Description
The ISO standard for turbidity measurement uses infrared wavelength of light that is outside the visible spectrum. The primary benefit of the ISO method over the EPA method is the reduction of color interference. The EPA method uses a tungsten lamp that produces light that contains all of the visible wavelengths of light that we see as white. A solution that is colored will be adsorbed by a complementary wavelength of light which will affect the turbidity reading. Since the ISO method is outside the visible wavelength of light the color in the sample does not interfere with the measurement. The USEPA prefers the tungsten lamp since it provides for better accuracy at low ranges and drinking water should not be colored. The requirements of an optical turbidity meter for the measurement of diffuse radiation used in low range measurements (i.e. drinking water) expressed as formazin nephelometric units (FNU) according to ISO 7027 are:
Measurement of diffuse radiation for water with low turbidity (0 FNU to 40 FNU)
The wavelength of the incident radiation shall be 860 nm
The spectral bandwidth of the incident radiation shall be less than or equal to 60 nm
There shall be no divergence from parallelism of the incident radiation and any convergence shall not exceed 1.5
The measuring angle, theta, between the optical axis of the incident radiation and that of the diffused radiation shall be 90° ±2.5.
The aperture angle should be between 20 and 30 in the water sample.
The HI98713 meets and exceeds the meter criteria specied by ISO 7027.
Principle of Operation
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 of the HI98713 includes a LED, a scattered light detector (90 degree) and a transmitted light detector (180 degree). Which detectors are used are based on the measurement mode.
The lower detection limit of a turbidimeter is determined by stray light that is detected by the sensors but not caused by light scattering from suspended particles. The optical system of the HI98713 is designed to have very low stray light, providing highly accurate results for low turbidity samples.
Turbidity meter light path
Turbidity Standards
The HI98713-11 AMCO AEPA-1 standards ensure that measurements are traceable to a primary reference materials. These standards are used for calibration and performance verification of the turbidity meter.
Supplied with Certificate of Analysis
Lot number
Expiration date
Standard value @ 25 C
Reference meter NIST traceable
Provided storage containers
Light tight
Protects from accidental breakage
Reviews
There are no reviews yet.