As far as actually answering questions goes, I think that the batterless ones just have some appropriate detector connected to a moving coil galvanometer.
The detector squirts out some current, and the MCG moves a needle depending on how much current is squirted out. There are likely some variable resistors in there too, so that you can change ISO values for the film. From memory it was sorta sticking in places, so I suppose that something mechanical might be sticking, or there could be some intermittent fault with the bit of circuitry for changing the ISO values.
Or at least thats my best guess for someone who is off home about now :)
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timeasmymeasure
A physicist who answers questions on optics
Date: 2003-06-04 09:23 am (UTC)As far as actually answering questions goes, I think that the batterless ones just have some appropriate detector connected to a moving coil galvanometer.
The detector squirts out some current, and the MCG moves a needle depending on how much current is squirted out. There are likely some variable resistors in there too, so that you can change ISO values for the film. From memory it was sorta sticking in places, so I suppose that something mechanical might be sticking, or there could be some intermittent fault with the bit of circuitry for changing the ISO values.
Or at least thats my best guess for someone who is off home about now :)