The Xsensor pressure pad system from Sensor Products Inc. (East Hanover, NJ) is an electronic tactile force and pressure-indicating sensor that can monitor in real time how force is dispersed between any two contacting or mating surfaces. It can capture pressure ranges from 0.1 to 12,000 psi. Its uses include measuring pressure distribution between components of machine assemblies such as gaskets and flanges, clutches and brake plates, frames, shafts, welding heads or gear teeth. Other applications range from the determination of effective placement of strain gauges to measuring forces in automotive crash tests.
The lightweight pad that is the heart of the system is 11 mils (0.28 millimeter) thick and has sensing points inside it that can capture up to 60,000 sensing points per second. Up to four pads can be used to map applications simultaneously. In addition, the unit can record and interpret contact force in real time.
"The basis of the technology is capacitance," says Andrea LoMonaco, Xsensor product manager. "We have a patent for our Xsensor system that eliminates the major problem of capacitance, which is neighboring sensor cell causing feedback and interference (to surrounding cells)."
Depending on the resolution desired, the sensing points can be spaced at any increment from 1 millimeter on up and that is expected to drop to 0.5 millimeter in future versions. LoMonaco says that the resolution will affect the frame rate, or the rate at which successive pressure images can be delivered. "A larger pad with high resolution will increase the number of sensing points, thus decreasing the frame rate. If you are testing a static application, the frame rate is less important than an impact study for crash testing where 50 to 100 Hz would be necessary to gather the data."
The cost of the system begins at about $15,000 depending on the individual specifications and resolution, LoMonaco says. For instance, the unit developed to measure seating systems cost $14,500 because it doesn't require as high a resolution as other applications.
"It is wise to have this option because there are many applications that do not necessitate high resolution. Our seating sensor has approximately 8 millimeters spacing. On the other hand, you would need high resolution for applications such as tire tread, most biomechanical applications and gasketing."
The skin itself is available in a minimum pad size of 1 by 1 inch and is customizable up to a maximum pad size of 32 by 80 inches. The system is made to resist harsh environments, according to product literature, including temperatures up to 165 F and can be used several hundred times before it needs to be replaced.
The flexible system works on curved surfaces, which allows applications in windshields, door seals or impact studies in which the pad is affixed to the test dummy or along the dashboard. "The system will test pressure between any two contacting or mating surfaces, regardless of the shape," LoMonaco says.
The data can be collected and the mapped images can be displayed in 2-D, 3-D or histogrammic formats for dynamic measurement. The system has the ability to display the average pressure over a specific time interval from each sensor cell. Numerical data and text comments can be printed in either color or black and white. The data can be displayed in variable viewpoints and Xsensor allows rotation of the data in 90-degree increments for the most intuitive orientation.
A system consists of a pressure-mapping pad, a data collection controller, interface hub, power supply, interface cables and software. To use it, a minimum of a 266 MHz Pentium computer or laptop with a serial port, Windows 95/98/2000/XP and 64MB RAM.
For more information on the Xsensor, contact:
Sensor Products Inc.
188 Rt. 10
East Hanover, NJ 07936-2108
Fax: (973) 884-1699