zero-hand wheel

i. Range selection key

j. Power switch

Feature of turbidimeter

a. The water sample cup has anti-fog performance, so it can also be used for turbidity measurement of water samples in the rainy season.

b. Dual-use for AC and DC, easy to carry.

Nephelometric turbidimeter

Scattered light type, transmitted light type, and transmitted scattered light type are commonly known as optical turbidimeters, and online turbidity analyzers.

Online turbidity analyzer

Online turbidity analyzer, with a built-in microprocessor, advanced configuration, powerful, is a very sophisticated turbidity measurement instrument.

Based on the principle that the infrared light source of 860nm passes through the optical lens and penetrates the sample liquid, measuring the scattered light in a 90° direction according to ISO7027 standard, this turbidity analyzer can be used to measure the turbidity of raw or pure water in different places of filtration devices, such as drinking water, various production, and industrial water, as well as any place where qualified water is used. The product is compact, with a built-in backlit LCD screen, data memory, and relay control output (3 ways). The turbidity controller outputs a 4~20mA isolated signal to transmit reliable data wherever turbidity needs to be monitored and controlled.


a. With chromaticity compensation function, it makes the optical lens filter any scattered light to be compensated.

b. Special defoaming device of the sensor in effective prevention of bubble interference.

c. Relay contact outputs (3 ways): H, L, cleaning control.

d. Microprocessor-based digital program controller.

e. Large backlight LCD (192*64 dot matrix).

f. Independent 4~20mA DC variable transmission output.

g. Automatic scraping and cleaning control function.

h. Bracket mounting / 2B pipe strut mounting method.


a. Municipal water supply

b. Drinking water treatment plant

c. Sewage treatment plant

d. Integrated purification ponds

e. Pulp and paper industry

f. Wastewater treatment plant

g. Manure treatment plant

h. Chemical industry

i. Industrial wastewater treatment

j. Livestock wastewater treatment

Technical parameter

Measurement rangeFlow-through type 0∼100 NTU
Input type 0∼4000 NTU
Electricity supplyAC 220V 50/60Hz,±10% 3VA
DisplayImage data dot matrix LCD 192*64 pixels
Alarm contact capacity250V/2A (H, L)
Operating temperature range-25℃∼70℃
Environmental relative humidity0-90% (non-condensing)
PrecisionLess than ± 2 % FS
Reproducibility± 0.2 % FS
Response time300 seconds (90% range change)
Relay output4∼20mA, RS485
Temperature compensationAutomatic/Manual Temperature Compensation (Pt100/Pt1000)
Measurement principle860nm infrared light 90° scattering principle
Flow rate100 ml/min∼600 ml/min
Sensor calibrationManual calibration
Cleaning functionAir cleaning
Secondary meter housing materialABS
Secondary meter size155mm (W)×155mm(H)×110mm(D)
Secondary meter protection levelIP54, indoor
Secondary meter installation methodPipe-mounted, wall-mounted

Use of turbidimeter

a. Check the turbidity standard plate carefully, if there is dust and stain, use degreasing cotton with ethanol and ether half mixture to wipe clean, cuvette can be cleaned with detergent or detergent, then rinse with water, two light-transmitting surfaces wipe dry. Preheat the instrument for 10 minutes.

b. Range selection knob set to "100" file, insert the turbidity standard plate (with the numbered side facing left) immediately behind the sample tank.

c. Pull the lever to push in, so no object is placed in the optical path, adjust the "zero" knob to make the display read "0" (air calibration zero), pull out the lever, and the turbidity calibration accuracy plate is placed in the optical path, adjust the (calibration) knob to make the display read the factory calibration value of the turbidity standard plate -NTU, after this "calibration" knob cannot be changed at will, take out the standard plate.

d. Ranges "1" and "10" use a 30mm cuvette. Range "100" using 5mm cuvette. 5mm cuvette inserted immediately to the right.

e. Put turbidity-free water in the cuvette (about 3/4 height), put it in front of the sample tank, the measured liquid into the back of the sample tank (the size of the cuvette is close to the right side), push in the lever, adjuster section "zero" button so that the display number is 0. Pull out the lever, the sample is placed in the optical path, the display value is the measured liquid turbidity value NTU.

f. Measurement in the "range" selection key if you need to convert, in addition to the choice of the different cuvette, no turbidity water zeroing steps must be repeated once.

g. The standard plate of this instrument has been calibrated with a standard solution before leaving the factory, if the user needs to recalibrate, just use 10FTU standard solution and zero turbidity water to reverse the above steps and re-measure the calibration value.

Precaution of turbidimeter

a. The cuvette must be free of any dirty spots on both sides and bottom of the cuvette during the measurement.

b. If the old cuvette is used to hold the sample and "0" water during the measurement, it must be filled with "0" water at the same time before the sample is tested.

c. If the measurement sample is small, zero and sample measurement can use the same cuvette, so that both the organ-reported old cuvette Will not bring into the cylinder difference, which is conducive to the reliability of test data and avoid unnecessary operating errors.

How to buy turbidimeter?

ANTITECK provide lab equipment, lab consumable, manufacturing equipment in life sciences sector.
If you are interested in our turbidimeter or have any questions, please write an e-mail to, we will reply to you as soon as possible.

    AntiTeck Life Sciences Limited

    A1-519, XingGang GuoJi, Yingbin Road, Huadu, Guangzhou, China, 510810
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