The darkroom exposure meter circuit

Published:2011/8/23 22:06:00 Author:Borg | Keyword: darkroom, exposure meter | From:SeekIC

This exposure meter can not only measure the exposure time, but also indicate the difference in the relative photometry. In the circuit, D1 is the photoelectric diode, when it is shone by the light, it is generating a voltage which is amplified and phase-inverted by the 3-stage op-amps IC2, IC3 and IC4, the voltage is added on the serial circuit composed of the meter head M1, R18 and trimmer resistor P3, the application of the M1 dial is logarithm type. The diodes D2 and D3 are used to compensate the temperature voltage changes caused by the photoelectric tube, so it should be closed to D1 when we fix it.



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