Long-term, real-time and multi-channel distributed temperature monitoring system for tunnels in cold regions

Tunnel frost damage is common in cold regions and is of increasing concern. Temperature monitoring is crucial to reveal the tunnel temperature change laws and distribution characteristics and to complete a reasonable frost prevention design. In this study, a distributed temperature monitoring system for tunnels in cold regions is designed by using A level platinum resistance temperature sensors (PT100 A) and a series of electronic integrated chips to complete a long-term, real-time and multi-channel automatic temperature test in different positions in the tunnel. The constant current source method is adopted to test the platinum resistance of PT100 A, and a high-precision resistor is inserted in the circuit to improve the test accuracy. The resistance test error can be approximately 0.011, that is equal to 0.03 °C. The test resistance results are linearly converted to temperature at a calculation interval of 1 °C due to the strong linear relationship between the platinum resistance and temperature. In addition, the sensor error is compensated for on the basis of the calibrated results of sensors at 0 °C. Therefore, the accuracy of the final temperature results can be enhanced. The monitoring system has been applied in the actual tunnel, which can provide accurate, adequate and comprehensive temperature data for the optimal design of the thermal insulation layer thickness and length.