Rod type extensometer for measuring distance change of two horizontal points of reservoir dam

The invention provides a rod type extensometer for measuring the distance change of two horizontal points of a reservoir dam, and the extensometer comprises a measurement end, a fixed end, a suspension spring suspension device, a base line, a calibration device, a sensor, and an electrical unit, one end of the base line is connected to the fixed end, the other end is connected with a measurement end iron core of the sensor, and the sensor is fixed at the measurement end. The measurement end is a micro-displacement platform and is composed of an upper-layer platform and a lower-layer platform,the lower-layer platform is fixed to a dam body, and the calibration device is connected with the upper-layer platform and can drive the upper-layer platform to move in the horizontal direction relative to the lower-layer platform; the electrical unit comprises a single-chip microcomputer, a lightning protection anti-interference circuit, a power supply module, a signal conditioning circuit, an optical coupler isolation c