1.Introduction

The geokon Model 6150F MEMS Digital Addressable In-Place Inclinometer system enables long-term monitoring of deformations in structures such as dams, embankments, foundation walls, and similar applications. The basic principle of operation is the use of tilt sensors to make accurate measurement of inclination, over segments of a borehole, which is drilled into the structure being studied. The instrument is designed to be installed in standard grooved inclinometer casing, which is installed in the borehole. Constant monitoring by the instrument allows for very precise measurement of changes in the borehole profile. Each tilt sensor is individually serialized and calibrated. A calibration sheet for each sensor is provided, showing the relationship between sensor output and inclination.

Each tilt sensor is comprised of two addressable Micro-Electro-Mechanical Systems (MEMS) devices inside a sealed stainless steel housing. The devices measure the A and B axes of the borehole. Each sensor also contains a thermistor for reading temperatures.

The tilt sensors are connected to each other using four-wire bus cable. Each sensor has a length of this cable exiting both the top and bottom of the housing. A male connector is attached to the cable exiting the top of the sensor and a female connector is attached to the cable exiting the bottom of the sensor.

The uppermost sensor of the string connects to a customer-specified terminator for attaching to the chosen readout (PC, datalogger, SCADA system, etc.).

The inclinometer system uses stainless steel tubing to mechanically connect the sensors, as well as to fix them at the customer-designated intervals. The tilt sensor housing has a wheel assembly and universal joint on its upper end. This centralizes the sensors in the casing, allows unimpeded relative movement of the spacer tubing, and accommodates any spiraling of the casing. The entire string is normally supported from the top of the casing by a suspension bracket.

 

Figure 1: Model 6150F Installed