Turbidity is the optical property that causes light to be scattered and absorbed, rather than transmitted. The scattering of the light that passes through a liquid is primarily caused by the suspended solids. The higher the turbidity, the greater the amount of scattered light. Since molecules in a very pure liquid scatter light to a certain degree, no solution will have zero turbidity. The USEPA Method 180.1 specify the key parameters for the optical system to measure turbidity for drinking, saline and surface water, in a 0 to 40 NTU range, using the nephelometric method.
HI 83414 and HI 88703 are designed to meet or exceed the criteria specified by the USEPA Method 180.1 and Standard Method 2130 B. The light beam that passes through the sample is scattered in all directions. The intensity and pattern of the scattered light is affected by many variables, such as wavelength of the incident light, particle size and shape, refractive index and color. The optical system includes a tungsten filament lamp, a scattered light detector (90°) and a transmitted light detector (180°).
In the ratio turbidimeter range, the microprocessor of the instrument calculates the NTU value from the signals that reach the two detectors by using an effective algorithm. This algorithm corrects and compensates for interferences of color, making the HI 83414 and HI 88703 color-compensated. The optical system and measuring technique also compensate for the lamp intensity fluctuations— minimizing the need of frequent calibration.
In the non ratio turbidimeter range, the NTU value is calculated from the signal on the scattered light detector (90°). This method offers a high linearity on the low range but is more sensitive to lamp intensity fluctuations.
The lower detection limit of a turbidimeter is determined by stray light. Stray light is the light detected by the sensors that is not caused by light scattering from suspended particles. The optical system of HI 83414 and HI 88703 is designed to have very low stray light, providing accurate results for low turbidity samples.
Range—Non Ratio Mode
|0.00 to 9.99; 10.0 to 40.0 NTU;
0.0 to 99.9; 100 to 268 Nephelos
0.00 to 9.80 EBC
Resolution—Non Ratio Mode
|0.01; 0.1 NTU
0.1; 1 Nephelos
|Range—Ratio Mode||0.00 to 9.99; 10.0 to 99.9; 100 to 4000 NTU
0.0 to 99.9; 100 to 26800 Nephelos
0.00 to 9.99; 10.0 to 99.9; 100 to 980 EBC
|Resolution—Ratio Mode||0.01; 0.1; 1 NTU
0.1; 1 Nephelos
0.01; 0.1, 1 EBC
|Accuracy||±2% of reading plus 0.02 NTU (0.15 Nephelos; 0.01 EBC)
±5% of reading above 1000 NTU (6700 Nephelos; 245 EBC)
|Repeatability||±1% of reading or 0.02 NTU (0.15 Nephelos; 0.01 EBC) whichever is greater|
|Stray Light||< 0.02 NTU (0.15 Nephelos; 0.01 EBC)|
|Light Detector||Silicon Photocell|
|Method||Nephelometric method (90°) or Ratio Nephelometric Method (90° & 180°), Adaptation of the USEPA Method 108.1 and Standard Method 2130 B.|
|Measuring Mode||Normal, Average, Continuous|
|Turbidity Standard||s <0.1, 15, 100, 750 and 2000 NTU|
|Calibration||Two, three, four or five-point calibration|
|Light Source/ Life||Tungsten filament lamp / Greater than 100,000 readings|
|Display||40 x 70 mm graphic LCD (64 x 28 pixels) with backlight|
|LOG Memory||200 records|
|Auto Shut-off||After 15 minutes of non-use|
|Environment||0°C (32°F) to 50°C (122°F); max 95% RH non-condensing|
|Power Supply||230 V/50 Hz or 115 V/60 Hz 20 W|
|Dimensions / Weight||230 x 200 x 145 mm (9 x 7.9 x 5.7”) L x W x H / 2.5 Kg (88 oz.)|