Appliance Design - February 2008 - (Page 34) CONTROLS & SENSORS source. Polarization can also be used to distinguish characteristics of the solution [4]. In this case, Mie theory is further applied to include the polarizability of the surfactant in the solution. When the detergent is added to the water in the wash cycle, Micelles are formed due to the polar environment of the water. When probed with polarized light, the scattered light will tend to maintain its initial state of polarization. However, when the surfactant has acted on the debris, the result is an emulsion that contains much larger particles and results in light scattering that is not preferentially polarized. Using this knowledge, the turbidity sensor in Fig. 1 can be further enhanced to include a polarization analysis by placing a polarizer at 90 degrees to the incident laser light. When the fluid contains only detergent, there will be minimal scattering that changes polarization, but as the wash progresses, more light will enter the polarized detector. Turbidity sensing can also be beneficial in applications beyond washing. Similar Attribute Symbol Units SM VCSEL 5 1 20 760-860 0.01 0.06 0.25 <15 MM VCSEL 20 5 10 EE Laser 60 10 5 LED Electrical Power Optical Power Efficiency at POPT=1mW Wavelength Spectral Width Spectral Tuning (Temperature) Spectral Tuning (Current) Beam Angle (full width at half of maximum value) PELEC POPT η λ ∆λ ∆λ /∆Τ ∆λ /∆Ι ∠ mW mW % nm nm nm/°C nm/mA ° 60 1 2* 670-870 630-1300 400-1300 0.5 0.06 0.09 ~15 15 par 35 perp 120 2 0.3 50 0.3 Table 1. Comparison of the electro-optic properties of VCSELs, EELs, and LEDs. *Efficiency is defined with the optical energy emitted a 30 degree cone. concepts can be utilized in water purification systems in both the consumer and industrial environments. The ability to measure very low turbidity levels (0 to 10 Nephelometric Turbidity Units or NTUs) is beneficial to drinking water purification systems, and the ability to determine the LOW COST Variable Speed Controls For Fans, Blowers, Humidiers, Stoves, Heaters, Whole House Ventilators, Range Hoods, Lamps. . . DIAL-A-TEMP Plug-In 3.0 Amps-120VAC. KBWC-Wall Box Mount M 2.5, 5.0, 6.0, 8.0, 1 10.0, 12.0 & 15.0 Amp models, 120 & 240VAC, 50/60Hz. KB KBMC-Panel Mount 2.5 2.5, 3.0 & 4.0 Amp mo models, 120 & 240VAC, 50 50/60Hz. Designed for Shaded Pole, AC/DC and Permanent Split Capacitor (PSC) Motors. Send for complete literature. If it’s not in our catalog, let KB engineers design a custom control for your application. KB Electronics, Inc. 12095 N.W. 39th Street • Coral Springs, FL 33065-2516 954 346-4900 • Fax: 954 346-3377 • Outside FL 800 221-6570 www.kbelectronics.com • Email: info@kbelectronics.com particle size would be beneficial in determining water cleanliness in applications such as swimming pools and spas where the chemical agents used react in a similar manner as the surfactants in detergents. While the degree of complexity of the two methods above is certainly much higher than in traditional turbidity sensors, the amount of useful information obtained from the sensor will allow the machine to accurately control the amount of detergent, the amount of waste water, and ultimately the amount of energy used, all of which are becoming precious commodities, as well as differentiators in appliance design. The ability to measure the speed of particular objects in a consumer appliance is also of interest. Self-mixing is a technology that can be deployed to measure velocity of a mechanical part, fluid, or aerosol without any physical contact. The technology is based on a small amount of reflection from the object in motion being scattered back into the laser cavity, which modifies the lasing characteristics. This interruption causes measurable changes in the average optical power, and has a frequency component that is directly related to the speed of the moving object [5]. This approach can also be used to measure the vibration of a target object. Applications to the appliance industry include water flow measurements, motor speed, drum speed, motor and drum vibration, compressor vibration, all of which could be used to predict failure and warn the consumer. Self- For more Information Enter 114 34 applianceDESIGN AD11074KB.indd 1 February 2008 10/8/07 10:39:41 AM www.applianceDESIGN.com http://www.kbelectronics.com http://www.kbelectronics.com http://www.appliancedesign.com
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