Alarm detector responsive to rate of change of a monitored condition
AssigneeCommissariat a l'Energie Atomique
InventorsDaniel Barbier, Jean-Michel Ittel, Robert Poujois
Life of this patent
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Abstract
A physical quantity such as temperature, infrared radiation or smoke is detected by means of a conversion device for emitting an alarm signal whose amplitude is representative of the intensity of the physical quantity. The detector comprises a unit for measuring relative variations of the signal in time, for comparing them with a preset threshold level and for actuating the alarm when they exceed the threshold level.
Claims15
An alarm detector comprising:
- a sensing device for converting a physical quantity to be detected into an electrical signal whose amplitude is representative of the intensity of said physical quantity,
- means for measuring the rate of change of said electrical signal during a predetermined time period,
- means for comparing the measured rate of change of said electrical signal with a preset threshold level, and
- means for actuating an alarm when said measured rate of change exceeds said threshold level.
An alarm detector comprising:
- a sensing device for converting a physical quantity to be detected into an electrical signal whose amplitude is representative of the intensity of said physical quantity,
- means for converting said signal into a second signal whose frequency is proportional to the amplitude of said signal,
- means for measuring the rate of change of said second electrical signal during a predetermined time period,
- means for comparing the measured rate of change of said second electrical signal with a preset threshold level, and
- means for actuating an alarm when said measured rate of change exceeds said threshold level.
An alarm detector comprising:
- a sensing device for delivering an electric current whose amplitude is a function of the temperature,
- means for converting said electric current into an electrical signal whose frequency is proportional to the amplitude of said electric current,
- means for measuring the rate of change of said electrical signal during a predetermined time period,
- means for comparing the measured rate of change of said electrical signal with a preset threshold level, and
- means for actuating an alarm when said measured rate of change exceeds said threshold level.
An alarm detector comprising a sensing device which delivers a current whose intensity is substantially proportional to the infrared radiation received by said device, and a processing assembly which is capable of actuating the alarm if said current varies at a characteristic frequency F.
An alarm detector comprising a first sensing device for delivering a first current whose intensity is proportional to the temperature, a first assembly for converting said first current into a first electrical signal whose frequency is proportional to the intensity of said first current, a second sensing device for delivering a current whose intensity is proportional to the cumulative effect of the temperature and of the infrared radiation received by said second sensing device, a second assembly for converting the second current into a second electrical signal whose frequency is proportional to the intensity of said second current, means for generating a third electrical signal whose frequency is equal to the difference in frequencies of the first two electrical signals, the two conversion assemblies being identical, and a processing assembly which is capable of actuating the alarm if the variations in frequency of the third electrical signal takes place at a characteristic frequency F.
An alarm detector comprising:
- a sensing device which delivers a signal whose intensity is a function of a first physical quantity,
- means for converting said signal into an electrical signal whose frequency is proportional to the intensity of said signal,
- a first switch,
- a first bidirectional counter connected to the output of said means for converting by means of said first switch,
- a source of clock pulses,
- a second switch operable in synchronism with said first switch,
- a second bidirectional counter connected to said source of clock pulses by means of said second switch,
- means for closing said first and second switches for a predetermined time period during which said first and second bidirectional counters count in a first direction and for closing said first and second switches for a second time period during which said first and second bidirectional counters count in a second direction, said second time period ending when said first bidirectional counter reaches a zero count,
- means for comparing the count remaining in said second bidirectional counter at the end of said second time period with a preset value N, and
- an alarm means which is triggered when the comparison of the count remaining in said bidirectional counter exceeds the value N a predetermined number of times consecutively.
Dependencies are inferred from the claim text.