Induction balance metal detector with inverse discrimination
US4024468A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 18, 1975 |
| Grant date | May 17, 1977 |
| Priority date | — |
| Expiry date | Jun 18, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/107
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An induction balance metal detector is described which is capable of discriminating between different types of metal objects, such as bottle caps and coins, by amplitude discrimination of their corresponding receive signals. In addition, the detector is provided with a tuning control which is used to eliminate the effect of ferrous mineral soil on the output signal of the receive coil. The discriminate control changes the phase of the residual output signal of the receive coil to set the quiescent operating point of the metal detector to a selected angle between about zero and -90.degree. relative to the component of the receive coil signal produced by the presence of magnetic mineral soil, and the tuning control adjusts the amplitude of the residual signal to an audio threshold level. As a result, the desired coins or other high conductivity metal objects reduce the amplitude of the received signal below the audio threshold level so that they tend to produce no sound output or a negative indication while all other objects increase the amplitude of such signal above the audio threshold level so they tend to produce a sound output. This inverse discrimination is provided with a posi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.