Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

A Capacitive Probe for Measuring the Clearance Between the Piston and the Cylinder of a Gas Piston Gauge



Walter J. Bowers Jr., Douglas A. Olson


We propose a method of determining the radial clearance between the piston and cylinder of a gas piston gauge using a capacitive technique. This method allows a determination of the effective area of a piston gauge pressure standard, independent of calibration against another piston gauge or manometer, as long as the piston diameter is dimensionally measured. It also allows an independent determination of piston gauge distortion due to pressure. We have used this technique to measure the clearance and the distortion of six gas piston gauges of the Ruska 2465 type operating in gauge mode. Measurements were made on two gauges each in the low, middle, and high ranges. In this paper we describe the capacitance technique and the results of the measurements on the six piston gauges.
Review of Scientific Instruments


capacitance, effective area, gas piston gauge, piston gauge distortion, pressure standard
Created March 10, 2010, Updated February 19, 2017