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Crack Meter
Kingmach Crack Meter include the JMDL-31XXAT Smart Multipoint Displacement Meter for tunnels, rock slopes, foundation pits, and surrounding rock layers. This product is not used like a surface joint gauge. It is built for boreholes where movement must be separated by depth. The instrument group includes displacement gauges, PVC measuring rod protective tubes, anchor heads, and multipoint installation kits that support three to five points. During installation, the borehole is prepared, anchor heads are set at selected layers, and grouting fixes each anchor to its target rock or soil zone. Listed models include 50 mm, 100 mm, and 200 mm ranges, all with 0.01 mm resolution. The sensing circuit changes output frequency as the measuring rod moves through the coil, so each channel can report how one anchored layer moves relative to the reference head. This layout is useful when tunnel crown movement, slope slip, or foundation pit deformation may start at one depth before it appears elsewhere. Field records should emphasize borehole number, anchor depth, grout condition, channel order, and the direction of expected movement. During later review, engineers can compare shallow and deep anchors to judge whether the deformation is local relaxation, progressive sliding, or full-section movement. That layered view is the main reason to use a multipoint instrument instead of several unrelated surface gauges.
Application of Crack Meter
In integrated structural health monitoring, Crack Meter act as the movement layer inside a wider measurement network. Their role is to show where a point has shifted, how fast the shift is developing, and whether the change agrees with other instruments. Kingmach displacement products can feed digital records into acquisition units and monitoring platforms, while related Kingmach product groups provide strain, load, settlement, tilt, vibration, pore pressure, water level, rainfall, data logging, cables, and software. A practical system may use JMDL-52XXADT meters for precise joint travel, JMDL-31XXAT meters for rock layers, JMDL-24XXAT meters for buried geogrid deformation, and JMLS-22XXADT sensors for longer cable travel. The data chain should define point names, units, zero values, sampling intervals, warning grades, and inspection actions before alarms are enabled. This prevents a displacement curve from becoming an isolated chart. Instead, the reading can be checked beside force, strain, settlement, temperature, rainfall, and construction records, giving engineers a clearer basis for maintenance and warning review. During commissioning, each curve should be verified against the physical point so later reports can be trusted by site teams, designers, and owners. The same record should also note cabinet number, logger channel, cable tag, power supply, and communication route, because many long-term data problems begin outside the sensor body.
The future of Crack Meter
Longer service life will be a major future requirement for Crack Meter. Infrastructure owners want monitoring systems that remain useful beyond the construction phase and into operation, inspection, repair, and renewal. Kingmach lists 30-year designed service life on selected products such as the JMDL-24XXAT flexible displacement meter and JMDL-49XXAT formwork displacement meter, while models such as JMCW-21XXADT use non-contact sensing to avoid mechanical wear. Future specifications will likely ask more directly about waterproof rating, connector durability, cable route protection, sensor replacement access, and data continuity after maintenance. For dams, bridges, railways, slopes, and tunnels, a displacement record over several years is often more useful than a short burst of high-frequency data. This long view supports asset management and helps distinguish slow structural change from normal seasonal movement. The next improvement will be planned service records: expected inspection intervals, spare part notes, replacement dates, and clear links between old and new baselines after a sensor is changed.
Care & Maintenance of Crack Meter
For Crack Meter installed at cracks, joints, and expansion joints, maintenance should focus on bracket stability, rod alignment, cable protection, and baseline traceability. Kingmach JMDL-22XXAT crack gauges may use different measuring rods and universal bases, so the mounting points must remain firm while the structure moves naturally. Avoid placing rods where they can be hit by workers, tools, vehicles, concrete debris, or repair materials. During inspections, check whether the crack edge has spalled, whether the base has loosened, whether water has entered the connector, and whether the displayed movement agrees with nearby observations. Because the product can store up to 600 measurement results, compare field readings with stored records before resetting values. If temperature versions are used, keep temperature data with displacement data so seasonal opening and structural movement are not confused. Keep the installation photo, point number, zero value, and expected movement direction with the commissioning record for later review. If a reading changes after maintenance work, inspect the base, anchor, cable, and cabinet before assuming the structure itself has moved.
Kingmach Crack Meter
Crack Meter are used when a structure needs movement data that can be reviewed, compared, and acted on before deformation becomes visible. Kingmach covers short range crack movement, expansion joint travel, rock layer displacement, geogrid deformation, draw-wire movement, and long stroke position tracking. The category includes JMDL-21XXAT general-purpose displacement meters, JMDL-22XXAT crack gauges, JMDL-24XXAT flexible meters, JMDL-31XXAT multipoint meters, JMDL-32XXAT bedrock meters, JMDL-49XXAT formwork meters, JMDL-52XXADT differential meters, JMCW-21XXADT magnetostrictive meters, and JMLS-22XXADT wire rope sensors. On site, this means one product group can cover bridge joints, tunnel portals, slope movement, dam deformation, railway subgrade settlement, and industrial linear motion. The value is not only the displayed millimeter reading. It is the ability to connect movement, time, temperature, construction activity, and warning limits into one record. The point should be named on the drawing, linked with its cable route, and checked against the expected movement direction before the first automatic reading is accepted. For daily review, the reading should be compared with nearby points, recent weather, site operations, and any loading event that could explain the movement.
FAQ
Q: Which Crack Meter are used for rock layers or bedrock?
A: JMDL-31XXAT multipoint meters are used for different surrounding rock layers, while JMDL-32XXAT single-point bedrock meters are used for tunnel rock mass, dam bedrock, slope, or foundation pit movement.
Q: How many points can the multipoint meter support?
A: The multipoint installation kit supports three to five monitoring points, with anchor heads fixed at different depths by drilling and grouting.
Q: What ranges are listed for these models?
A: Both JMDL-31XXAT and JMDL-32XXAT list 50 mm, 100 mm, and 200 mm models with 0.01 mm resolution.
Q: Why monitor several depths?
A: Different layers may move differently. Separating shallow and deep movement helps engineers judge whether the problem is surface creep, deeper rock slip, or overall mass movement.
Q: What records should be kept?
A: Keep drilling depth, anchor location, grouting date, channel name, zero value, cable route, and first stable reading.
Reviews
David Wilson
We purchased displacement transducers and settlement sensors, and the quality exceeded our expectations. Easy installation and reliable performance.
Joshua Clark
We ordered a full monitoring solution including sensors and data loggers. Everything works seamlessly together. Great supplier!
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