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Closed Loop Digital To Analog Conversion

IP.com Disclosure Number: IPCOM000089561D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Dannenberg, RE: AUTHOR

Abstract

A closed loop digital-to-analog conversion is accomplished without the use of expensive precision components.

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Closed Loop Digital To Analog Conversion

A closed loop digital-to-analog conversion is accomplished without the use of expensive precision components.

The main control 10 provides a three-digit digital-to-analog conversion which is scaled down to the required voltage by resistors R1 and R2 to establish a reference for the control amplifier 12. Regulation is achieved by comparing the feedback voltage from R shunt to the reference voltage developed at the junction of R1 and R2, in the control amplifier 12. The digital meter 14 is used to read and display the voltage developed across R shunt. Although regulation is achieved at the control amplifier 12, all preceding components including the control amplifier contribute to error and thermal drift. Usually, this error is eliminated by using precision and temperature-compensated components which are very expensive.

The loop can be inexpensively closed by comparing the digital output from the panel meter 14 with the desired digital value by means of a digital comparator
16. The comparator 16 controls the direction of an up/down counter 18, which is incremented by each step command from the meter 14. The binary count output of up/down counter 18 is applied to a binary digital-to-analog converter which converts the binary count to an analog correction voltage which "tunes" the reference voltage at the junction of R1 and R2. The addition of the digital comparator 16, the binary up/down counter 18 and the 12-bit binary digi...