| 摘要 |
A measuring head, e.g. for a smoke detector, includes a tubular holder (1) intended for being disposed in a ventilation duct for being passed through by the air which is to be monitored. The portion of the holder to be introduced in the ventilation duct is ended by an optical reflector (6) defining one end of a measuring path while the opposite defining surface of the measuring path includes a beam transmitting means and a detector means. The peripheral surface of the holder around the measuring path has a number, preferably six, of rows of holes (2) with at least six holes in each row. The holes in a row are staggered relative the holes in adjacent rows, the staggering amounting to between 1/4 and 1/3 of the hole width. At least 1/4 of the peripheral surface of the holder introduced in the ventilation duct and surrounding the measuring path is covered by the holes. |
