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凤凰304A是一种测光、闪光一体型照相机,其测光电路及闪光电路是各自独立的两部分。均内藏于相机体内,电路原理如图1所示。一、工作原理 1.测光电路:VT1、VT2等组成变态施密特触发电路,采用双LED跳闪灯指示被测光线的强弱。测光元件RG使用硫化镉(CdS)光敏电阻,其阻值随被摄景物反射光线强弱变化,感测的光线越强阻值越小,光线越弱阻值越大。RP是校准电位器,调RP可改变测光灵敏度。
Phoenix 304A is a metering, flash integrated camera, metering circuit and flash circuit are two independent parts. Are hidden in the camera body, the circuit shown in Figure 1. First, the working principle 1. Photometry circuit: VT1, VT2 and other components composed of abnormal Schmitt trigger circuit, using double LED flashing light indicates the strength of the light measured. Photometry RG uses cadmium sulfide (CdS) photoresistor, the resistance changes with the reflected light intensity of the scene, the stronger the light is, the smaller the resistance is and the weaker the light is, the larger the resistance is. RP is the calibration potentiometer, adjust the RP can change the metering sensitivity.