The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 05, 2002
Filed:
May. 10, 2000
Norbert Rolff, Horrem, DE;
Rudolf Stocker, Azmoos, CH;
Unakis Balzers AG, Furstentum Liechtenstein, US;
Abstract
Two resistance elements ( ) are used for eliminating the influence of wall temperature on the gas pressure in a vessel, determined by a Pirani manometer. The first resistance element ( ) is present in a first branch of a Wheatstone bridge ( ), and the voltage is tapped by means of a voltage divider ( ). The second resistance element ( ) is present with a series resistance ( ) in the second branch and is adjusted to a lower temperature. The changes in the voltages tapped at the branches are essentially identical for identical temperature changes at the resistance elements ( ), so that the Wheatstone bridge ( ) remains balanced. The adjustment is improved by a constant current source ( ). Another embodiment uses only one resistance element, whose temperature is reduced periodically during the balancing of the Wheatstone bridge and, after thermal equilibrium has been established, is determined by determining its resistance by means of a low constant current and is used for the computational compensation of the effect of the wall temperature. In a further embodiment, transient effects are produced by periodically switching a resistance back and forth and the frequencies are measured, from which the gas pressure is then determined.