John Fluke Mfg. Co., Inc.

Fluke Corporation

Jonathan J Parle

Todd E Holmdahl

Monte R Washburn

Steven D Swift

John M Lund

David Allen Gunderson

Martins Skele

A Brinkley Barr

A calibrated isothermal assembly for a thermocouple thermometer is provided to obviate a calibration step after manufacture of the instrument. A compact isothermal block is fabricated on a specialized printed circuit board which includes a thick metal plate to establish sufficient thermal mass and good heat conductivity. A temperature sensor is mounted at the thermocouple reference junction on the printed circuit board to track the reference junction temperature. The calibrated isothermal assembly also includes a current source for the temperature sensor, and a memory device containing stored calibration data specific to the temperature sensor.

Calibrated isothermal assembly for a thermocouple thermometer

A glitch trigger circuit for measuring glitches that appear on power line signals includes two comparators and two independently controllable voltage trigger levels to allow proper trigger on glitches of unknown polarity. A high pass filter rejects the power line signal while passing the glitch signals to provide triggering on glitches with voltage amplitudes less than the voltage amplitude of the power line signal.

Dual comparator trigger circuit for glitch capture

A charge-controlled integrating successive-approximation analog-to-digital converter first stores a charge proportional to an unknown voltage in a manner similar to a dual-slope integrating ADC, and thereafter a successive-approximation binary search sequence algorithm is applied to the integrator to determine digital bits representative of the unknown voltage. The result is a relatively simple and inexpensive ADC having high resolution and accuracy, and comparatively fast conversion rates, and exhibiting low power consumption, high noise rejection, and multiple-speed versatility. The preferred embodiment described is a 16-bit ADC with less than 20 millisecond conversion time.

Charge-controlled integrating successive-approximation analog-to-digital

A noise rejection circuit improves the signal-to-noise ratio of a ratiometric measurement circuit. A first operational amplifier produces a scaled-up voltage proportional to a low reference voltage. The scaled-up voltage is applied to a series connected reference resistance, whose value is known, and a resistance whose value is unknown and is to be measured. A parameter voltage formed across the resistance is applied to second operational amplifier acting as a buffer. A buffered parameter voltage is scaled down by a voltage divider. The scaled-down voltage is applied to a ratiometric converter, that produces an output representative of the unknown resistance value. The ratio of a first pair of resistors that determines the gain of the first operational amplifier is the same as the ratio of a second pair of resistors that form the voltage divider, such that the low reference voltage is scaled up and the parameter voltage is scaled down by the same factor. The ratiometric converter operates from a low power supply voltage and consumes low amounts of power. The first and second amplifiers are CMOS operational amplifiers that, despite operating from a relatively high power supply voltage, consume low amounts of power.

Ratiometric measurement circuit with improved noise rejection

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

Jonathan J Parle