Colin L Shepard

US Patent:

20030160625, Aug 28, 2003

Filed:

Feb 11, 2003

Appl. No.:

10/365202

Inventors:

A. Kaufman - Beaverton OR, US
Roland Andrews - Sequim WA, US
Colin Shepard - Hillsboro OR, US
William Mark - Hillsboro OR, US
Lester Larson - Portland OR, US
Donald Murray - Beaverton OR, US

International Classification:

G01R031/28

US Classification:

324/754000

Abstract:

An instrument includes a probe providing a single signal path for conveying a signal from a circuit under test to the instrument. A receiver circuit within the instrument divides the path into an analog path and a digital path. The digital path includes a comparator for determining the logic state of the signal and producing a digital representation of the signal under test. The analog path includes a multiplexer to selectively couple one of a plurality of analog input signals to an output terminal for viewing on an oscilloscope. Preferably, the probe head includes a buffer amplifier to reduce loading on the circuit under test and to increase bandwidth of the signals conveyed along the test cable to the instrument. An electrically trimmable resistor is employed to terminate the transmission line of the test cable in its characteristic impedance in order to reduce reflections and maintain transmission bandwidth.