Strain sensor

A strain sensor which is installed in a mount hole formed in a measuring target to measure a compressive strain occurring in the measuring target, the strain sensor having a length with a base end side and a front end side opposed to each other in an axial direction thereof, comprising:

• a first housing which has a length with a base end side and a front end side opposed to each other, the base end side being closer to an opening of the mount hole, the front end side being closer to a bottom of the mount hole, the first housing having a head which is formed on the base end side and placed on an end surface of the measuring target;
• a second housing which has a length with a base end side and a front end side opposed to each other, the base end side being closer to the opening of the mount hole, the front end side being closer to the bottom of the mount hole, the second housing being located closer to the front end side of the strain sensor than the first housing is and joined to the first housing, the second housing being in engagement with a thread formed in the mount hole;
• and
• a pressure measuring mechanism which is nipped by the first housing and the second housing, the pressure measuring mechanism having a base end side closer to the base end side of the strain sensor and a front end side closer to the front end side of the strain sensor,
• wherein the first housing has a first end portion located on the front end side thereof, the first end portion having a first face facing a front end surface of the pressure measuring mechanism which is located on the front end side of the pressure measuring mechanism,
• wherein the second housing has a second end portion located on the base end side thereof, the second end portion having a second face facing a base end surface of the pressure measuring mechanism which is located on the base end side of the pressure measuring mechanism, and
• wherein the pressure measuring mechanism is nipped between the first face and the second face and works to measure a change in compressive stress exerted by the measuring target on the first housing and the second housing in the axial direction of the strain sensor.