Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With coupling means
Reexamination Certificate
1999-05-04
2001-07-10
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With coupling means
C324S073100, C324S133000
Reexamination Certificate
active
06259246
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus and method for sensing a load and, more particularly, to an apparatus and method for deriving an indication of an electrically isolated load.
BACKGROUND OF THE INVENTION
Isolation amplifiers are commonly used for providing electric power to electrical equipment while isolating the electrical equipment from direct connection to a power source. Typically, an oscillating electrical signal is inductively coupled to electrical equipment, such as through a transformer, to provide electrical energy to the electrical equipment. A feedback connection may be provided from the electrical equipment to the power source to control the amount of electrical energy being provided through the transformer.
For example, U.S. Pat. No. 4,667,144 to Jones et al. discloses a high frequency, high voltage MOSFET isolation amplifier in which variations in the input signal are corrected by providing feedback through a magnetic yoke load circuit.
U.S. Pat. No. 5,187,446 to Daly discloses a feedback isolation amplifier that also employs a separate isolation amplifier as part of a feedback circuit to compensate for variations in the input and output signals.
U.S. Pat. No. 3,896,366 to Onogi discloses an isolation transformer having primary and secondary windings in which the current in each of the windings is controlled by a variable impedance element. The variable impedance element forms a current limiter under control of an input signal. This patent also discloses providing current or voltage feedback from isolated load equipment to an input of a differential amplifier at the primary winding to control the current conducted through the windings.
U.S. Pat. No. 4,506,230 to Ashley-Rollman discloses an isolation circuit formed of an isolation amplifier having a primary winding and a pair of secondary windings. One of secondary windings provides feedback to an operational amplifier on the primary side of the isolation amplifier circuit for compensation.
U.S. Pat. No. 4,541,040 to Allfather discloses a power conversion system in which an isolation transformer couples the output of a power amplifier to a load. An indication of the load is provided to the power amplifier through a separate feedback path.
SUMMARY OF THE INVENTION
The present invention is directed to a load sensing apparatus that includes a signal generator operative to provide a first oscillating signal to a first side of a coupling. The coupling also has a second side connected with an input load circuit and maintains electrical isolation between the signal generator and the input load circuit. The input load circuit receives a load signal having a value. A signal which varies as a function of the load signal is provided at the first side of the coupling.
Preferably, the coupling is a transformer through which information indicative of the value of the input load signal is transmitted to effect variations in electric current conducted through a primary winding of the transformer.
REFERENCES:
patent: 3602801 (1971-08-01), Williamson
patent: 3714540 (1973-01-01), Galloway
patent: 3793557 (1974-02-01), Cramer
patent: 3810012 (1974-05-01), Harris
patent: 3855101 (1974-12-01), Wilson
patent: 3896366 (1975-07-01), Onogi
patent: 4292595 (1981-09-01), Smith
patent: 4412184 (1983-10-01), Embree
patent: 4506230 (1985-03-01), Ashley-Rollman
patent: 4527118 (1985-07-01), Kosar
patent: 4541040 (1985-09-01), Allfather
patent: 4667144 (1987-05-01), Jones et al.
patent: 4769594 (1988-09-01), Darius et al.
patent: 4916329 (1990-04-01), Dang et al.
patent: 5187446 (1993-02-01), Daly
patent: 5392784 (1995-02-01), Gundaitis
Boyle Fredrickson Newholm Stein & Gratz S.C.
Eaton Corporation
Metjahic Safet
Sundaram T. R.
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