Borehole survey instrument control circuitry
US4480391A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 3, 1982 |
| Grant date | Nov 6, 1984 |
| Priority date | — |
| Expiry date | Dec 3, 2002 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B47/022
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A borehole survey instrument and control circuitry are described. The borehole survey instrument includes indicators for measuring angle of deviation from the vertical and angle of deviation from magnetic north and a photographic recording means for recording the output of the indicators at selected times. A lighting system is utilized in conjunction with the photographic recording means to expose photographic film and a novel time control circuit is utilized in conjunction with the lighting system to alter the length of time of illumination in accordance with the operativeness of individual bulbs within the lighting system. In this manner, the failure of one or more bulbs within the lighting system will not substantially affect the amount of illumination to which the film in the photographic recording means is exposed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.