Abstract
Abstract. In measurement science and engineering, the method of compensation plays a decisive role and is widely used in practical applications, in particular for sensors and measurement systems, where high accuracy is required. However, a general theoretical system description of this method with particular respect to figures of merit in sensor technology does not exist yet. Nevertheless, this is important for a real understanding of the system's structure and its properties and would facilitate prospective sensor design. Within this work, we provide a general system-based description and comparison of both the compensation and the deflection method. Based on a general sensor model and selected transfer functions, which cover most sensor types, important sensor properties like static deviations in sensitivity, long-term drift effects, response time, output signal characteristics as well as nonlinearities and hysteresis are studied in a systematic fashion for both measurement methods. In the case of a compensation method, the core sensor element is part of a controlled closed-loop system, leading to different system properties compared to an open-loop sensor operated in deflection method. The influence of linear standard controllers, which are widely used in industrial measurement and control systems, is studied with respect to the sensor properties. In the conclusions we will summarize which controller type is appropriate for the attainment of a specifically targeted sensor behavior.
Highlights
“The history of science is the history of measurement” (Cattell, 1893)
Theoretical considerations concerning the properties of such sensors with respect to particular requirements in sensor technology like high sensitivity, fast response time, robustness against long-term instabilities of the core sensor element do not exist to our knowledge
This paper aims at a theoretical description of the compensation method in sensor technology
Summary
“The history of science is the history of measurement” (Cattell, 1893). Even though claimed by a psychologist in the late 19th century, the validity of this statement in the fields of science and engineering is unchallenged. The properties of the feedback loop can be set and tuned systematically This is the reason why the compensation method is used in particular in technical applications with high-precision requirements or expanded operation fields, like precision balances (Krause, 2005), AFMs (in constant force mode) (Bhushan, 2005), broadband lambda probes (Bosch GmbH, 2010), hot-wire anemometers (in constant temperature operation) (Fingerson and Freymuth, 1996; Tavoularis, 2005), MEMS-based accelerometers (Che and Oh, 1996; Stuart-Watson and Tapson, 2004), continous non-invasive blood pressure monitoring (Fortina et al, 2006), or even in hydrogel-based sensors very recently (Schulz et al, 2011) The goal of this study is a general understanding of the system behavior of a closed-loop sensor and to draw specific conclusions for system design and properties toward realization of high sensitivity, suppression of static systematic deviations, fast response, independence of interfering and long-term drift effects like material drift/relaxation and aging. A general sensor model is introduced, and different transfer functions, which mainly cover the transfer characteristics of
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