Walter Joseph Ross

US Patent:

48499030, Jul 18, 1989

Filed:

Jul 15, 1987

Appl. No.:

7/073541

Inventors:

James C. Fletcher - Washington DC
Walter L. Ross - Simi Valley CA

Assignee:

The United States of America as represented by the Administrator of the
National Aeronautics and Space Administration - Washington DC

International Classification:

G01N 2704
G05B 2402

US Classification:

364482

Abstract:

A digitally controlled resistance generator (10) in which resistors (16-38) having values selected according to an expression 2. sup. N-1 (R), where N is equal to the number of terms in the expression, and R is equal to the lowest value of resistance, are electrically inserted into a resistive circuit in accordance with a parallel binary signal provided by an analog-to-digital converter (46) or a programmable computer (75). This binary signal is coupled via optical isolators (50-72) which, when activated by a logical "1," provides a negative potential to some or all of the gate inputs (96) of the normally "on" field effect transistors (98-120) which, when "on," shorts out the associated resistor. This applied negative potential turns the field effect transistors "off" and electrically inserts the resistor coupled between the source terminal (124) and the drain terminal (122) of that field effect transistor into the resistive circuit between the terminals (12, 14).