Deteriorated filament detection
AssigneeSafegate International AB
InventorÅke Pettersson
Life of this patent
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Abstract
A Method and an arrangement providing detection of deteriorated lamp filaments (3) in a lamp circuit (11) fed by constant current, in particular for a lamp supervision system for airfield lights. A change in a constant current fed through a lamp circuit (11) is initiated, whereby the lamp filament resistance is determined once in conjunction with the change in current and once a time period later. A difference between the resistance determinations constitutes the deterioration of a lamp filament (3) in comparison with a threshold value. Hence, no record of previous resistance determinations have to be stored, and lamps (4) can be replaced when the difference matches the threshold value.
Claims20
A method providing detection of deteriorated lamp filaments (3) in a lamp circuit (11) fed by constant current from a switching or regulating device, characterized in determining a resistance value across the lamp circuit once in conjunction with a current change caused by the switching or regulating device and once a predetermined time later, whereby the difference between the resistance determinations constitutes the deterioration of a lamp filament (3) in comparison with a threshold value for said difference, thereby avoiding a record keeping of previous resistance determinations.
A monitoring arrangement providing detection of deteriorated lamp filaments (3) in a lamp circuit (11) fed by constant current from a switching or regulating device, characterized in that it comprises:
- lamp monitoring means (10) connected to said lamp circuit (11), which detects that a change in said constant current is caused by the switching or regulating device to flow through said lamp circuit (11);
- resistance determining means, which determine a resistance value across said lamp circuit (11) once in conjunction with said current change and once a predetermined time period later;
- difference determining means determining a difference value between said determined resistance values;
- evaluation means for evaluating said resistance difference value compared with a threshold value for said difference;
- and
- whereby the difference between the resistance determinations constitutes the deterioration of a lamp filament (3) compared with said threshold value (ΔTr), thereby avoiding a record keeping of previous resistance determinations.
Dependencies are inferred from the claim text.