This publication is the result of a benchmarking effort undertaken under the IAEA coordinated research project on improved instrumentation and control (I&C) maintenance techniques for research reactors. It lays the foundation for implementation of on-line monitoring (OLM) techniques and establishment of the validity of those for improved maintenance practices in research reactors. The process data, available in the plant computer from sensors of technological processes, can be used to verify the calibration of the sensors. The data is easily retrieved from the plant computer and analysed to identify the sensors that have drifted beyond their allowable limits. The drifted sensors are then calibrated and the remaining sensors are left 'as it is' until the next calibration cycle. The techniques and guidance embodied in this publication will serve the research reactor community in providing the technical foundation for implementation of OLM techniques. It is intended to be used by Member States to implement I&C maintenance and to improve performance of research reactors.