This paper presents a comprehensive review of bending sensors and their classifications. The main focus is on advancements in the design of optical fibre bending sensors based on fibre Bragg gratings (FBGs). Various measurement principles employed in optical fibre bending sensors are analysed, highlighting their respective advantages and limitations. Particular attention is given to sensors utilising long period gratings (LPGs), Tilted fibre Bragg gratings (TFBGs), and multicore (MCF) fibre structures, which demonstrate significant potential for the development of highly sensitive and compact bending sensing systems. 

The article describes digital and analogue methods for linearising the conversion function of thermoresistive transducers, with a detailed analysis of analogue methods. Analogue methods for linearising bridge circuits and measurement circuits based on passing a reference current through a resistance temperature detector (RTD) are considered. Linearisation of bridge circuits is based on the formation of the compensatingsupply voltage of the bridge circuit, which depends on the change in the measured temperature. When using the measurement method based on passing a reference current through an RTD, nonlinearity compensation is achieved by changing the conversion coefficient of the measuring signal or passing an additional current through the RTD, which linearly depends on the value of the RTD’s voltage change (measured temperature value). When passing an additional compensation current through the RTD, the nonlinearity error is not grater than0.1°C in the range of 0...800°C, and the schematic diagram of the measuring transducer contains a minimum number of elements, which allows to increase its reliability. In general, the choice of a linearisation method depends on the requirements for accuracy, operation rateand resource limitations of the measuring system.

This publication investigates the influence of external factors on the readings of heat flow sensors located at different distances from the heat source. ARIMA models with Gaussian distributions and t-distribution were used for the analysis, as well as Quantile-Quantile plots to assess the appropriateness of the distribution of model residuals. It was found that the influence of external factors varies significantly depending on the distance of the sensor to the heat source, which is confirmed by the results of the analysis. Sensors located closer to the heat source showed greater sensitivity to environmental changes, while sensors at a greater distance showed more stable readings. The obtained results emphasize the importance of taking into account external factors during the placement and operation of heat flow sensors to ensure maximum measurement accuracy.

The article presents a method of implementing a functionally integrated device for temperature measurement, which allows for controlled heating of the primary temperature transducer, measurement of the heating temperature as well as the temperature and differential temperature of the investigated and reference samples. The heating speed is regulated by the selection of the frequency and duration of the control impulses. To measure the temperature and temperature difference, it is proposed to use measuring currents of different polarity, which make it possible to simplify the device design. The methods of linearisation of the conversion function of primary temperature transducer based on the formation of compensating currents in given measurement ranges have been investigated. The conducted studies showed that the temperature measurement error does not exceed 0.11°C and 0.005°C in the control heating mode and in the temperature measurement mode, respectively. The temperature measurement error of the investigated and reference samples and the differential temperature measurement error does not exceed ±0.003°C and 0.001°C, respectively.