In-situ calibration of in-service strain sensing system under passive excitation: methodology and impacts assessment

Abstract

Aiming at the calibration of in-service strain sensing systems for structural health monitoring (SHM), a technical framework is proposed. A calibration method adapting to complex in-situ conditions is presented which defines the calibration prototype composed of measured variable, excitation source, reference system and sensing system. By analysing the operating procedure of the prototype, two measurement models are deduced for instantaneous and intermediate error analysis respectively. To discover the effects of the ambient temperature on the calibration process, the experiments are conducted using a temperature test chamber, and then the qualitative analysis and quantitative estimation are performed. The results show that: (a) With the variation of temperature, the responses of both resistance strain gauges (RSS) and fiber optic strain sensors (FOS) change significantly; (b) The relative strain deviations between the sensing system (SS) and the reference sensing system (RS) within −10 °C–50 °C fluctuate in a narrow range, for example 0.015–0.023 for RSS and 0.382–0.404 for FOS in this study, respectively; (c) The range of the deviations between SS and RS that is affected by temperature can be estimated with the proposed method, for example, 4.61 μϵ for RSS and 18.2 μϵ for FOS, respectively, with a confidence level of 95%.