STRAIN DETECTOR

PURPOSE:To measure strain with good accuracy without failure even if there is a fluctuation in pressure by providing a strain detecting sensor in proximity to a measuring part and communicating the gas in a sensor container with a cover gas so that both gases are maintained under the same pressure. CONSTITUTION:The sensor container 16 provided with the sensor 6 is connected to a contactor 3 for setting the gage length G.L. of an object 2 to be measured. A bypass pipe 22 is connected via a piping 21 to the container 16 to communicate the gaseous Ar in the container 16 with the cover gas 10 in an Na container 15. A vapor trap 23 and a mist filter 24 are further provided between the bypass 22 and the container 15. The gaseous pressure in the container 16 and the gaseous pressure in the container 15 are thus equalized and since the intrusion of Na vapor and mist into the container 16 is prevented, the strain measurement with good accuracy for a long period is made possible without failure of the sensor 6.