Digital converter apparatus for improving the output of a two-wi

Details Digital converter apparatus for improving the output of a two-wi Digital converter apparatus for improving the output of a two-wi

1988-04-28

1993-02-16

Oberley, Alvin E.

Communications: electrical

Continuously variable indicating

Using a particular modulation

34087037, G08C 1916, G08C 1910

Patent

active

051874741

ABSTRACT:
An existing analog two-wire transmitter has a sensor module, an analog excitation circuit, and an analog detector circuit which provides an output representative of a sensed process variable, such as pressure, to a two-wire current loop. The analog detection circuit is removed and replaced with apparatus including a digital converter that digitally calculates the transmitter's output. The output is improved by calculating correction for linearity. The analog excitation circuit may also be replaced with a replacement excitation circuit. The replacement excitation circuit and the digital converter can be energized in series to control energization current. A charge pump can be coupled to the loop to balance the current in the series circuit. The digital converter can also provide electrical span and zero adjustments.

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"Rosemount Inc.'s Instruction Manual for the Model 1151DP Alphaline.RTM. Differential and High Differential Pressure Transmitters," Model 1151DP/HiDP, FIGS. 4--4, 4-7, pp. 4-10, 4-15.

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