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Inclination monitoring

 

The society keeps building more ambitious projects. With higher skyscrapers, longer bridges and larger dams, the use of monitoring becomes a necessity. The constructions are exposed to many dangers, including seismic activities, structural deformation and corrosive weather.

This application note develops two different cases:

  • Slope indicator probes in boreholes
  • Structural inclinometers fixed to critical spots

 

Explanation of the System

Slope Indicator Probe

Geophysical monitoring analyses the soil’s displacement in order to predict catastrophic landslides and similar disasters. Boreholes are drilled along the slope of a mountain, so that critical areas are identified. The probes with embedded inclinometers are disposed as shown below.

 

vertical slope inclinometer
Figure 1: A vertical slope inclinometer

 

Structural Inclinometer

A first possibility involves a sensor fastened to a building’s foundations in order to detect the effects of collapsing fields. Another solution is to install beams with embedded inclinometers vertically or horizontally to buildings.

 

The types of applications in urban survey
Figure 2: The types of applications in urban survey

 

 

 

Environmental Analysis

Slope Indicator Probe

The inclinometers located in boreholes are required to provide accurate readings during a long period of time. They also have to withstand very humid environments. One to two sensors per probes are sufficient to get sufficient data. The inclinometer wake up every hour to make a measurement.

 

Structural Inclinometer

The sensors need to be extremely accurate as the weight of the building is massive: even a microscopic variation of angle may affect the entire structure. Depending on the situation, the temperature variation has to be often considered.

 

 

Performance Required

Slope Indicator Probe and Structural Inclinometer

  • Very low resolution < ±0.002°
  • Accuracy < 0.05° after compensation
  • ΔT = 5°C for slope indication
  • ΔT = 40°C for structural inclinometer

 

The arch dam at Emosson needs precise monitoring
Figure 3: The arch dam at Emosson needs precise monitoring

 

 

The MEMS Potential

Slope Indicator Probe

Servo-accelerometers measure inclination with high precision, despite their power consumption, large dimensions and expensive price. Today, the small size and improvements in the performance of MEMS accelerometers make them more suitable for this application. An important advantage is the autonomy of these sensors, as they need very low current to operate.

 

Structural Inclinometer

The MEMS capacitive sensors offer a simple, yet efficient solution for long-term structural monitoring. Nowadays, their technology, portability and accuracy satisfy the requirements for civil surveys.

 

 

Glossary

 

  • DC:                   Direct current
  • FS:                    Full scale
  • GPS:                 Global positioning system
  • Hz:                    Hertz
  • MTBF:              Mean time before failure
  • MEMS:             Microelectromechanical systems

Recommended Sensor

Colibrys MS9001 inclinometer is a high performance capacitive MEMS for inclination monitoring.

TS9001 Inclinometer

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