Fluke Corporation

John Fluke Mfg. Co., Inc.

Eldec Corporation

Steven D Swift

Greg Gibson

Jonathan J Parle

John M Lund

David Allen Gunderson

Roger E Baker

Erik R Little

An rms converter accommodates incoming signals of large crest factor by using an amplifier having a transfer function of non-uniform slope. The amplifier has a lower gain for larger signals. The output of the amplifier is converted to digital voltage values. The non-uniform gain of the amplifier is compensated for in digital calculations of the rms value. The invention produces accurate rms measurements by accurately measuring lower incoming signal voltages while still accommodating high peak voltages. The invention also reduces the dynamic range requirements for the analog to digital converter.

High crest factor rms measurement method

A front-end architecture is provided for a measurement instrument having a single path for the input signal for conversion into digital samples. A signal conditioner may be coupled via a pair of test leads across a voltage source, current source, or component to develop an input signal. The input signal is provided to a sampling system, which comprises a sigma-delta converter followed by a decimation filter, which over-samples the input signal to produce a continuous stream of digital samples. The digital samples are provided to a set of digital extraction filters, each digital extraction filter having a structure and transfer function adapted for extracting a measurement parameter from the stream of digital samples. Parameter extraction is performed on a continuous basis so that the digital samples and the resulting digital measurement values arrive in a continuous stream. Extracted parameters include the d.c. value of the input signal, the rms value of the input signal, the waveform parameters of the input signal, and the peak min/max values of the input signal.

Front-end architecture for a measurement instrument

A circuit for measuring alternating current (a.c.) and direct current (d.c.) in a conductor without breaking the conductor is provided. A modulated current source is coupled in parallel with a segment of the conductor to inject a test current. A synchronous demodulator is also coupled in parallel across the segment to separate the test voltage drop induced by the test current from the voltage drop due to the current in the conductor. The test voltage drop and the voltage drop are measured by a voltmeter and the resistance of the segment and the current flowing through the segment can then be calculated.

Circuit for measuring in-circuit resistance and current

An adaptive digital filter is provided to obtain improved measurement accuracy in an electronic instrument which has a front-end circuit for coupling to an input signal to be measured. An analog to digital converter converts the input signal received through the front-end circuit into a stream of measurement values during the measurement phase. The stream of measurement values are then provided to the adaptive digital filter which mathematically operates on them to remove the frequency response effects of the front-end circuit in a process of convolution in the time domain using a set of digital filter values obtained during the calibration phase. Because the frequency response requirements of the front-end circuit have been eased with the addition of the adaptive digital filter, a simpler front-end circuit with fewer components and with no need for manual adjustment may be employed in electronic instruments.

Adaptive digital filter for improved measurement accuracy in an

An improved open circuit detector for testing a thermocouple for an open circuit condition. The detector includes a generator for providing and sourcing a tone signal to the thermocouple, wherein the tone signal has a known frequency and amplitude. A monitor analyzes the amplitude of a particular frequency component of a tone signal across the thermocouple. If the amplitude of the particular frequency component exceeds a predetermined threshold, an output is provided for indicating an open circuit condition for the thermocouple.

Thermocouple open circuit detection with tone frequency signal

A power supply system for controlling the drive voltages applied to a thin film electroluminescent (TFEL) display panel is disclosed. The system includes a power supply that generates the drive voltages to the TFEL display panel and causes it to emit light. A replaceable or resettable display voltage memory located adjacent the display panel provides the power supply with voltage information specific to the display panel. A feedback circuit measures the light emitted from the display panel. A balancing circuit controls multiple display voltages so that they have the proper relationship with respect to each other. The information from the display voltage memory and the feedback circuit is used by the power supply to control the output of the display voltages.

Thin-film electroluminescent display power supply system for providing

Bi-polar electronic signal converters, such as analog-to-digital or digital-to-analog converters, with a single polarity accurate reference source are disclosed. In one polarity direction, the accurate reference source is used in a conventional manner to transform the signal to be converted from one form (e.g., analog) to the other form (e.g., digital). In the other polarity direction, an inaccurate reference source is used in a similar conventional manner to convert the signal from one form to the other form. Periodically, the accurate and the inaccurate reference sources are compared to determine a correction multiplier. The correction multiplier is used during conversions using the inaccurate reference source to compensate for the inaccuracy of the inaccurate reference source.

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Seattle, WA, United States of America

Steven D Swift