John C Ferrara

US Patent:

40115038, Mar 8, 1977

Filed:

Oct 16, 1975

Appl. No.:

5/622842

Inventors:

John M. Ferrara - Yardley PA

Assignee:

Narco Scientific Industries, Inc. - Fort Washington PA

International Classification:

H03D 1300
G01R 2500

US Classification:

324 83R

Abstract:

A known reference signal is applied to a zero crossing detector and normal and inverted outputs from the zero crossing detector are applied to the input control terminals of a pair of bilateral switches. A measured signal of the same frequency but not necessarily of the same phase is simultaneously applied to the input terminals of the bilateral switches. The resultant output of the bilateral switches is connected to a parallel RC network. The capacitor acquires a charge proportional to the deviation from 90. degree. , which is applied to a differential amplifier. The output of the differential amplifier is used to drive a meter which indicates the phase relationship of the two signals. The capacitor used to accumulate the net charge is ungrounded to eliminate errors resulting from unequal currents to ground.