|
Inexpensive and Integrable Pressure Sensor Material
Available in wire or composite material form or can be incorporated into a chip.
Introduction
Most electrical analog sensors concentrate on high accuracy, and therefore are expensive. In addition, many electrical analog pressure sensors are physically sensitive devices that must be protected and in many cases treated very carefully. We have developed a rugged prototype of a material that is inexpensive and demonstrates measurable reactions to changes in pressure that can be measured and used as pressure sensor. The material can be made more/less sensitive to pressure and more/less sensitive to temperature. Furthermore, this material is available as a low-cost double conductor wire that can be easily incorporated (with or without an imbedded system) into an application at a low cost. It is a simple transducer based solution.
Identification of Innovation and Application
A simple example of a pressure measurement system is one used for flushing a household toilet. A buoyant ball is placed in the toilet tank. The ball is attached to the water valve via a rod. As the water level rises, the ball is forced upward by the displacement of water. The rod transfers the pressure that results to the water valve, turning the valve off. This is an example of a mechanical analog pressure-based water level system. A similar type of pressure measurement system is a water pressure sensor. In this case, a diaphragm actuates a lever, which displays analog pressure via a gauge. To create an electrical output from the water pressure sensor, several different techniques are typically used. The lever is attached to a variable resistor, or a LVDT (Linear Variable Displacement Transducer), a strain gauge, or other device. Other techniques use a pressure sensitive material that demonstrates changes in resistance when squeezed by a diaphragm. The resistance change can be electrically measured and the pressure, or temperature, can be calculated. Today, companies offering pressure-sensing technology use these techniques.
Our approach is to use existing, well developed, coaxial cable manufacturing techniques to produce a polymer based, electrical resistance testing, inexpensive, pressure sensor from the pressure sensitive material that we have already, in a rugged form, invented and tested. A cross-section of the proposed coaxial cable is shown in Figure 1.
The thickness is variable, as are the pressure to resistance properties. But, the overall diameter is less than the thickness of a dime. The coaxial cable pressure sensor has other unique properties. It is one of the only pressure sensors that has a built-in integrity check. By applying sensing currents to the inner and outer conductors, it is possible to tell if the sensor is intact or if it is damaged. This feature alone makes this pressure sensor ideal for safety related systems. Based on our current projections, including manufacturing, marketing, and overhead costs, initial retail costs for such a pressure sensitive cable would be far less expensive than other pressure sensors.
One such application, using the manufactured pressure sensitive cable is an imbedded pressure/weight sensing device for industrial work gloves. With the embedded technology, the gloves will warn an individual by sounding a tone when they are lifting more than a configurable number of pounds. Since the innovation is accurate and cheap, the cost of the gloves would increase minimally.
Figure 2 gives an example of a type 40 Impress wire and resistance as a function of force or pressure and wire length.
Back to Impress Main Page /
Impress Applications /
Impress Exclusive Rights |
|
