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:
Dec. 24, 1996
Filed:
Sep. 29, 1995
Robert P Rhodes, Lincoln University, PA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
A thermal conductivity detector includes a cavity wall defining a cavity for receiving a quantity of the sample fluid, the cavity wall being subject to a cavity wall temperature, and a sensor located in the cavity and connected as a first element in a bridge circuit configuration. The sensor exhibits a resistance which is dependent on a temperature of the sensor. A variable resistor having a selectable resistance in response to a control signal is connected in the bridge circuit configuration as a second element. A signal providing means, connected to the balance nodes of the bridge circuit configuration, provides a first signal which is related to a change in resistance of the sensor and thereby representative of the sensor temperature. Means for sensing the temperature of the cavity wall provides a temperature sense signal to a controller, which in response provides a heating control signal to a cavity wall heating means. The controller also determines the cavity wall temperature and in response causes the variable resistor to achieve a selected resistance value that will cause the sensor resistance to change. The temperature of the sensor is thereby set so as to accurately and reliably establish a selectable, predetermined temperature differential between the sensor and the cavity wall.