Metal detector with circuits for automatically screening out the effects of offset and mineralized ground
US4783630A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 27, 1986 |
| Grant date | Nov 8, 1988 |
| Priority date | — |
| Expiry date | Mar 27, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/104
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A portable transmit/receive induction balance type metal detector having an automatic ground exclusion balance (GEB) feature to facilitate the screening out of the effects of mineralized ground. The circuitry provides a static GEB in a single try and then, if selected by the user, continual automatic GEB on a dynamic basis as the system is used. The circuit includes a pair of quadrature phase detectors, one of whose outputs is approximately in phase with the ground component of the loop return signal. That output is modified, during an air balance of the detector, to remove the residual offsets in the circuit. This modified output in turn is summed with the other phase detector output to produce a phase detection signal that can be adjusted by automatic means to be precisely in quadrature with the ground component of the loop return signal. A controller is provided, with selectable user inputs, to initiate the static and dynamic GEB operations. An error amplifier in conjunction with two sample/hold elements and a variable duty cycle chopper operate in a feedback loop to appropriately adjust the phase detection signal. Audible beep indications are generated to signal the user when t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.