The ESM-40S high sensitivity liquid level settlement system is designed for remote measurement of minute differential settlement in tunnels, bridges and buildings, etc. with high precision.
 
It consists of a low pressure, high sensitivity settlement sensors with digital output, connected in series to a reference reservoir and desiccant unit via fluid filled and air vent tubes respectively.
 
All interconnected settlement sensors are mounted at same elevation. They are connected in series by a fluid filled tube to a reference sensor mounted on stable ground, at same elevation. The settlement sensors and the reference sensor have a common fluid level initially. The fluid level in the reference reservoir is maintained almost constant. Settlement or heave of any sensor installed at settlement locations, causes difference in elevation between the sensor and reference reservoir, resulting in change in liquid head, which is read by the settlement transducer.