Ferrous/non-ferrous metal detector using sampling
US4110679A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 9, 1977 |
| Grant date | Aug 29, 1978 |
| Priority date | — |
| Expiry date | Jun 9, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/107
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A metal detector for detecting and distinguishing between ferrous and non-ferrous objects in an area which may contain a ferrous, mineralized soil background is disclosed. The hysteresis effect is used to distinguish between ferrous and non-ferrous objects by generating groups of transmit current pulses, each group including a polarizing pulse of one polarity followed by a pair of read pulses of the opposite polarity and less magnitude. The transmit pulses are applied to a transmit coil to induce corresponding receive voltage pulses in a receive coil. A pair of receive pulses corresponding to the read transmit pulses are fed through a low pass filter and thereafter sampled to produce a sample output signal corresponding to the difference between the sampled voltage levels of the pair of receive pulses. Control means are provided to adjust the sampling times such that when the metal detector is placed over an area containing a ferrous, mineralized soil background and no metallic objects, the sample output signal will be a constant D.C. voltage. This eliminates the effect of mineralized soil, which otherwise tends to prevent the detection of metallic objects. Thereafter, as the metal…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.