Delay generator DG645

Description

The DG645 is a versatile digital delay/pulse generator that provides precisely defined pulses at repetition rates up to 10 MHz. The instrument offers several improvements over older designs—lower jitter, higher accuracy, faster trigger rates, and more outputs. The DG645 also has Ethernet, GPIB and RS-232 interfaces for computer or network control of the instrument.

Delay Generator Timing

All digital delay generators measure time intervals by counting cycles of a fast clock (typically 100 MHz). Most digital delay generators also have short programmable analog delays to achieve time intervals with finer resolution than the clock period. Unfortunately, one clock cycle of timing indeterminacy (typically 10 ns) can occur if the trigger is not in phase with the clock.

The DG645 eliminates timing indeterminacy by measuring the timing of triggers with respect to the internal clock and compensating the analog delays. This approach reduces the jitter by about 100× and allows the internal rate generator to operate at any rate—not just a sub-multiple of the clock frequency.

Triggering

The DG645 has many trigger modes. An internal rate generator, with less than 100 ps period jitter, may be set from 100 µHz to 10 MHz with 1 µHz resolution. An external trigger input, with adjustable threshold and slope, can trigger a timing cycle, a burst of cycles, or a single shot. A single shot can be triggered with a key press. A line trigger operates synchronously with the AC mains. A rear-panel trigger inhibit input can disable the trigger or any of the pulse outputs during a timing cycle.