Mobility is the ability to move freely and rapidly over the terrain of interest to accomplish varied off-road objectives. The vehicle weight and its footprint determine the resultant ground pressure that the vehicle imparts on the soil. The soil strength, coupled with the ground pressure, determines vehicle cone index, VCI, which is the key for vehicle mobility. The cone penetrometer is designed to give an index of soil strength where the operator will quickly shift his vision from the rod at

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... e ground to the dial at the proper moment, meanwhile maintaining a constant penetration rate; this may cause an error in reading and recording the results. A comparison of rating cone index RCI with the vehicle cone index VCI indicates whether the vehicle can negotiate the given soil condition for a given number of passes. In this paper an adaptation has been made to the standard cone penetrometer to become an electronic device. The proving ring is replaced with a load cell, and the depth of penetration in soil is measured with displacement transducer sensor. Then the applied force and the sinkage are automatically recorded on a data storage module and processed to obtain the rating cone index (RCI) of different soil. Three interfacing circuits to amplify the out voltage from load cell, displacement transducer and site number selector are designed. In the control unit, the microcontroller is coupled to an EEPROM (Electrically Erasable Programmable Read-Only Memory)to store the measured load and sinkage data. It has a capacity sufficient to store the measured data from different 12 sites. For each of them, 256 samples are sensed during test.