Weston Instruments, Inc.

Austin T Kelly

A measuring device such as a digital thermometer uses dual slope analog-to-digital converter techniques but elminates the usual need for a high precision voltage source. An input capacitor is connected through novel switching to the temperature responsive arm and the temperature insensitive arm of a resistance bridge, to the low precision voltage source and to the output of the integrator and detector amplifiers. The switching sequence is such that long term changes in the voltage source and in the amplifier offset and drift are cancelled out during measurement cycles, thereby providing highly accurate measurements without the usual need for an expensive high precision voltage source.

Digital thermometer using a dual slope A/D converter without a high

A dual slope analog-to-digital converter, which has an autozeroing circuit for cancelling out integrator and detector offset and drift, is additionally provided with a circuit for injecting a voltage of selected polarity and magnitude to offset the input voltage of the converter such that the input voltage can be measured with respect to a nonzero reference line.

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Morristown, NJ, United States of America

Austin T Kelly