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Forum: Film SLRs and Compact Film Cameras 12-22-2017, 01:42 AM  
Asahi spotmatic sp battery recommendation
Posted By alastairnc
Replies: 73
Views: 149,346
According the info from Pentax, the meter (the circled M uppercase on the schematic) has an internal resistance of 3 Kohm. They also say that the needle is centered when a current of 3uA (microAmp?re) traverses the meter. Hence a higher voltage battery will give a higher current at centre, so the needle will be off!
Forum: Film SLRs and Compact Film Cameras 12-21-2017, 05:40 PM  
Asahi spotmatic sp battery recommendation
Posted By alastairnc
Replies: 73
Views: 149,346
No, the voltage does matter. The bridge is loaded by the asa resistance when balanced against the output of the cd cell at 1.35 volts. I did a side by side comparison and the results for 1.55 and 1.35 volts were hugely different. Also using a 1.55 volt battery and an external light meter also gave huge diifferences
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