Metal detector having digital signal processing
US4709213A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 8, 1985 |
| Grant date | Nov 24, 1987 |
| Priority date | — |
| Expiry date | Jul 8, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/9525
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A metal detector circuit includes a transmit coil (12) and a receive coil (56) arranged in a balanced induction configuration in an electromagnetic field. The receive signal from the receive coil (56) is input to electronic switches (146, 148) which receive quadrature reference inputs from a phase shift circuit (112). The phase demodulated outputs of the switches (146, 148) are passed through amplifiers and input to an analog-to-digital converter (324) to produce digital signal samples which are transmitted through a bus (326). The bus (326) is connected to random access memory (414, 416) and a read only memory (418) which includes a stored signal processing program. A microprocessor (374) is connected to the bus (376) for receiving the digital signal samples and the stored program from memory (418). The microprocessor (374) executes the stored signal processing program to produce a digital output signal which is transmitted through the bus (326) to a digital-to-analog converter (360). The converter (360) produces an analog output signal which is passed to an output driver circuit which produces a target indication signal at a speaker (284). The digital signal processing provided b…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.