Method for operating a metal detector and metal detector
AssigneeMettler-Toledo Safeline Ltd.
InventorPeter Howard
Life of this patent
Estimating the term…
Abstract
A metal detector apparatus having a balanced coil system, a receiver unit, a drive coil with at least one capacitor forming a series resonant circuit connected to a transmitter unit having a converter, and a drive controller. The metal detector apparatus configuration generates a first square wave signal set to a fixed/selectable operating frequency which is applied to a first drive switch connected on one side to a first voltage potential and on another side to a centre tap of a half-bridge circuit. A second square wave signal set is generated to the fixed/selectable operating frequency and is applied to a second drive switch connected on one side to a second voltage potential and on another side to the centre tap, via which a drive current is supplied to the drive coil.
Claims20
A method for operating a metal detector having a balanced coil system with two detection coils connected to a receiver unit and inductively coupled with a drive coil, which together with at least one capacitor form a series resonant circuit, the series resonant circuit being connected to a transmitter unit having a converter with a first drive switch and a second drive switch that form a half-bridge circuit, the method comprising:
- driving the series resonant circuit by a drive controller:
- in accordance with a first square wave signal (d1) that is set to a fixed operating frequency (fTX) and is applied to the first drive switch, which is connected on one side to a first voltage potential (VD) and on the other side to a centre tap of the half-bridge circuit;
- and
- in accordance with a second square wave signal (d2) that is set to the fixed operating frequency (fTX) and is applied to the second drive switch, which is connected on one side to a second voltage potential (VS) and on the other side to the same centre tap of the half-bridge circuit, via which a drive current (iD) is supplied to the drive coil;
- providing the first voltage potential (VD) and the second voltage potential (VS) with different magnitudes with reference to ground;
- providing the first square wave signal (d1) with a variable first duty factor and the second square wave signal (d2) with a variable second duty factor in such a way that the first square wave signal (d1) and the second square wave signal (d2) are never active at a same time;
- and
- adjusting the first duty factor and the second duty factor to set a coil current (iL61) in the drive coil to a value for operating the metal detector at the fixed operating frequency (fTX) and for measuring contaminants.
A metal detector, comprising:
- a balanced coil system with two detection coils;
- a receiver unit connected with the balanced coil system and inductively coupled with a drive coil, which together with at least one capacitor form a series resonant circuit;
- a transmitter connected with the series resonant circuit, the transmitter having a converter with a first drive switch and a second drive switch that form a half-bridge circuit;
- and
- a drive controller configured for generating and driving the series resonant circuit with:
- a first square wave signal (d1) that is set to a fixed operating frequency (fTX) for application to the first drive switch, which is connected on one side to a first voltage potential (VD) and on the other side to a centre tap of the half-bridge circuit;
- and
- a second square wave signal (d2) that is set to the fixed operating frequency (fTX) for application to the second drive switch, which is connected on one side to a second voltage potential (VS) and on the other side to the same centre tap of the half-bridge circuit, via which a drive current (iD) is supplied to the drive coil;
- wherein the first voltage potential (VD) and the second voltage potential (VS) are set to different magnitudes with reference to ground;
- wherein the first square wave signal (d1) is selected to have a variable first duty factor and the second square wave signal (d2) is selected to have a variable second duty factor selected such that the first square wave signal (d1) and the second square wave signal (d2) are never active at a same time;
- and
- wherein the drive controller is configured to adjust the first duty factor and the second duty factor to set a coil current (iL61) in the drive coil to a value for operating the metal detector at the fixed operating frequency (fTX) and for measuring contaminants.
Dependencies are inferred from the claim text.