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:
Mar. 15, 1994
Filed:
Feb. 18, 1993
David K Davies, Churchill Borough, PA (US);
Thermo King Corporation, Minneapolis, MN (US);
Abstract
A system for compensating for changes in pressure and temperature in an ion mobility sensor has first and second electrodes positioned a selected distance apart, with a unidirectional electric drift field provided between the electrodes. An ionization source generates ions in the sensor and a trigger controller allows ions to enter the region between the first and second electrodes at a time t.sub.1. A time t.sub.2 at which a selected ion species travels to one of the first and second electrodes is measured and a time to amplitude converter generates a voltage signal proportional to the difference between t.sub.1 and t.sub.2, representing the actual travel time of the ion species. A feedback control circuit adjusts the drift field and either the voltage pulse (in pulsed ionization) or the shutter voltage (in continuous ionization) by an amount proportional to the difference between the actual travel time voltage and a voltage proportional to a reference travel time of the selected ion species at a known pressure and temperature.