Hewlett-packard Company

Agilent Technologies, Inc.

Michael L Beyers

Matthew S Holcomb

John Angus Foster

A digital oscilloscope automatically selects as the initial instance of a waveform parameter to be measured the instance that is both visible in the displayed trace and closest to the trigger reference point. Such a manner of automatic selection allows a greater amount of panning and zooming while the 'scope is subsequently stopped, without causing a different instance to become the measured instance, and also reduces confusion about continuity of measurement while the display is altered with the 'scope is still running. This automatically selected choice can still be overridden, if desired, by a manual selection. A further refinement is to, once an instance is automatically selected, retain it as the selected instance as long as it remains visible as part of a modified displayed trace, even if it would not otherwise become the selected initial instance if the measurement activity were first initiated with that modified trace. Still another refinement is to alert the operator that, owing to the previously automatically selected instance having been panned or zoomed off screen, a new and different automatically selected instance is now being measured.

Digital oscilloscope's automated parameter measurement cooperates with

Each acquisition record in a random repetitive oscilloscope is time stamped and stored in a location in the acquisition memory indexed by the associated value of trigger offset. Those acquisition records that are older than a selected and variable amount can be discarded instead of being used to contribute data to the waveform record. This has the effect of preventing old data from intruding into a new measurement. When reformulating the waveform record to pan or zoom while using data already acquired, it is possible to ensure that the newest waveform records are included in that reformulation. This has the effect of ensuring that new data is displayed. The time stamp may be a binary count of an elapsed time interval, in units of the sample clock, since some cardinal event, such as the last time ERASE or RESET was pressed. To maximize the random distribution of the trigger offsets represented in the acquisition memory, the rule for deciding which of m-many acquisition records receives this latest data is based on the trigger offset. The first of the acquisition records gets acquisitions whose trigger offsets are at least zero but less than 1/m of a sample period t, the second receives acquisitions whose trigger offsets are at least t/m but less than 2 t/m, and so on.

Digital oscilloscope with pan and zoom produced from time stamped data

A method, and circuit for implementing the method, allow a deep memory digital oscilloscope or logic analyzer to rapidly display large data records. Incoming signals are 'dually' processed through multiple data compression circuits so as to create and store at least two data records. A smaller record is available for immediate and rapid display. A larger record is available for subsequent panning & zooming. By storing sequential data records in alternating memory divisions and eliminating data moves, the larger record may also be viewed more rapidly.

Method of rapidly displaying large data records retrieved by deep memory

In a test instrument, display locking is reduced by the addition of a non-constant time delay to each acquisition cycle. The time delay may be randomly chosen or follow a predetermined algorithm. Decreased system throughput caused by the addition of a non-constant time delay may be minimized by alternately storing acquired data in two acquisition memories. Display locking may also be reduced by rejecting selected triggers. The data acquired from these selected triggers is not processed for display. The triggers whose data is not processed for display may be randomly chosen or they may be chosen by a predetermined algorithm. Rejecting triggers and the addition of a non-constant time delay may be used in combination or individually to reduce display locking.

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Colorado Springs, CO, United States of America

Michael L Beyers