Prima 100 Portable Falling Weight Deflectometer

Prima 100 Portable Falling Weight Deflectometer

supplied with 100mm & 300mm loading plates, 10 kg weight, integrated load cell & centre-mounted geophone

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Using a portable falling weight deflectometer, PRIMA 100 LWD, is the fastest, easiest and most secure way of bearing capacity determination and quality assurance of unbound layers. The SL440 measures the surface modulus and presents results immediately to allow decisions to be made on site.

The PRIMA 100 reads out your results at once. Results are stored automatically together with the GPS position.

Measuring applied stress is important

The PRIMA 100 is the only LWD utilising the technique from the big traditional falling weight deflectometers with an integrated load cell. Consequently the PRIMA 100 registers the variation of the applied stress transferred to different (sub)soils using the same weight drop height. A variation that may be substantial and therefore has to be taken into consideration to achieve reliable E0 results and hence to make the correct conclusions.

Data presentation/documentation

After a measuring campaign or any time during a campaign, data can be seen on the display. Either each individual drop
or the entire series of measuring points. Data can be transferred to Excel or Word. This allows printing of data for further interpretation or direct presentation in a report as documentation towards e.g. a client. 


  • The PRIMA 100 method is quicker than the isotope measuring method and requires no reference measurements
  • The equipment has no radioactive sources requiring safety courses
  • PRIMA 100 applies wireless technology for data collection and is one-man operated
  • Easy power supply Four ordinary AA batteries supply power to electronics and display.
  • Extension to three geophones is possible.

The equipment

SL440 is supplied with 100 mm and 300 mm diameter loading plates, a 10 kg weight, integrated load cell and electronic
box and a centre-mounted geophone.
A portable PC or a PDA with a data collection program installed is required. See SL435