[EMAIL PROTECTED] wrote: > > In a message dated 8/18/2002 5:05:31 PM Eastern Daylight Time, > [EMAIL PROTECTED] writes: > > > Comparing it to my Spotmatic the baseplate looks exactly > > the same size with everything in the same place. Has anyone tried fitting a > > K1000 baseplate to a Spotmatic to enable the use of the readily available > > s76/ LR44 battery? > > > > Very interesting..But even if you could , the Spotty wont be happy. > Spotmatics are designed for 1.35V mercury batteries. These cells > were very well suited for small electronic devices because they delivered > their current via consistent 1.35V for most of their effective lifespan. > LR44 size alkalines deliver 1.5V very inconsistently.They are "hot" > for about 3 mos then deteriorate fairly rapidly.As they age they will > deliver less and less current UNDER LOAD although they test "good" > on a battery tester (light load). LR44 size SILVER OXIDES like the > excellent Everyready #357 begin life at 1.55V and can deliver consistent > current for most of their lifespan. List members with bodies using LR44 > type cells should use SILVER OXIDE cells for more consistent results. > Unfortunately SilverOxide cells will deliver TOO much current for your > Spotty's meter. By the formula: > E = I x R ( E=volts, I = current, R=resistance) > the Spotty meter (the "R" of the formula) gets 1.55/ 1.35 or 15% too > much current....
No ~ too much voltage. 1.55 and 1.35 is voltage, not current. Further more, a load "draws" current, depending on the resistance of the circuit. Lower the resistance, the load will draw less. If you have a sufficiently robust power supply, it will deliver whatever current your load requires. No more, no less. Another furthermore...the Spotty F doesn't care, as it has a circuit that more or less ignores the input voltage, and supplies what the load requires. It requires 1.35 volts, and if you give it 1.50 volts, it still only supplies 1.35 volts to the load. IOW, it 'regulates' the output. I think that's the only Spotmatic that does that. > For you Spotmatic guys, a reasonable alternative is the 1.4V Zinc-Air > type hearing aid batteries.They are small so require a home-made little > washer to hold them in the chamber. Unfortunately their lifespan is very > limited ( 2 months?) and the Spotty meters work them HARD. > Regards, > Bob Varta imports a battery, the V625U, an alkaline battery that's nominal voltage is 5.0 VDC. Works just fine in my F. Oh, and by the way, it's outside diameter is exactly the same as the mercury battery was, so it fits just fine! No adapters needed. keith whaley - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
