Joint Meter is commonly used for strain measurements in foundations, piles, bridges, dams, tunnel linings, etc. Joint meters can be used either for surface mount application, embedded application or for 3-D/ trai-axial/perimetric monitoring purpose.

The Joint Meter of PMT consists of a vibrating wire sensing element anchored at one end and connected to a spring loaded push rod at the other end. For triaxial/3D measurement, this device can be assembled with three sets of transducers installed across the crack in three mutually perpendicular directions. As the push rod is moved out from the transducer body, the spring is elongated causing an increase in the vibrating wire tension. This tension is directly proportional to the spring extension and therefore the joint opening or closing results in a change in its signal frequency which is transmitted through a cable to the readout unit.