Abstract
A null-reading photometer head is described which employs a Photox cell integrally mounted with a graphite-graphite commutator in such manner that the direct current in an external instrument is reversed synchronously with the exposure of the cell to standard and unknown source. The candlepower of a Mazda lamp may be read directly on a permanent scale.
© 1939 Optical Society of America
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Clifton Tuttle
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