A harness for a child is disclosed. The pad includes a surface such that as the pad is abraded the surface is renewed exposing at least a portion of the chemical agent. The plurality of sensors may be recalibrated when the plurality of sensors are not in use. The invention has the advantages of realizing high-degree top driving drilling simulation, enhancing the field sense for teaching and training, shortening the training period and reducing the training cost. The disturbance reducing interface may comprise a matrix of permeable material such as a mesh, foam, or other porous materials. The method multiplies each of the output values by the acquired weight to generate image data after color conversion.