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EETE JUN 2014

SENSORS & DATA ACQUISITION Saving costs with sensors: what secrets do fluid colors tell us? By Kevin Jensen Smaler, faster , inteligent. When looking at the development process of Embedded Color Measurement Systems it is essential to know what the sideparameters are and what one wants to measure. Inline measurement or handheld solution? Color sensors enable multiple ways to uncover the secrets behind various fluid-, oil- or ink-based in various applications. The most important factor however remains: an intelligent measurement concept and system setup. The secret behind each measurement is to know how to achieve accurate values without drift effects. Color perception is based on three major variables: the Object, the observer and the light. White light is seemingly colorless, but in fact includes all colors of the visible spectrum. As soon as a white beam of light reaches an object only specific values of color is reflected and/or blocked. Only the color perceived will remain. Still, color can be perceived differently, when the main variables or conditions change. While unraveling the secrets of color, these aspects often are obstacles for a technological project. Therefore it is important to evaluate the overall measurement setup before deciding the general technological approach. Shifting the variables can be beneficial, if these are performed intentional. For example the statistical method of regression analysis allows various application-specific options. This evaluation methods allows to estimate the relationship between variables and draws conclusions based on color or spectral variations. Therefore it is possible to analyze an object or fluid that is outwardly clear or colorless via hyperspectral procedures. But what can one really detect with True Color XYZ with human eye perception) or Multi-Spectral Sensors (Spectral evaluation)? For example the German company MAZeT GmbH provides unique sensors with patented JENCOLOR interference filter technology. This special technology allows the sensors to measure at highest accuracy, without having color drift effects like common absorption filter based sensors. MAZeT’s JENCOLOR sensors are long-term stable, temperature resistant and cost-efficient. More than meets the eye Glucose, pH or chemicals are examples of the most common measurements in bio analytics, quality management, food processing or the medical industry. This article will demonstrate some sample applications, measurement values and accuracies. For example glucose measurements with color sensors can be performed via the pyranose oxidase method. A test setup based on transmittance and indirect determination utilizing ABTS as a redox indicator for the visual spectral range has been used to perform measurements. This method allows to measure the fraction of the incident light at a specified wavelength that passes through a sample. Colorless samples have been measured via fluorescence method. This method enables colorless chemical compounds to react with chemicals at certain wavelengths allowing various analysis options. The usage of ABTS as an indicator causes that the measured substances react to a green color range. The glucose test setup was further used to perform glucose measurements of soft drinks. Results ranging from 95+ mg/l for a Coke-like brand and Spritelike brand, 50+ mg/l for Ice Tea and nearly 40 mg/l for Fruko, a regional soft drink from Turkey – see figure 1. Even handheld transmission devices are possible. In this case it is common to perform zero-measurements of a sample and add an indicator to a fluid to allow accurate determination options of the sample composition. This kind of method is not solely useful for glucose or pH values, but allow allows various chemical compositions such as: Chlorine, copper, nitrite, phosphate and many others. Accuracy values for absorption measurements Fig. 1: Soft drink glucose measurements with color sensor. Fig. 2: Quasi-spectrum of Rodamin 6G (Absorption- and emission-based). Fig. 3: Illustration of common petroleum based color charts. with a pH indicator range from an error array of less than 0.1. If the results of absorption measurements are not accurate enough the results can be improved via the florescence method. Within the test setup it was possible to measure Roda- Kevin Jensen is Sales Engineer for North America, Canada & Europe at MAZeT – www.mazet.de – He can be reached at kevin.jensen@mazet.de 40 Electronic Engineering Times Europe June 2014 www.electronics-eetimes.com


EETE JUN 2014
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