Apparatus for measuring a predetermined characteristic of a material using two or more wavelengths of radiation
US3965356A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 29, 1975 |
| Grant date | Jun 22, 1976 |
| Priority date | — |
| Expiry date | May 29, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/314
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Measuring apparatus is used as a control element to maintain the correct ratio of chlorine to pulp in a bleach plant. Two diffusing windows are used; one to randomly radiate electromagnetic energy into the pulp and the other to receive radiation from the bulk of the pulp and reradiate it. Two bands of radiation are examined; one in the visible and the other in the infrared. Rather than using a conventional beam splitter, two detection systems, differing only in their spectral pass band, are used. Their optical axes converge in the center of the receiving window so that identical images of the receiving window can be projected on each of the detectors. The detector system allows the use of interference type filters which require sensibly parallel radiation. In addition to sensing the brightness of pulp, which is affected by the amount of chlorine, the above apparatus is useful for concurrently measuring opacity, moisture content, and basis weight of a moving sheet. A single sided moisture gauge is also provided which eliminates the effects of flutter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.