JM Series Vibrating Wire Jointmeter

The JM series of vibrating wire (vw) displacement transducers are used to measures movements at joints and cracks and foundations (concrete, rock and soil).


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.

Range 25, 50, 100, 150, 2001, 2501, 300mm
Overrange 1.00 × range
Accuracy ± 0.25 % F.S. (± 0.1 % in option)
Resolution 0.02 % F.S. (min.)
Operating temperature −20 °C to +80 °C
Thermistor 3 kΩ
Cable IRC-41A, IRC-41AP, IRC-3902, IRC-21A (JM-T)
Length ‘A’ of JM-S (mid-range) 289.5, 357, 500, 651, 797, 933, 1076 mm
Length ‘A’ of JM-T (mid-range) 230.5, 298, 442, 593, 738, 875, 1018 mm
Length of JM-E (at rest) 383, 432, 602, 772 mm
Diametre of JM-E (flanges) 47.6 mm
 Ranges not available for JM-E model
2 Available only with JM-E