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crack meters
Kingmach crack meters include the JMDL-31XXAT Smart Multipoint Displacement Meter for tunnels, rock slopes, foundation pits, and surrounding rock layers. The product uses displacement gauges, PVC measuring rod protective tubes, anchor heads, and multipoint installation kits that support three to five monitoring points. Installation is performed by drilling and grouting, with anchor heads fixed at different depths so each layer can be observed separately. Listed models include 50 mm, 100 mm, and 200 mm ranges, all with 0.01 mm resolution. The sensing principle uses an LC oscillation circuit: as the measuring rod moves inside the coil, magnetic reluctance and inductance change, causing the output frequency to change in a linear relationship with displacement. Because the rod and coil work without contact, the structure is less vulnerable to mechanical damage during installation. The built-in memory stores model, serial number, calibration coefficients, and up to 600 measurement records for later traceability. During project setup, the measuring point should be matched with the expected travel direction, available mounting space, cable route, and required acquisition interval. This prevents a short-range joint instrument from being used on a long-travel point, or an exposed sensor from being placed where an embedded anchor is needed. It also helps the monitoring team set a baseline that can be defended during acceptance and later maintenance review.
Application of crack meters
In railway and highway subgrade monitoring, crack meters are used to observe geogrid deformation, embankment movement, track foundation displacement, culvert joint movement, and settlement-related structural shifts. The field problem is that deformation may occur inside reinforced soil or pile-net foundations where visual inspection cannot reach after backfilling. Kingmach JMDL-24XXAT flexible displacement meters are designed for geogrid materials in reinforced soil and pile-net subgrade foundations. The bendable measuring rod can deform with the geogrid, while both ends are clamped using mounting brackets. Listed ranges are 30 mm and 50 mm, with 0.01 mm sensitivity, 0.5%FS accuracy, 20-point curve fitting, and a designed service life up to 30 years. For larger movement, JMLS-22XXADT wire rope sensors and JMDL-49XXAT formwork or steel wire meters can support long-distance displacement monitoring. These readings help maintenance teams connect settlement, traffic load, rainfall, and construction records. During operation, the monitoring team should keep the baseline, temperature, inspection notes, and nearby sensor behavior in the same review file. This makes it easier to tell whether a movement trend comes from normal service, a repair event, changing load, water influence, or developing structural risk. Clear records also help owners decide when a field inspection is needed instead of waiting for visible damage.
The future of crack meters
Future crack meters will also become easier to install in cramped and irregular field locations. Many monitoring points are not clean laboratory setups; they are narrow tunnel headings, wet dam galleries, crowded bridge joints, temporary formwork frames, steep slopes, and machinery spaces with limited room for tools. Smaller housings, clearer mounting accessories, stronger cable exits, and simpler alignment checks will reduce installation errors. Kingmach already uses several physical formats, including crack gauges with measuring rods and bases, draw-wire sensors for longer travel, embedded bedrock assemblies, flexible geogrid meters, and non-contact magnetostrictive meters. Future product development can make these formats more modular, so engineers select the mounting kit, cable protection, connector type, and acquisition method together. That would shorten commissioning time and make later maintenance less dependent on the original installer. For projects with many measurement points, practical installation improvements can be as important as another decimal place of resolution, because a well-mounted sensor gives cleaner data from the beginning.
Care & Maintenance of crack meters
For magnetostrictive crack meters, maintenance should protect the non-contact sensing advantage by keeping wiring, power, and mounting clean. Kingmach JMCW-21XXADT lists DC24V input, RS485 communication, IP67 protection, reverse polarity protection up to -36V, and wiring colors for power and RS485 lines. Confirm red, yellow, blue, and green wires before energizing the device, and check grounding in cabinets where motors, pumps, or hydraulic equipment may create electrical noise. Because the sensor is used for absolute position measurement over 0 to 1000 mm, inspect mechanical alignment and travel stops so the moving part remains within range. Do not clamp the sensing body in a way that transfers bending force from the machine frame. During service, compare repeatability at known positions and review whether position drift appears after temperature swings, maintenance work, or hydraulic cylinder repair. 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 meters
crack meters 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 meters fit crack monitoring?
A: The JMDL-22XXAT Smart Crack Gauge is designed for cracks, joints, and expansion joints in bridges, buildings, roads, railways, dams, tunnels, and slopes.
Q: What ranges does the crack gauge list?
A: Listed models include 20 mm, 50 mm, 100 mm, and 200 mm ranges, with 0.01 mm resolution on the 20 mm to 100 mm versions and 0.05 mm on the 200 mm version.
Q: How many records can the crack gauge store?
A: Product information states that it can save up to 600 measurement results, including time, temperature for temperature versions, displacement values, and zero-point value.
Q: What installation details matter most?
A: Base stability, rod alignment, connector sealing, cable protection, and a clear zero reading matter more than a polished-looking installation.
Q: Can it be used for long-term observation?
A: Yes. The product is described for long-term monitoring, especially where crack width changes need stable and repeatable measurement.
Reviews
Matthew Garcia
Instrumentation cables are durable and perform well even in harsh environments. Will definitely order again.
Joshua Clark
We ordered a full monitoring solution including sensors and data loggers. Everything works seamlessly together. Great supplier!
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