Metal detection circuit
US5025227A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 11, 1989 |
| Grant date | Jun 18, 1991 |
| Priority date | — |
| Expiry date | Oct 11, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/9547
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Metal detection apparatus comprises an oscillator circuit including an inductive detection coil and a detector for rectifying the output of the oscillator circuit synchronously with the frequency of oscillation. A comparison circuit compares the rectified output of the oscillator circuit with a reference signal and generates an output signal having a value related to the amplitude of the oscillator output. A feedback circuit generates a positive feedback signal and applies it to the oscillator circuit to maintain its oscillation at a predetermined amplitude under quiescent conditions. The circuit is largely immune to electromagnetic interference and temperature sensitive effects.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.