SLOPE INDICATOR - 3-D JOINTMETER

Jointmeters are used to monitor movement at joints and cracks. Submersible sensors for 3-D jointmeters are designed to withstand extended underwater operation. Typical applications include:

• Monitoring movement at submerged construction joints in concrete dams.

• Monitoring joints or cracks in tunnels and tanks.

A 3-D jointmeter consists of three submersible displacement sensors and a mounting system. The exact design of the mounting system, which consists of a reference bracket and and three end brackets, depends on site specific details, such as the height of the joint covers and the degree of protection required. The drawing above illustrates the concept. In practice, the brackets are often designed by engineers at the site.

Two types of sensors are available: VW sensors, which are suitable for pressures up to 17 bar and and potentiometers, which are suitable for pressures up to 24 bar. The sensors are mounted parallel to the axis of expected movement. A change in the distance across the joint causes a change in the signal output by the sensor.

The initial reading is used as a datum. Subsequent readings are compared to the datum to calculate the magnitude, rate, and acceleration of movement at the joint.

Submersible: Two types of sensors are available.

• The vibrating wire sensor is rated for 17 bar (250 psi) of water pressure.

• The potentiometer-based sensor is rated for 24 bar
  (348 psi) of water.

Easy Installation: Installation requires only small diameter, shallow drill holes in the concrete slab.

Manual or Automatic Readings: The jointmeter is easily connected to a data logger for unattended monitoring.

Potentiometer-Based Submersible Sensor