Method and apparatus for detecting the presence of a contaminant in a gaseous carrier
US4446720A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 25, 1981 |
| Grant date | May 8, 1984 |
| Priority date | — |
| Expiry date | Nov 25, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/0256
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The invention concerns the detection of contaminant in a stream of gas. Pious methods have either been insufficiently sensitive or have been slow and needed skilled operatives. The present invention allows speedy operation with relatively unskilled operatives. A piezo electrical crystal oscillator (1) is allowed to oscillate for a known period of time and the number of oscillations is counted. For a known time the crystal is exposed to contaminant, and is then allowed to oscillate again for the same period of time as before and the oscillations again counted. The difference in number of oscillations is a measure of the mass of contaminant deposited on the crystal (1). The period of oscillation of the first crystal is determined by a second matched crystal oscillator (2) in which the crystal is exposed to the same environment but not in contaminant. The apparatus has the advantage of being self-zeroing, and the exposed crystal (1) does not need cleaning after each use. The invention has special application to the testing of medical gases, for example oxygen and nitrous oxide.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.