Abstract: A reflective wetting or spot detecting system incorporates a light emitting diode and a solid state photo sensor arranged on the same side of a medium being analyzed. The sensor is carried at one end of an elongated housing with a linear channel extending through. The channel is oriented on a line that is normal to the medium being analyzed. The channel functions as a lensless, passive focuser of reflected radiant energy. The source of radiant energy is located at an acute angle with respect to the medium. A conditioning circuit is coupled to the output of the sensor. The conditioning circuitry includes a current-to-voltage converter, a signal reducing stage, an amplifying stage and a comparator. The signal reducing stage reduces the voltage signal, produced by the current voltage converter, a predetermined amount, thereby effectively providing the amplifier stage with a greater dynamic range than it would have otherwise had.