Induction balance metal detector with ferrous and non-ferrous metal identification
US4300097A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 27, 1979 |
| Grant date | Nov 10, 1981 |
| Priority date | — |
| Expiry date | Jul 27, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/107
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An induction balance metal detector circuit includes a receiver coil output which is connected to one input of a unique phase detector circuit. The reference transmitter coil signal is connected to a second input of the phase detector. The phase detector comprises circuitry which provides an output equal to the smaller of the two input signals. The output is doubled and integrated, then compared to a current indicative of the integrated reference signal in a differential amplifier. The output of the differential amplifier is passed through a dead band and used to excite a first indicator in response to phase difference between the inputs to the phase detector indicative of the location of ferrous metals. A second indicator is excited in the event the phase difference indicates the presence of non-ferrous metals. A balance and threshold control is established between the transmitter and the receiver coils in order to adjust the phase and amplitude of the received signal. A feedback loop is established between the ferrous metal output and the threshold and the balance control. The ferrous metal output is integrated to provide an indication of mineralized soil in the environment. This…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.