Monday, November 24, 2008

Microchip's new inductive touch-sensing technology

Microchip has a new line of touch sensing products called "inductive touch". Let me show their introduction rather than mine.

When a user presses the front panel, it deflects slightly. This deflection, on the order of microns, is inductively detected. The fundamental principle of operation is that the impedance of an inductor varies when a nearby magnetically permeable or electrically conductive material moves relative to the inductor.

Inductive Touch

As you shown from the above description and illustration, it's a kind of a pressure sensor while most capacitive touch sensors are categorized as contact sensors. It senses the change of distance between two parallel plates when a user presses down the sensor. In my opinion, the term touch now has three different meanings: contact, pressure, and proximity. There are many ways to construct a pressure sensor using various sensing techniques. The most popular but people are not aware is resistive touch screen. Capacitance sensing technique can also be used to pressure sensors (You can find an example in PPS web site).

Here, I have a question. The Microchip's document shows a comparison chart that compares inductive touch and capacitive touch. But I'd like to know differences between capacitive pressure sensing and inductive pressure sensing (inductive touch). There should be some differences, but I couldn't identify since I'm not so familiar with pressure sensing. Does anybody know an answer?

Comparison between inductive touch and capacitive touch

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