Introduction to Tilt Sensors
Applications
Tilt Sensors are used to monitor changes in the tilt of a structure. Such changes may be caused by excavation, tunneling, dewatering, or loading of the structure. Typical applications for tilt ssensors include:
- Monitoring stabilization measures, such as pressure grouting and underpinning.
- Monitoring structures for the effects of tunneling and excavating.
- Monitoring the deflection and deformation of retaining walls.
- Monitoring convergence and other movements in tunnels.
- Providing early warning of threatening deformations, allowing time for corrective action to be taken.
Types of Tilt Sensors
EL Tilt Sensor
EL tilt sensors are high resolution, narrow-angle tilt sensors ideally suited for monitoring structures.
Advantages: Accurate, high-resolution measurements, can be read remotely, easily automated, compact, reusable, reasonable cost.
Limitations: Some applications require temperature corrections, although careful placement of the tilt sensor can minimize this need.
EL Beam Sensor
EL beam sensors are similar to EL tiltmeters, except that the tilt sensor is mounted on a rigid beam with a defined gauge length, typically 1 to 2 meters long. Each end of the beam is anchored to the structure.
Advantages: The rigid beam makes it easy to convert changes in tilt to millimeters of movement (settlement, heave, convergence, or lateral displacement). Also, beam sensors can be linked end-to-end to monitor differential movements and provide absolute displacement and settlement profiles.
Limitations: Some applications require temperature corrections, although careful placement of the tilt sensor can minimize this need.
MEMS Tilt Sensor
The MEMS tiltmeter is medium-resolution tiltmeter that offers a wider measurement range of +/- 10 degrees.
Advantages: Waterproof, available in uniaxial or biaxial versions, can be read remotely, easily automated, compact and easy to install, reusable.
Limitations: Less sensitive than the EL tilt sensor.
Portable Tilt Sensor
The portable tiltmeter is carried from tilt plate to tilt plate to obtain measurements.
Advantages: A single tilt sensorcan be used to monitor any number of inexpensive tilt plates. The tilt sensor uses the same reliable servo-accelometer sensor that is used in the Digitilt inclinometer probe.
Limitations: No remote reading, cannot be automated, accuracy affected by placement of tilt sensor on tiltplate.
Track Monitor
Track monitoring sensors monitor settlement and twist in railway tracks. This is a specialized application for tilt sensors. Two versions are available: one based on the narrow-angle beam sensors and the other based on wider angle EL or MEMS sensors.
Advantages: Mounts directly on ties. Can survive reballasting operations. Can be read remotely, easily automated.
Limitations: Cannot provide readings during passage of train.
Deep-Water Tiltmeter
This special-purpose tilt sensor is based on the EL tilt sensor but housed in a thick, brass housing that is waterproof to 3 Mpa. Designed for use on CFRF dams.
Advantages: High resolution measurements, remote reading, easily automated, waterproof to 3Mpa.
Limitations: Signal cable must be protected by waterproof conduit.