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crack gauges
Kingmach crack gauges include the JMCW-21XXADT Magnetostrictive Displacement Meter for absolute linear position measurement. This sensor uses magnetostrictive effect and internal non-contact sensing, which avoids mechanical wear and supports continuous operation in harsh environments. Product information lists 0 to 1000 mm measuring range, 0.01 mm resolution, plus or minus 0.05%FS accuracy, repeatability within 0.1 mm, DC24V plus or minus 10% input, RS485 communication, average operating current below 60 mA, and an operating temperature range from -30 degrees Celsius to +80 degrees Celsius. It also lists IP67 protection and reverse polarity protection up to -36V. Wiring details include red for DC24V, yellow for power ground, blue for RS485A, and green for RS485B. These features make the product suitable for hydraulic cylinders, gate position, machine stroke, structural deformation, railway and highway movement, retaining walls, and industrial automation equipment that requires stable absolute position data. 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 gauges
In integrated structural health monitoring, crack gauges 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 gauges
The future of crack gauges will put stronger emphasis on installation metadata. Many errors in displacement monitoring begin before the first reading: wrong range, poor bracket alignment, cable tension errors, unprotected connectors, zero readings taken during unstable loading, or channel names that do not match drawings. Kingmach smart displacement products store sensor data and measurement records, and future workflows can add digital installation forms, photos, QR codes, baseline checks, and automatic range verification. A field technician could scan the sensor, confirm whether it is a 50 mm, 100 mm, 200 mm, 1000 mm, or 2000 mm model, then bind it to the monitoring point. That small process improvement can prevent costly confusion months later, especially in projects with many cracks, joints, anchors, geogrid points, and rock-layer measurement depths. 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 gauges
For flexible geogrid crack gauges, installation care is more important than later access because the product may be buried inside reinforced soil. Kingmach JMDL-24XXAT uses a bendable measuring rod, 30 mm and 50 mm ranges, 0.01 mm sensitivity, 0.5%FS accuracy, 20-point curve fitting, and a designed service life up to 30 years. Both ends of the geogrid should be clamped with the flexible sensor sections using mounting brackets so deformation transfers reliably. Avoid sharp bending, cable tension, bracket slippage, and damage during filling or compaction. Record the geogrid layer, chainage, depth, sensor direction, zero value, and backfill date. During operation, compare displacement with settlement and rainfall records. If the trend changes after heavy rain, traffic loading, or nearby excavation, inspect accessible cabinets and cables before deciding whether the buried geogrid movement itself has changed. 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: What are crack gauges used for?
A: They measure movement such as relative displacement, crack width, expansion joint travel, bedrock deformation, rock layer movement, geogrid deformation, formwork settlement, and equipment stroke.
Q: Which Kingmach models belong to this category?
A: Common models include JMDL-21XXAT, JMDL-22XXAT, JMDL-24XXAT, JMDL-31XXAT, JMDL-32XXAT, JMDL-49XXAT, JMDL-52XXADT, JMCW-21XXADT, and JMLS-22XXADT.
Q: What range should be selected first?
A: Start from the expected movement. Short joint monitoring may need 20 mm to 100 mm, while draw-wire or equipment travel may require 500 mm to 2000 mm.
Q: Can these products support remote monitoring?
A: Yes. Several Kingmach models support digital transmission, RS485 communication, automatic acquisition, integrated testers, or unattended monitoring systems.
Q: Why is the baseline reading important?
A: All later movement is compared against the starting point. The baseline should be recorded after the sensor, bracket, anchor, cable, and structure are stable.
Reviews
Ryan Lewis
Fast delivery and excellent product quality. The accelerometers and tiltmeters are highly reliable. Strongly recommend this company.
Christopher Martinez
Very satisfied with the readouts & data loggers. User-friendly interface and supports multiple sensor inputs.
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