Volume 9, Number 5 • September/October 2001 • Technology Transfer

Arizona Company Commercializes KSC Gauge

An Arizona company is commercializing the Force-Balanced Piston Gauge (FPG), originally designed for the NASA Kennedy Space Center (KSC) Metrology Laboratory to provide a Very Low-Pressure Primary Standard (VLPPS). Metrology deals with the science of weights and measures.

DH Instruments, Inc. (DHI) of Phoenix, a leading supplier of high-end calibration solutions for pressure and flow, is offering the FPG to industry for the first time, as an automated primary standard for very low-gauge and absolute pressures. DHI is currently making a limited commercial release of the FPG on a case-by-case basis to high-end metrology laboratories, according to Martin Girard, DHI’s chief executive officer.

Three systems have already been installed worldwide, including the Japanese National Research Laboratory for Metrology (NRLM) in Tsukuba, Japan; the National Measurement Institute (MIKES) in Helsinki, Finland; and Sandia National Laboratories in Albuquerque, New Mexico, the Department of Energy’s Primary Metrology Laboratory. DHI expects to deliver five more systems in a limited release phase and full commercial release to the general public in the summer of 2002.

Girard said that the origins of the FPG are in the recognition of the need for a primary pressure standard for both gauge and absolute pressures to cover the range under that covered by conventional piston gauges or deadweight testers (roughly 0 to 10 kilo pascals (kPa), and especially under 1 or 2 kPa). The first concepts for the product, based on the combination of a high-precision piston cylinder and a digital mass comparator, were developed in the late 1980s. In the early 1990s, in a NRLM and DHI joint effort, conceptual drawings were produced but not taken further until NASA requested calibration support for components of the International Space Station. DHI has been a supplier to the KSC Metrology Laboratory since the mid 1980s.

In late 1994, KSC expressed the need for an easy-to-use, low-pressure primary standard to support the calibration of instrumentation for the International Space Station. DHI provided an unsolicited proposal based on the work from the early 1990s. In July 1996, the proposal resulted in a contract to provide the FPG for use in the KSC Metrology Laboratory.

The KSC system was inspected and accepted for installation in August 2000. A major benefit of having the FPG at KSC means savings in time and money, since NASA no longer has to send components to the National Institute of Standards and Technology (NIST) for calibration. The innovation provides the lab with a traceable, primary calibration standard for measuring pressures in the ranges near absolute pressure (hard vacuum) or gauge pressure (atmospheric) within about one pound per square inch (psi) of either baseline. The hardware combines a large area piston-cylinder with a load cell measuring the force resulting from pressures across the piston. The mass of the piston can be tared out, allowing measurement to start from zero. A pressure higher than the measured pressure, which keeps the piston centered, lubricates an innovative conical gap located between the piston-cylinder. This eliminates the need for piston rotation. A pressure controller based on the control of low gas flow automates the pressure control.

The FPG is of great interest to a variety of industries, due to the critical nature of accurate measurements of very low absolute and gauge pressures, said Girard.

These include, but are not limited to, semiconductor manufacturing—measurement of residual pressure in process chambers; aerospace—measurement of very high altitude; and nuclear fuel processing—measurement of residual pressure in process chambers. Though calibration capability exists in this range, it is typically too expensive, too difficult to use and/or has uncertainties that are too high to satisfy the needs of industry.

DHI, founded in 1980 in Pennsylvania and now located in Phoenix, Arizona, has reached sales of more than $10 million in 2000. DHI’s customers include various types of organizations with high-end pressure and flow calibration needs, including aerospace, the military, semiconductor manufacturing, energy production, pharmaceutical, process control and national measurement institutes, like NIST. Q

For more information, contact Thomas Gould at Kennedy Space Center, 321/867-6238 or Thomas.Gould-1@ksc.nasa.gov Please mention you read about it in Innovation.

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