Laser Based Calibration Technique of Thin Film Gauges for Short Duration Transient Measurements

Abstract

Surface temperature history and determination of convective heating rate are the important activity in many research programs for devising an effective cooling system in internal combustion engines or for typical high speed aerodynamic reentry vehicles. Thin film sensors have high response time (∼ few microseconds) and are invariantly used for these applications due to their precision measurement. Moreover, they can be fabricated in-house and thus cost effective. Present investigations are focused on the fabrication of such sensors and establishment of an experimental setup for calibration. Thin film sensors are prepared in-house by platinum ink mounted on an insulated substrate (Pyrex). Experiments are carried out by applying step heat load on the thin film sensor using laser light of known wattage. Recorded transient temperature data are processed for estimation of laser wattage using numerical and analytical models. For the known heating load, temperature signal is also predicted using one-dimensional transient heat conduction solver using ansys. Encouraging agreement of these predictions has demonstrated the success of the designed calibration set up and cost-effective means of in-house fabrication of thin film sensors.