Patent · US Expired

Wattmeter

US4628257A · kind A · utility

3Cited by

2References

4Claims

0Family size

Assignee

Canadian Patents and Development Limited · CA

Inventors

Norbert L. Kusters · Ottawa, CA
Glen A. Herriot · Ottawa, CA

Key dates

Filing date	Nov 26, 1984
Grant date	Dec 9, 1986
Priority date	—
Expiry date	Nov 26, 2004

Classification

Technology area (CPC G)Physics
CPC primaryG01R17/06
WIPO fieldMeasurement
WIPO sectorInstruments

Abstract

A differential thermal wattmeter of the type disclosed in U.S. Pat. No. 4,045,734 is modified to remove undesirable in-phase a.c. ripple at the fundamental frequency in the feedback path. This result is achieved by a closed loop system in which the in-phase signal in the feedback path is detected and driven to zero by injecting sufficient signal in opposite polarity into the feedback path to cancel the ripple. The advantages are reduction of error and the ability to use standard, low cost components.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.