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Peter Wallage
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 12, 2004 - 02:39 pm: | 
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Hi all,
Does anyone know if it's possible to test a selenium cell from a lightmeter using a multimeter with a 200 ua setting? If so, would you have to put a resistor in series so that the cell's delivering current to something, what would be an order of magnitude for the resistor, and what sort of current reading should you get?
Peter |
Stuart Willis
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 15, 2004 - 06:01 am: |
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Test for voltage generation - not current.
This will tell you whether the cell is dead or alive. If alive - then what are its readings compared against a known accurate reference meter? From that point you can substitute lower value resistors in order to achieve accuracy. The accuracy may or may not be linear across the Light Value capacity of the selenium meter - but usually is is near enough to make no practical difference. |
Peter Wallage
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 20, 2004 - 09:21 am: |
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Thanks, Stuart.
I tested the cell from a 'dead' Weston Master II for voltage. It gave a reading, but fluctuating and not very consistent as I couldn't easily hold a good contact with the probe. However, I cleaned the contact 'ring' round the cell where the brass serrated ring makes contact, and the surface of the ring itself, with contact cleaner, and put it togther again. It worked!! According to a Gossen which I've got the Weston is now about one stop 'slow' over the whole range, but rather than strip it again and play with resistors I can use it by altering the ASA setting.
Once again, thanks.
Peter |
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