| 摘要 |
<p>The circuit which measures, via a photocell, the time integrated energy of a photographic flash, and displays this on a suitable instrument, so that accurate exposures can more easily be obtained. The circuit operates by generating a voltage proportional to the logarithm of the time integrated energy received by a photodiode (3) exposed to the light produced by a switched (36) flash gun (37). The current produced in the photodiode (3) is amplified and gated by a suitable arrangement of transistors (4, 12, 13) and FET's (7, 8) with an adjustable timing circuit (32, 33) which can be used to reset the sensitivity of the device according to the film being used. A gauged switch (21, 22, 36) ensures that the flash (37) and timing circuit start together, while a galvanometer (A) gives a reading of the result obtained.</p> |
