Photomultiplier Tubes for Programmable Logic Controller Foreign Object Sorting System and Its Performance Analysis

Abstract

The photoelectric foreign object sorting system is a comprehensive device developed to remove foreign objects from target substances, integrating photoelectric, computer, and mechanical technologies. This system combines photoelectric, computer image, and mechanical technologies to identify materials based on color and appearance, utilizing the scattered light returned from the scanned object for detection and recognition. This work designs a photoelectric foreign object sorting system for food and tobacco. This system takes photomultiplier tubes as the main photoelectric devices and a programmable logic controller (PLC) as the control unit. The hardware components of this system include the design of a low-noise preamplifier, conditioning circuit, ADC data acquisition module, and PLC-external circuit connections. In simulation experiments, testing is conducted on the low-noise preamplifier, considering the significant impact of the collected signals on subsequent analysis. Amplitude-frequency and phase-frequency tests show that the circuit signal output of this module is stable. There are no oscillations in the time domain, and no occurrences of overshooting or ringing in frequency. The noise indicates that the signal noise of this module is relatively low. During the debugging process, ADA4896 is selected, and a black-and-white alternating stripe with a 3 mm spacing is used as the scanning object. As expected, the first-stage amplification results of the low-noise preamplifier show a range of 2 mV with some DC components in the output voltage. In its second-stage amplification, the fine scale reaches 10 mV, and the output signal can represent the physical characteristics of the scanned object.