Continuous normalizer for an electronic circuit that compensates for

Abstract

A normalizer for a machine sorting individual items from a stream flowing in a channel having a background with reflectivity characteristics substantially identical to reflectivity characteristics of acceptable items. A photodetector produces an output which is amplified in three stages of amplification, dc coupled together, the second stage having an input adjustment for producing a zero voltage output for channel background reflectivity only. The output used for sorting purposes includes both positive and negative peaks. However, to prevent such peaks from greatly influencing normalizing action, the output of the second stage is applied through a limiter, which substantially clips both the positive and the negative peaks, to an integrator, which produces an average reference input voltage to the operational amplifier. DC offset to the input of the operational amplifier or because of changing operational conditions within the circuit gradually change the reference input voltage to the operational amplifier to compensate or normalize for drifting conditions. Peaks that are indicative of items to be sorted are hence adjusted to the normalized zero output of the second amplifier.