Exposure meters

I have a Gossen Luna Pro in which I use the battery adapter sold I think by B&H. I sent it to Quality Light Metrics a while back for service. It is about 2 stops off in part of the scale. I returned it, they checked it, said it was fine. However it remains 2 stops off. (I calibrate using Dr. Richard Henry's methodology) and Quality refunded my money. Does anyone know if this is a battery problem or ?

RJS said:

I calibrate using Dr. Richard Henry's methodology

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What is that calibration methodology? I assume that Quality Light uses accepted photometric standards against a NIST reference. If it has a traceable calibration I'd normally accept it to be "correct" (to the extent that the meter can correctly measure and what it measures) and re-examine my in-house testing method.

P.S.: The calibration is normally with the voltage as supplied. The Gossen does not have a balanced circuit and so must be calibrated with your adapter.

It would most definitely not be a battery problem. It sounds like either the calibration or photo cell may be damaged and is not picking up lower values properly.