Accession Number:

AD0689157

Title:

THE APPLICATION OF THE DIRECT CURRENT COMPARATOR TO A SEVEN-DECADE POTENTIOMETER,

Descriptive Note:

Corporate Author:

NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO) RADIO AND ELECTRICAL ENGINEERING DIV

Report Date:

1968-06-17

Pagination or Media Count:

6.0

Abstract:

The design and construction of a self-balancing direct current comparator for use in a seven-decade potentiometer is described. The comparator generates an output current whose value, as a proportion of a constant input current, is determined to a very high accuracy by the ratio of the numbers of turns of two windings on a magnetic core. A linear, adjustable voltage scale is obtained by passing this output current through a resistor whose value does not vary with current. Since the voltage adjustment is made by varying turns on a magnetic core and not by means of a resistive divider, the usual problems of contact resistance and thermal electromotive forces associated with this adjustment in conventional potentiometers are avoided. The main sources of error in the comparator and the design techniques used to keep the errors less than the smallest step of the output current are discussed. A self-checking feature whereby the linearity of each step of the output current can be checked quickly and easily is described. The performance of the prototype model is given. The normal range of the potentiometer is from zero to 2 volts in steps of 0.1 microvolts. Author

Subject Categories:

  • Test Facilities, Equipment and Methods

Distribution Statement:

APPROVED FOR PUBLIC RELEASE