EL Beams Applications EL beam  sensors are used to monitor differential movement and rotation in structures.  Typical applications include: Monitoring stabilization measures, such as pressure grouting and  underpinning. Monitoring structures which may be affected by nearby tunneling and  excavating. Evaluating the performance of bridges and beams under load. Monitoring the stability of structures in landslide areas. Monitoring the deflection and deformation of retaining walls. Monitoring convergence and other movements in tunnels. Operation The beam sensor consists of an electrolytic tilt sensor attached to a rigid  metal beam. The tilt sensor is a precision bubble-level that is sensed  electrically as a resistance bridge. The bridge circuit outputs a voltage  proportional to the tilt of the sensor. The beam, which is typically one to  three meters long, is mounted on anchor bolts that are set into the structure.  The tilt sensor is then zero-adjusted and locked in position. Movement of the structure changes the tilt of the beam. Displacement,  the distance the structure has moved, found by comparing the current tilt  reading to the initial tilt reading and converting the angle to a linear  distance (See "principle" in drawing). Advantages High Resolution: The EL beam sensor can detect  a change in tilt as small as one second of arc, equivalent to a movement of  0.005 mm per meter of beam. Reliable Measurements: Since the EL beam  sensor has a defined gauge length, changes in tilt can be converted simply and  accurately to millimeters of movement, regardless of the rigidity of the  structure. Linked end to end, beam sensors can provide absolute displacement and  settlement profiles. Convenient to Install: A low profile design  makes the EL beam sensor practical to install in tunnels and other locations  where clearance is important. The length of the beam can be modified to fit the  structure, and special mounting brackets provide easy installation on curved or  distorted surfaces. Simple and Robust: The electrolytic tilt  sensor has no moving parts, and its insulated packaging provides thermal  symmetry, shielding it from the effects of temperature gradients and radiated  heat. Remote Readout: In construction-control  applications, beam sensors are connected to a data acquisition system that  continuously monitors movements and triggers alarms when threatening movements  are detected. In less critical applications, beam sensors can be read manually  at a remote terminal box with a hand held readout. Cost Effective: The EL beam sensor provides  reliable, high-resolution measurements, is simple to install, and is easily  connected to a data acquisition system. It represents an efficient and  economical alternative to precision leveling surveys and settlement profiling  systems.