Magnet Extensometer is designed to monitor settlement or heave of retaining wall, foundation, dam, soft ground. 
This system is composed of Probe, Reel Frame, signal tape, light, buzzer and several Spider magnet, guide pipe. 
Several Magnets which are installed in guide pipe have settlement or heave according to up-and-down motion of strata. 
If moving Probe with guide pipe then entering into magnetic field from Magnet, read switch is closed then light and 
buzzer will operate. 
At this time, it is possible to measure the depth of Magnet. Particularly, signal tape is treated with coating at steel tapeline 
so secured durability.