Method and apparatus for AC signal comparison, calibration and measurement
AssigneeElectro Scientific Industries, Inc.
InventorsArchie J. Harrison, Jr., Fred L. Katzmann
Life of this patent
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Abstract
A method and apparatus for the comparision of AC signals by electrothermal means in which both signals are applied to an electrothermal converter, such as a thermocouple converter or a thermoresistive converter, and the temperature produced by the signals is converted to a difference signal. The DC component of the difference signal is used to maintain the electrothermal converter at a stable operating temperature. The AC component of the difference signal is used to indicate the difference between two signals when used as a comparator, to control the amplitude of a reference standard's output when used as a voltmeter or calibration standard, and also to control the amplitude of an oscillator when used as a calibration standard.
Claims11
Electrothermal conversion apparatus for generating a DC voltage related to the RMS value of an AC signal comprising:
- (a) first elongate means for generating thermal energy in response to a first signal;
- (b) second elongate means for generating thermal energy in response to a second signal;
- (c) said first and second means being in physical contact with one another over a substantial portion of their lengths, separated only by thermally conductive electrical insulation over the substantial portion of their lengths for which they are in physical contact, and forming a heater assembly;
- and
- (d) a temperature responsive electrical sensing means in physical contact with said heater assembly, said temperature responsive means producing a temperature-indicating electrical signal representative of the temperature of said heater assembly.
Electrothermal conversion apparatus for generating a DC voltage related to the RMS value of an AC signal, comprising:
- (a) first means having a length for generating thermal energy in response to an AC signal;
- (b) second means having a length for generating thermal energy in response to a reference signal, the first and second means being twisted together over a portion of their lengths and being in thermal contact;
- and
- (c) a temperature responsive electrical sensing means in thermal contact with both the first and second means for producing thermal energy, the temperature responsive means producing a temperature-indicating electrical signal representative of the temperature produced by the first and second means.
Dependencies are inferred from the claim text.