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US 2012/0247183 A1Published application
Photoacoustic Detector with Acoustic and Vibration Noise Compensation
AssigneeHoneywell International Inc.
InventorTom M. Rezachek
Life of this patent
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Abstract
A photoacoustic detector includes a sensing region for receiving atmospheric samples. One microphone receives acoustic samples from the sensing region. Another microphone receives acoustic samples from a displaced region. Microphone outputs can be subtracted to eliminate common noise and to generate an indicium of gas present in the sensing region.
Claims17
A photoacoustic detector comprising:
- a sensing chamber;
- a source that directs radiant energy into the chamber;
- and
- first and second microphones with one oriented to detect acoustic activity in the chamber and with the other oriented to detect acoustic activity in a region different from the chamber.
1 more element
A photoacoustic detector comprising:
- a housing;
- a sensing chamber carried by the housing, the chamber has an input port which is covered by a gas permeable membrane;
- a source of radiant energy;
- an optical filter between the sensing chamber and the source configured to direct radiant energy into the chamber;
- a first microphone carried on the housing and configured to respond to acoustic events in the sensing chamber;
- a second microphone carried on the housing and covered by an acoustic filter, the second microphone is configured to respond to acoustic events outside of the sensing chamber;
- and
- control circuits coupled at least to the microphones, and responsive thereto, the control circuits form a difference signal between outputs of the microphones.
5 more elements
A method comprising:
- providing a sample of ambient atmosphere;
- directing modulated infra-red radiant energy into the sample;
- providing an acoustic output from the sample indicative of gas therein;
- providing another acoustic output from another sample;
- combining the acoustic outputs, and generating a difference signal without common mode noise;
- and
- generating a different signal indicative of the presence of gas in the sample.
4 more elements
Dependencies are inferred from the claim text.