Lightweight Deflectometer (LWD)


Lightweight Deflectometers (LWDs) are increasingly being used to determine overall compaction quality of all types of earthworks through their use as a QC/QA field test. LWDs provide a rapid determination of elastic modulus, which is an essential factor in mechanistic design and can be used as an accurate assessment of compaction. An LWD is used for measuring the bearing capacity (deflection) of subgrade/subsoils and unbound base layers, granular layers and backfilling materials, according to ASTM E2835-11. Based on the static plate load test requiring a load vehicle, the LWD provides a simple, fast and repeatable test providing an accurate assessment of compaction parameters. Applications for this non destructive method of testing include bearing capacity and compaction include road construction, pipeline and cable backfill, railway track beds, airport runway/taxiways, dam construction, embankments, foundations and other earthworks.

Humboldt offers two models of Lightweight Deflectometers from HMP- a deluxe model, the HD-4129.3F and a basic unit, the HD-4130.3F. Both units are the same mechanism and differ only in the controller used with each one.
The HD-4129.3F features a deluxe controller that includes:

  • a large, 3.5″ colorful display
  • light sensor-controlled backlighting that provides the optimum readability even in bright sunlight
  • easy menu navigation
  • integrated GPS
  • integrated WIFI-enabled
  • interface for a thermal printer and USB
  • help function
  • efficient and fast 32-bit processor
  • internal memory for up to 1000 tests
  • high-performance rechargeable battery

The graphic interface of the HD-4129.3F provides an intuitive menu, which guides the user through the testing procedure and provides real-time test results. Measured data is presented in tabular, as well as curve formats with date. time and GPS location clearly depicted. This data can be exported from the control unit via USB or wirelessly directly into the Cloud or to your PC for archiving and further processing. This allows personnel in any office to have access to data while you are still on site testing. It is also possible to print out results to a small portable printer on site.

Use of the web-based evaluation software: HMPreport, provides the ability to produce professional reports for each measuring point, which can include your logo and contact details. This software allows you to work with your data from the Cloud or your PC. The software also enables you to store the data in a database with easy-to-use search and editing options.

Units include:

  • The LWD
  • magnetic base plate
  • portable printer (USB)
  • GPS
  • PC Software
  • Android App (HD-4129.3F and HD-4149.3F only)
Additional Specifications
Electronic settlement measuring instrument HD‑4129.3F
Settlement measuring range 0,1 bis 2,0 mm ± 0,02 mm
Measuring range Evd < 225 MN/m2
Temperature range 0 to 40 °C
Very robust, splash-water proof, connection cable with high-quality LEMO connectors
Graphic display in mm 56 x 73 38 x 68
Colorful, lightsensor-controlled and illuminated
Help function
Fast, efficient 32-bit processor
Bluetooth, USB, thermal printer interface
Dimensions in mm 210 x 100 x 31 211 x 100 x 26
Storage capacity, internal in measurement series 1000 500
Power supply:
High-performance rechargeable lithium-polymer-battery 3,7 V, 6300 mAh
4 x R6 Batteries
Menu navigation (18 languages available)
Loading Mechanism
Total weight 15,0 kg
Drop weight 10,0 kg
Max. impact force 7,07 kN
Duration of impact 17,0 ± 1,5 ms
Material: zinc coated/hard-crome plated steel
Spring element 17 disk springs
Load plate
Diameter 300 mm, Plate thickness 20,0 mm
Total weight 15,0 kg, Material: zinc coated steel
The Lightweight Deflectometer (LWD) supports the following standards: ASTM E2835-11
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