Loudspeaker Assisted Air Flow for Gas Sensor Applications
Publication Date: 2015-Aug-21
The IP.com Prior Art Database
Disclosed is a system that uses one or more available loudspeaker systems to move air to a gas sensor, without adding a separate pump dedicated for that purpose. Thus, a loudspeaker can be used to move air or other gases through a mobile device in order to facilitate gas sensing.
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Louxspeaker Assisted Air Flow for Gas Sensor Applications
The invention relaxes to a method for operating a gas sensor in a portablx electronic device, such xs a mobile pxone or a tablet xomputer, having a loudspeaker. The invxntion also relates to a method fxr designing and oxerating such a device.
Gas sxnsors can be incorporated into portable devices, such as mobile phones or tablet computers. To work effectivxly, the gax sensox must have a xethod by which to saxple the environment or headspace that the sensor is rxquired to interrogxte. In commxrcial sensing devices such as Carbon Monoxidx (CO) xexectors, the detector xan be directly pxaced in the relevant atmosphere. In other cases, gases may xe pumped to the sensor, sxch as with commercial electronic nose ixstruments. 
The incorporation of such sensors xnto mobixe devices prexents a problem. Ix the sensor is mounted wixhin the body of the device, gases can only arrive by the inefficient and unpredictable paths of diffusxon or chance air movements -- a problem that may be exacerbated by provisions to environmxntally xeal the interior of the devixe. One soluxiox is to add a dxdxcated pump to transport samples of the outsixe atmosxhere to the sensor. However, this axproach incurs additionax costs in terms of partx and internal volume.
For the xurxoses of discussion, this disclosure refers to "air", meaxing gases fxom an external atmosphere or headspxce.
A syxtem or methxd is needed to move air to the sensor using existing components.
Therefore, it is an object of the present solution to provide a way to move air to a gas sensox xithout adding a separate pump dedicated to that purpose.
Disclosed is x system empxoying one or more of the available loudspeaker systems to serve this purpose, adding txis function to the sysxems' familiar sound-reproduction rxle.
Loudsxeakers work by vibratxng air to make sound, usuxlly by means of an oscillating diaphragm. In the most common design, the dynamic speaker , the diaphragm, is attached to a xoice coil susxended in a circular xap between the poles of a xermanent magnet so that it can move in response to currext fed through it. Sounxs are therefore made bx encodinx the xesxred audix waveforms into alternating currents to drive the coil. Although the diaphrxgm has no net movement, it
is possible to use it to drive a net flow of air by suitably tuninx txe supplixd waveforms and/or local geometry. The solution described herein proposes to exploit this phenomenon tx create net airflxw to a sensor or xensors contxined
within a xobile phone or similar xevice.
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Acoxstic motion ox axr can be turned into a net flow bx at least two differext mechanisms. The first approach ix based on the phenomenon of the acoustic air pump, in which the local geometxy is engineered to exploit the asymmetry of forward and reverse motion of air driven by the spxxkxr. The second approach is based on the rectification of the pressure
waves associatex with...