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crack meters
The JMDL-52XXADT Differential Displacement Meter is one of the higher precision Kingmach crack meters for structural joints and relative movement. It uses two coupled inductive coils. As the measuring rod moves, magnetic flux changes in the two coils are equal in magnitude and opposite in direction, and the difference is calculated to reduce environmental interference and thermal drift. Listed ranges are 20 mm, 50 mm, and 100 mm. The product provides 0.01 mm resolution, plus or minus 0.1%FS accuracy, RS485 digital output, DC 9V to 24V supply, power consumption below 0.4 W, long-term stability of plus or minus 0.1%FS per year, and an operating temperature range from -40 degrees Celsius to +80 degrees Celsius. Temperature drift is listed as 0.001 mm per degree Celsius. These specifications are useful for bridges, railways, hydropower structures, dams, and buildings where small relative movement needs to be measured across seasons and load changes. 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 crack and joint monitoring, crack meters give engineers a direct view of width change rather than a note from visual inspection. This is important for bridges, buildings, tunnel linings, dams, road structures, railway structures, and slope retaining works where a crack may open, close, or move with temperature and load. Kingmach JMDL-22XXAT Smart Crack Gauge is designed for cracks, joints, and expansion joints, with listed 20 mm, 50 mm, 100 mm, and 200 mm ranges. Resolution is 0.01 mm for the 20 mm to 100 mm models and 0.05 mm for the 200 mm model, with 0.5%FS accuracy. Different measuring rods and universal bases allow the instrument to fit varied joint widths and installation angles. Stored model data, serial number, calibration coefficient, and up to 600 measurement records help teams compare early baseline values with later movement after traffic changes, rainfall, repair, vibration, or structural loading. 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
The future of crack meters in infrastructure will depend on better integration with digital twins and asset management records. A displacement reading becomes more useful when it is tied to a drawing location, construction stage, material zone, inspection photo, and repair history. Kingmach products such as JMDL-31XXAT multipoint meters and JMDL-32XXAT bedrock meters can represent movement at depth, while JMDL-52XXADT differential meters and JMDL-22XXAT crack gauges represent surface or joint movement. Future platforms can map these readings onto tunnel sections, dam galleries, bridge joints, or slope profiles, allowing engineers to see where deformation is growing. This is especially useful when movement is small but repeated. A millimeter trend may not seem urgent in one report, but over months it may show a clear relationship with rainfall, traffic, excavation, or water level. The strongest systems will still depend on careful installation, because digital tools cannot correct a loose bracket, wrong range, or poorly recorded baseline. Clear reporting will make displacement monitoring more useful for non-specialist decision makers while preserving the detail engineers need.
Care & Maintenance of crack meters
For crack meters 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 meters
crack meters give field teams a direct way to watch components that are hard to judge by sight. A formwork pipe may shift during pouring, a rock layer may slide behind the excavation face, a geogrid may deform inside reinforced soil, and a dam joint may open after water level change. Kingmach's product range includes non-contact designs where the measuring rod and coil work independently, reducing mechanical wear and installation damage. The JMDL-24XXAT flexible displacement meter uses a bendable measuring rod for geogrid monitoring, with 30 mm and 50 mm ranges, 0.01 mm sensitivity, and 0.5%FS accuracy. The JMDL-49XXAT formwork meter offers 50 mm, 100 mm, and 200 mm ranges, IP68 protection, and temperature measurement accuracy of plus or minus 0.5 degrees Celsius. These details are useful when displacement monitoring must continue through wet, crowded, and fast-moving construction stages. 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 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
Joshua Clark
We ordered a full monitoring solution including sensors and data loggers. Everything works seamlessly together. Great supplier!
Matthew Garcia
Instrumentation cables are durable and perform well even in harsh environments. Will definitely order again.
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