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:
Jan. 20, 2009
Filed:
Sep. 01, 2004
George Quinton Lyon, Peterborough, CA;
George Quinton Lyon, Peterborough, CA;
Siemens Milltronics Process Instruments, Inc., Peterborough, Ontario, CA;
Abstract
A protection circuit for a current loop powered level measurement or time of flight ranging apparatus. The protection circuit includes one or more Zener diodes, a leakage current detector circuit and a compensating current circuit. The leakage current detector circuit detects the leakage currents flowing from the Zener diodes and generates an output for the compensating current circuit. The compensating current circuit generates a compensating current so that the sum of the leakage currents and the compensating current remains a constant and the loop current is not affected by variations in the leakage currents for example as a result of variations in the voltage in the current loop or temperature of the device.