Pressure transducer for monitoring a pneumatic tire

Abstract

A pressure transducer for use with a pneumatic tire monitoring system includes a non-conductor resilient layer and a piezo-resistive/variably conductive layer having a composition which provides substantially constant resistant while under a substantially constant load. In a preferred embodiment, the piezo-resistive/variably conductive layer includes N-type semiconductor material, molybdenum disulfide, titanium, bismuth oxide, and alkyd or silicone binder. The transducer also includes conductive elements which are attached to a nonconductive substraight and electrically insulated from each other. The piezo-resistive/conductive layer contacts at least two of the conductive elements with a surface area which is responsive to a change in pressure so as to produce a variable resistant/conductives between the conductive elements. In one embodiment, the piezo-resistive/conductive layer is hemispherically shaped and divided to produce two independent sensing transducers. The output of these transducers may be combined to improve the response linearity of the transducer. One embodiment utilizes a log/anti-log circuit and a differential amplifier to combine the output of the separate but integral transducers.