| 摘要 |
<p>An opacity measuring system for measuring opacity of smoke in a smoke stack or other effluent conveying pipe, in which light is transmitted from a light source chamber through the smoke or effluent to a chamber containing a photo-electric sensing device, separate moving Mylar tape windows being continuously moved past ports of the light and sensing chambers to provide continuous isolation of these chambers from the smoke or effluent via an always clean window into and out of the stack, thereby to prevent contaminations which would introduce errors in measuring opacity. Light is directed via two paths from one common light source in one chamber to two adjacent photo-cells in another chamber, one path extending through the smoke or effluent and the other via a fiber optic light pipe exclusive of the smoke or effluent, and the outputs of the two photo-cells are compared in a differential amplifier to provide an accurate measurement of opacity compensated for variations in the intensity of the source, the amplifier being powered by a regulated voltage supply, as is also the light source, to maintain accuracy of measurement despite normal line voltage variations.</p> |
