Gossen Luna-Pro

[scott_hawranek]

I have an older Gossen Luna-Pro meter and it appears to be misreading

by at least one or two F-stops, relative to my friend's meter. I am

trying to flush out any user error, etc. b/f replacing it as I really

like the meter.

 

I think it may be a battery issue b/c when I test the battery the

needle moves past the read square by about the same amount as the

misreading. Currently, I am using two PX625S Alkaline Cell Batteries.

 

The outside of the of the battery holder calls for 2 Batt. 1.35V IEC

MR 9 and the user manual calls for Mallory PX 13 batteries, which I

believe are mercury batteries.

 

So, I guess I would like to know, if you think the batteries are the

issue and/or if so, where to buy them?

 

Also, I saw on your website:

 

http://gallery.bcentral.com/GID2025592P2757187-Replacement-Parts/Gossen/Battery-Kit-For-Gossen-Luna-Pro.aspx

 

Are these the correct batteries?

 

Thanks!!!

[skipd]

The problem is that the mercury batteries (which are outlawed in the US now) were 1.35 volts per cell. All modern batteries are approximately 1.5 volts per cell. Even though there may be newer 1.5V batteries that fit the old meter, the voltage difference will cause a severe calibration problem.

 

The old mercury batteries also had a characteristic which cannot be met with the current technologies, and that was the constant voltage output over the life of the battery. Modern batteries have a changing voltage over the life of the battery. Old meters depended on the mercury battery's voltage stability, and there were no voltage regulation circuits built into the old meters.

 

One solution might be found at this web site: http://www.classic-cameras.com/MR-9.htm

[scott_hawranek]

Thanks everyone, I bought Wein air cells, hopefully that resolves the issues.