| 摘要 |
PURPOSE:To maintain in the optimum way both a high selection factor and selection capacity of the grain with a high precision, by providing an automatic gain control circuit to the control circuit and then keep the steady and constant voltage at all times to the increment and decrement of the detection sensitivity of the photodetector. CONSTITUTION:The reference value for the selected different-color grains is set to setter 21 of control circuit 12. Then the raw grain is supplied to drive the automatic control device, and thus the reflected rays of the different-color grains are received by photodetectors 7A and 7B. And this detection signal is sent to circuit 12. Electromagnetic ON-OFF valve 13 of the jet nozzle device is actuated by the output signal of circuit 12 to select the different-color grains. In this case, automatic gain control device 23 gives compensaion to the output signal of differential amplifier 19 down to a certain value of the darkest color grain if the detection signals of 7A and 7B vary by the evaporation of water of the dust. Thus the steady value is secured for the output signal. As a result, the output signal sent from circuit 12 can always be kept steadily at a certain level of voltage and then made clear. With this signal, valve 13 can be switched smoothly and assuredly to ensure an accurate jet selecting action. Accordingly, both a high-accuracy selection factor and selection capacity can be maintained in the optimum way. |
