Wavebounce is developing a new device intended for Q&A on asphalt pavements. Existing methods of measuring the electrical properties of pavements are extremely sensitive to the mechanical positioning of the apparatus on the pavement surface and thus give very erratic results. The new SPOT device senses the dielectric of the surface material by emitting a short pulse and measuring the amplitude of the return signal. Standard relations give the dielectric value in terms of the reflection coefficient. The total signal path length is over a meter and thus distance variations of millimeters due to positioning are inconsequential. This property makes this device much more repeatable than capacitance type devices whose outputs vary wildly with small displacements over the test surface. The difference can be dramatic when testing surfaces with texture.
The SPOT unit operates over 16 hours on internal D cells and is controlled by a PocketPC hand held unit. The PocketPC displays and records all results and communicates with the SPOT sensor unit via a wireless connection. A summary file of all measurements is produced in Excel format. A laptop PC can also be used to control/communicate with the SPOT device.
Field testing with SPOT on new asphalt paving jobs is now underway.
Note, by selecting an optional display mode, SPOT shows signals from below the pavement surface.
