| 摘要 |
A smoke meter where smoke flows between a light source and a photosensitive element which receives light from the light source, so that the extent to which light is received by the photosensitive element will be influenced by the opacity of the smoke. The light source is electrically connected to a meter which directly gives a reading of the opacity of the smoke. In order to compensate for any fluctuations in light other than the light travelling from the light source to the photosensitive element, a compensating lamp is provided to maintain at the photosensitive element a constant light level by compensating automatically for any fluctuations in light other than the light travelling from the light source to the photosensitive element, so that the latter will respond only to variations in light from the light source to provide an accurate indication of the opacity of the smoke.
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