John R. Potts, Senior Scientist/Engineering Manager

BRIEF

The instrument described in this paper has not yet been released for sale. It will be available for sale during the first quarter of 2006.
tparty™ Pressure Analyzer 2.0 is a PC-based instrument which employs multiple solid state pressure transducers connected to bladder detectors via transmission tubing, and automatically digitizes, converts, and displays their voltage analogs of pressure, all under Microsoft® Excel. tparty™ Pressure Analyzer 2.0 is installed and run as a COM Add-in under Excel, which greatly extends the functionality of the instrument. Third-Party R&D has successfully used this software approach for a number of other commercial instruments it markets as well, because it offers intimate integration with the familiar standard Windows program, Microsoft® Excel. This integration results in a convenient, powerful PC-Based Tool capable of acquiring and/or analyzing performance data for characterizations and/or diagnostic evaluations for a wide variety of industrial applications, including tight-fitting clothing apparel. A bladder pressure detector and small diameter plastic transmission tubing connect to each solid state pressure transducer and permit accurate measurements over relatively long distances between a solid state transducer and bladder. This paper discusses a simple performance model for pressure measurement systems, consisting of a bladder pressure detector, connecting tubing, transmission tubing, and solid state pressure transducer. An Excel file may be downloaded from this website, based on the simple bladder detection model, which allows one to modify tubing diameters and lengths and estimate detector performance characteristics and pressure measurement limits.

BLADDER PERFORMANCE MODEL

The figure above shows that all tubing (i.e., gage and bladder nipples, coupling tubing, and transmission tubing) are considered in the simple model, since their respective volumes are generally significant and act to limit the range of pressure measurements which are accessible. The gage transducer is solid-state and has a rigid plastic nipple with dimensions nominally 0.105 inch OD, 0.05 inch ID, and length 0.315 inch. As a point of interest, the OD tapers 2 degrees from top to bottom, however, the ID appears constant. The transmission tubing and coupling tubing are generally made of Tygon®, a proprietary class of materials and formulations developed specifically for fluid transport tubing (somewhat similar to vinyl tubing), and is a registered trademark of Saint-Gobain Performance Plastics. The cross-sectional dimensions for the transmission tubing are nominally 0.031inch ID and 0.093 inch OD. The cross-sectional dimensions for the coupling tubing are nominally 0.093 inch ID and 0.153 inch OD. The tubing is quite flexible, however, it is reasonable to assume that the ID does not vary over any length under normal use, and so for practical purposes can be considered a rigid material. The rigid tubes are assumed to simply connect bladders to linear, highly reproducible, fast, and accurate pressure sensors. In practice, the distance between a bladder and solid state pressure sensor generally varies from inches to several feet.

BLADDER MATERIALS

Specific bladder material properties are not included in the simple performance model and will not be discussed in detail. The following general comments relate to pressure measurements between tight-fitting clothing apparel and skin. The material selected for the bladder pressure detector in direct or indirect contact with skin is generally highly elastic and relatively soft (low durometer reading). Neoprene bladders are highly elastic, soft, can be made relatively thin (0.030 inch thick bladder wall), and reportedly do not cause the skin irritation attributed to natural rubber. A typical small bladder used for the tparty™ Pressure Analyzer has a nominal volume, Vb, of about 0.6 cm3.