The GEOSTRING inclinometer is a vertical string of closely spaced MEMS sensors, ideal for low cost real time continuous and unattended monitoring of lateral displacement of soil, rock and structures.
The GEOSTRING system consists of several sensor nodes in a vertical string installed in either 70mm (2.75-inch) diameter inclinometer casing, 85mm (3.3-inch) inclinometer casing, or 38mm (1.5-inch) diameter Schedule 40 PVC pipe.
The pipe or casing provides access for subsurface measurements. The joints between each sensor are robust, allowing the system to maintain a consistent orientation of all the nodes, regardless of whether it is installed in ABS inclinometer casing or PVC pipe.
The pipe or casing is typically installed in a vertical borehole that passes through a suspected zone of movement. The nodes are spaced at 2 ft. (imperial version) or 0.5m (metric version) intervals and provide a reading resolution similar to a traversing probe. The system spans the zone of movement that occurs, and the pipe/casing moves as well, changing the inclination of the nodes inside.
Inclination measurements from the nodes are processed to provide graphs of the casing profile and changes in the profile. Changes indicate displacement (movement).
The system requires casings, segments, a suspension kit, a bottom plug, and a jumper cable.
Nodes, cables, connectors, and gauge rods are exceptionally durable, making it practical to remove the systems at the end of the project and redeploy them on other projects.
The GEOSTRING system is connected to a SENSLOG data acquisition system, and readings are transmitted to processing software that can trigger alarms based on displacements or rate of change.
Several Campbell Scientific data loggers can be integrated into a Roctest Senslog for GEOSTRING systems. Two systems can be connected on a CR6 or a CR1000X. With an MD485 module per GEOSTRING system, the CR1000 can read up to five systems, the CR800 three systems, and the CR300 one system.
GEOSTRING systems have joints capable of bending to 90°, allowing for a compact shipping option. Five segments, each 10 feet long (imperial version) or 2.5m long (metric version), can be shipped in a carton measuring approximately 64 x 64 x 64 cm (26 x 26 x 26 in) and which weighs less than 22 kilograms (50 pounds). Because of its compact size, the system can be shipped via standard overnight service.
| Sensor type | MEMS (Micro Electro-Mechanical Systems) tilt sensors for inclination readings. Thermistor for temperature readings. |
| Calibrated Range | ±30 degrees from vertical over a temperature range of -10°C to +40°C. |
| Resolution with SENSLOG | 9 arc seconds or 0.04 mm/m using the CR1000 data logger. |
| Repeatability | ±82 arc seconds or ±0.4 mm/m. |
| Power requirements | Minimum supply voltage of 10 Vdc. Maximum supply voltage of 30 Vdc. |
| Digital RS485 signal requires Campbell Scientific data logger. | |
| Housing | Stainless steel, 32 mm diameter, waterproof to 2 MPa |
| Weight | 0.54 kg per 0.6m (1.2 lb per 2 feet) gauge length. |
| Waterproof | Waterproof to 2 MPa (300 psi). |
| Signal Cable | Jumper Cable for connecting the system to the datalogger. Connectors are rated to 70 MPa (10,000 psi). |
| Casing | 70 mm (2.75 in) diameter casing. 38 mm (1.5 in) Schedule 40 PVC Pipe. |
| Data Logger | Compatible with CR6, CR300, CR800, CR1000 & CR1000X Data Loggers. MD485 RS-485 Interface required for CR300, CR800 & CR1000 Data Loggers. |
