Patent Application
20150276594
This invention is in the field of turbidity measurements or other turbidity sensing devices. In particular, the present invention relates to providing a compact, reliable and economical apparatus for measuring the turbidity or haziness of fluids.
The measurement of turbidity is used for many applications, the most common being in water quality testing. Specific applications include drinking water, waste water remediation, effluent discharge (e.g., in paper mills, electroplating, quarries, mining operations, and chemical plants), runoff, ocean monitoring, washing of clothes, and filtration processes.
Turbidity is also measured in the beverage industry. Alcoholic drinks (e.g., beer and ales, wine and spirits) involve suspended solids in their processes. Hefeweizen is a style of beer that is hazy by design, due to suspended wheat proteins. Chill haze is an undesirable turbidity that occurs in aged beers that are cold, and is attributed to coagulated proteins, tannins and polyphenols. A filtration process may separate grape skins and particulates from the liquid fraction in wine production. Potato remnants and charcoaled oak are removed from vodka and bourbon, respectively. Fruit drinks may or may not remove suspended pulp from juices. Centrifuges, whirlpools, separators and filters are elements in the quality process for making beverages where turbidity is monitored.
Blood constituents like red blood cells, white blood cells, hemoglobin, lipid particles, bile pigments, bilirubin and biliverdin may be quantified by turbidity measurements. The materials may also interfere with plasma and serum tests and need to be removed, typically by centrifugation and/or filtration, so that a quality test may incorporate turbidity measurements.
In all of the applications, particulate or other matter is often suspended or dispersed in fluids. Such haziness or cloudiness, termed turbidity, is measured by quantitating the amount of scattered light by the particulates. A sensor is typically ninety degrees from the initial light path. The amount of light scattered depends on many factors including the initial intensity of light, the light path, the fluid, the particulate size, shape, concentration and liquid and/or particulate interactions with light, the light scattering path and lengths, and the accuracy of and interaction of light with the sensor.
Tungsten lamps are common light sources in turbidity meters due to their availability and low cost. However, tungsten lamps degrade in light intensity over time which affects turbidity measurements. Frequent calibration by increasing input voltage is necessary to obtain a consistent initial intensity of light. Additionally, a cooling system is often needed for tungsten lamps. Laser light sources are also used, but complex electronics and cooling systems are often needed.
Photodiodes are commonly used sensors that are capable of converting light into either current or voltage. The responsiveness and error of a photodiode is dependent on its material composition and wavelength of light. Smoke detectors, camera light meters, compact disc players, and infrared remote control systems (e.g., television, garage openers and air conditioners) also incorporate photodiodes. Such consumer devices lack a need for a high accuracy, as compared to medical or scientific instruments. Medical applications, e.g., computed axial tomography (CAT scan) or computed tomography (CT scan) where three-dimensional imaging is performed requires highly accurate detectors. Also, scientific instruments like spectrometers and pulse oximeters also have a need for improved accuracy.
Known mechanism exist of using an LED as the light source, but the light source may be limited in being only monochromatic or without an LVF/photo array sensor.
In both U.S. Pat. No. 7,907,282 issued to Coates on 15 Mar. 2011 and U.S. Pat. No. 7,459,713 issued to Coates on 2 Dec. 2008, each of which are herein incorporated by reference, there is discussed potential use of LEDs and an LVF/sensor to measure turbidity.
Previous known implementations discussed above each lack having all of the following properties: a uniform, stable and long-life light source that does not degrade in intensity over time; an accurate sensor that may measure light intensity at one or more wavelengths in the ultraviolet, visible, and infrared regions; and a compact, portable, easy to use instrument. Thus, a need exists for an improved turbidity meter that overcomes the aforementioned issues
The present invention relates to instrument and sensor methods and systems. The present invention also relates to instruments that measure the turbidity and quality of fluid having particulate content therein. The present invention additionally relates to linear variable filters combined with photodiode-based sensors and methods thereof. The present invention also relates to light emitting diode devices and methods thereof. The present invention relates to turbidity sensors that monitor or measure the status of a fluid and determine the presence or level of particulates in or materials having different optical properties of the fluid. The present invention also relates to techniques for measuring concentrations of particulate matter in fluids.
A turbidimeter for measuring the turbidity of a sample of fluid comprises a transparent sample cell containing the sample, a light source comprising one or more light emitting diodes that directs a beam of light through the sample cell, and a light detector comprising of a linear variable filter coupled with a photoelectric sensor. The incoming light beam is typically at a ninety degree angle to the light detector, allowing scattered light to be measured. The arrangement is a compact apparatus, with no moving parts.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:
The schematic in
In terms of the inventive method and apparatus, it should be noted that the position of the LED or LEDs creates a light path that may be detected at angles not considered transmissive (i.e., non-transmissive angles), meaning zero degrees, or reflective, meaning one-hundred eighty degrees, but rather at an angle between, but not including, zero and one-hundred and eighty degrees, preferrably as ninety degrees. The LEDs emit light covering single or multiple wavelengths and detection of light within a fluid under test includes identifying a detected wavelength at a different wavelength or wavelengths from that emitted by the LEDs, such as in fluorescent, luminescent or phosphorescent processes.
The schematic shows the light scattering and detection process. An emitted light wave impinges onto a material which differs from the suspending fluid. The difference may due to, but is not limited by, size (e.g., at the molecular level or larger) or to refractive index, or both. Upon impingement, the material absorbs and scatters light based on its composition, size, and shape. The scattered light at 90 degrees is then detected and quantitated at the detector, and the instrument yields intensity of light at given wavelengths. Typically, turbidity or nepholemetry uses a scattering angle at 90 degrees from the emitted or incident light path.
In reality, there is a quantity of the scattering material, as opposed to just one as shown in the figure, and multiple light interactions, such as secondary scattering, are occurring between different materials or particles. However, the schematic shows the components and their relative placement, and to illustrate a simplified light scattering process.
Reference will be made to examples of the present invention.
This example demonstrates the layout and composition of the turbidity meter. A spectrophotometer (i-Lab® Model S560 from Microspectral Analysis, LLC of Wilton, Me., USA) was used with a modified adapter, where said adapter has an LED light source that shines a beam of light through a sample such that the emitted light path is at an angle of 90 degrees from the detector. The adapter and cuvette holding cell were modified as described above in
Formazin turbidity standards were made in accordance with ASBC Methods of Analysis 26-Formazin, and used within 24 hours. A standard of 1000 NTU (nepholometric transmission units) was used to make calibration standards. A graph of the NTU standards is shown in
Three different types of beers from Allagash Brewing Co., Portland, Me., were tested for turbidity. The beers used were the Allagash White, the Allagash Dubbel, and the Allagash Tripel. The Allagash White and Dubbel are considered “hazy” beers. The measurements were made using a calibrated, i-LAB® turbidity meter and a Haach 2100N bench-top turbidity meter (Haach Co., Loveland, Colo.). Ten measurements were made for both the i-LAB turbidity meter and the Haach instrument. The average turbidity was reported for both instruments, as well as the range (high and low values) for the i-LAB turbidity meter.
The results explained in Example 3 are shown below in Table 1 which include the turbidity measurement results for three beers. Here, the turbidity measurement for each beer type correlates to the visual appearance; i.e., for the hazy beers the Transmission of scattered light at 580 nm was >0.110 and the turbidity >67, and the “non-hazy”, transparent beer had a Transmission readings of <0.05 with a turbidity of <16. Further, the turbidity range is narrow and typically varies only +/−2.5 NTUs. This example shows that the i-LAB® turbidity meter can be used for a realistic application (in this case to quantitate the haze in beer), and that the measurements are narrow in range, and that the turbidity determinants are accurate and similar to those of a commercial, bench-top turbidimeter.
The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.
