JM Series Vibrating Wire Jointmeter
The JM series is a vibrating-wire displacement transducer used to monitor movement at joints, cracks and construction joints in concrete, rock and soil. Three models cover surface crack monitoring, embedment across construction joints, and borehole extensometer use.
- Range
- 25, 50, 100, 150, 200, 250, 300 mm (200/250/300 mm not available for JM-E)
- Accuracy
- ± 0.25 % F.S. (± 0.1 % in option)
- Operating temperature
- −20 °C to +80 °C
Overview
In detail
How it works
A vibrating-wire sensor is attached to a spring tensioned between two anchors. Any variation in distance between the anchors changes the tension in the wire, which the sensor converts to a displacement reading. The sensor is protected by a sliding stainless steel housing.
Models
The JM-S Crackmeter attaches to the structure surface using groutable or bolt-on anchors, with ball joints at each end to compensate for anchor misalignment; it is also available in a 3-D configuration for measurement in three orthogonal directions, or with special clamps for geogrid installation.
The JM-E Embedment Jointmeter is embedded in concrete so its active length spans the construction joint being monitored. It consists of a socket and a sensor section, installed and connected during two successive concrete lifts.
The JM-T is used in borehole extensometers and has an integrated thermistor for temperature measurement.
Operating conditions
The JM operates from -20 °C to +80 °C with an accuracy of ±0.25% F.S. (±0.1% optional) and a minimum resolution of 0.02% F.S.
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Specifications
Technical specifications
- Range
- 25, 50, 100, 150, 200, 250, 300 mm (200/250/300 mm not available for JM-E)
- Accuracy
- ± 0.25 % F.S. (± 0.1 % in option)
- Operating temperature
- −20 °C to +80 °C
- Resolution
- 0.02 % F.S. (min.)
- Overrange
- 1.00 × range
- Thermistor
- 3 kΩ (JM-T)
- Cable
- IRC-41A, IRC-41AP, IRC-390 (JM-E only), IRC-21A (JM-T)
- Length (JM-S, mid-range)
- 289.5 to 1076 mm
- Length (JM-E, at rest)
- 383 to 772 mm
Related
Often specified alongside
ESS Earth
Resistance Wire Extensometer RWE
- Application
- Underground hard rock and coal mine displacement monitoring
- Monitoring points
- Pillars, stope walls, roof
- Accuracy
- better than ±10 microstrain
- Spatial resolution
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