Development of sensors to detect the location and depth of hard pans in real time is a major restriction on the application of Site Specific Crop Management (SSCM). In this study, a soil compaction profile sensor equipped with four horizontal operating penetrometers for on-the-go sensing and mapping of the location and intensity of hard pans artificially formed in a soil bin was developed and tested. The leading edge of a 600 mm long vertical soil cutting blade held four 8 mm diameter, 80 mm long, and 30 degree conic tip stainless steel soil penetrating rods equally spaced at 100 mm vertical intervals. With this arrangement, when the cutting blade was driven into the soil up to a 500 mm depth, the conic tips sensed soil penetration resistances at 100, 200, 300 and 400 mm depths. The penetration resistance force was transmitted by the rod end to the elastic diaphragm of a hydrostatic oil chamber beneath each rod. Each oil chamber was connected to a force magnifying piston and cylinder located off the soil engaging tools. The penetration force was magnified five times before being sensed by a strain gage load cell. Software programs with the capability of discriminating 16 levels of soil compaction intensity were developed for monitoring soil impedances sensed by the soil probes and for converting them to soil compaction maps. For conducting the tests in the soil bin, the sensor mounted on the tool carrier frame was moved along the bin, where artificially formed compacted soil blocks with various densities (1.45, 1.65 and 1.85 Mg/m3) were placed at different locations and depths (up to 500 mm deep at 100 mm increments). While the probe was cutting and advancing through the soil, the corresponding compaction map was simultaneously displayed on a PC monitor, and the soil penetration resistance data of all four sensing tips was displayed and stored in program files.