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     Winfried Rating: N/A |
CdS photo resistors typically have very high resistance (more than 1 MOhm) in darkness - that's why many cameras do not have a meter switch, they are virtually switched off as soon as you block the light with a lens cap. Usually the resistance at 100 lux is indicated in CdS data. However, it is just a game of luck to find a suitable one. RS, Farnell and other electronic components suppliers still have CdS cells, mostly in a case design identical to that used on many cameras. BTW cadmium (one ingredient of these cells) will be banned in the near future, so probably noone will make CdS resistors any more. Hamamatsu has designed a photodiode-amplifier arrangement which is supposed to work as a replacement. |