EN
ar
bg
hr
cs
da
nl
fi
fr
de
el
hi
it
ko
no
pl
pt
ro
ru
es
sv
tl
iw
id
lv
lt
sr
sk
sl
uk
vi
et
hu
th
tr
fa
ms
hy
ka
ur
bn
mn
ta
kk
uz
ku
crack gauges
Kingmach crack gauges 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 gauges
In railway and highway subgrade monitoring, crack gauges 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 gauges
Longer service life will be a major future requirement for crack gauges. 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 gauges
For embedded crack gauges such as multipoint and bedrock displacement meters, maintenance depends heavily on installation records because the sensing parts may not be visible after grouting or backfilling. For JMDL-31XXAT multipoint meters, keep drilling depth, anchor head depth, grouting date, point number, cable route, and baseline readings in one record. The system may monitor three to five points, so channel naming must be exact. For JMDL-32XXAT single-point bedrock meters, record flange position, tie rod condition, anchor point, PVC pipe route, and expected movement direction. During service, compare adjacent depths rather than reading each channel alone. A shallow layer moving while deeper layers remain steady has a different meaning from full-depth displacement. Do not pull or shorten cables during cabinet work, and protect exposed sections from water, rodents, sharp edges, and construction traffic. 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 gauges
When a monitoring plan is built around crack gauges, the first question should be the engineering decision behind the reading. If the purpose is crack control, the JMDL-22XXAT series focuses on crack width, joints, and expansion joints. If the purpose is rock layer movement, the JMDL-31XXAT multipoint meter anchors several depths and separates displacement by layer. If the purpose is bedrock or slope face movement, the JMDL-32XXAT embedded single-point meter uses an anchor head, tie rod, flange, and PVC pipe assembly. If the purpose is large travel or equipment position, the JMLS-22XXADT wire rope sensor and JMCW-21XXADT magnetostrictive meter provide longer range options. Kingmach's category is therefore a toolbox for movement diagnosis, not one product renamed many times. That distinction helps engineers set warning values that match the structure being observed. 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 gauges handle long travel?
A: JMLS-22XXADT wire rope sensors cover 0 to 500 mm, 0 to 1000 mm, and 0 to 2000 mm ranges, while JMCW-21XXADT magnetostrictive meters cover 0 to 1000 mm absolute position measurement.
Q: What is the difference between wire rope and magnetostrictive types?
A: Wire rope sensors convert cable extension or retraction into displacement data, while magnetostrictive meters use non-contact sensing for absolute linear position.
Q: What protection ratings are listed?
A: Product information lists IP67 for the JMLS-22XXADT wire rope sensor and IP67 for the JMCW-21XXADT magnetostrictive meter.
Q: What communication is available?
A: Both products list RS485 communication, which supports digital connection to acquisition systems.
Q: Where are long-travel models used?
A: They are used in dam monitoring, geohazard prevention, machinery position, hydraulic cylinders, gate movement, tunnel clearances, and structural displacement between two points.
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!
Latest Inquiries
To protect the privacy of our buyers, only public service email domains like Gmail, Yahoo, and MSN will be displayed. Additionally, only a limited portion of the inquiry content will be shown.
Olivia***@gmail.comUnited States
Hello, we are currently sourcing high-precision strain gauges and load cells for a bridge monitoring...
Mia***@gmail.comNetherlands
Dear team, we are interested in your readouts & data loggers compatible with multiple sensors. Do yo...