The JM utilizes a vibrating wire sensor attached to a spring tensioned between two anchors. Any variation of distance between these anchors will change the tension in the wire. The sensor is protected by a sliding stainless steel housing.
3 models are available:
The JM-S Crackmeter is attached to the surface of the structure using groutable or bolt-on anchors. Ball joints at each end of the sensor compensate for any anchor misalignment. The JM-S is also available in 3-D configuration for measurement in three orthogonal directions, or with special clamps for installation on a geogrid.
The JM-E Embedment Jointmeter is embedded in concrete structures such that its active length spans the construction joint to be monitored. This model consists of two sections: the socket and the sensor, which are installed and connected during two successive concrete lifts.
The JM-T is used in Borehole Extensometers.
A thermistor is integrated to the JM allowing temperature measurement.