Bnc 645 User Manual download pdf (Page 56)

signal is a TTL “high” at the beginning of the sweep and turns to “low” at

the marker frequency. For sweeps with Marker Off

, the Sync signal is a

square waveform with a 50% duty cycle. That is, the Sync signal is a TTL

“high” at the beginning of a sweep and turns to “low” at the midpoint of

the sweep. The frequency of the Sync signal is the reciprocal of the

specified sweep time.

The default marker frequency is 500 Hz. The range of the marker

frequency is depending on stop frequency setting or frequency span

setting. The marker frequency must be less than or equal to the

maximum output frequency.

Trigger Source

The waveform generator outputs a single sweep when it receives a

trigger signal, and it keeps outputting the same type of waveform with

the start frequency before it receives next trigger and sends out another

sweep.

Trigger Source can be internal, external or manual, and the default is

Internal.

•

With internal trigger source, the waveform generator continuously

outputs sweeps with the specified sweep time.

•

With external trigger source, the trigger signal is a TTL pulse with

specified polarity applied to the

Ext Trig connector on the rear

panel. Note that the trigger period must not be less than 1 ms plus

the specified sweep time.

•

If manual trigger is selected, the waveform generator sends out a

sweep each time the Trigger button on the front panel is pressed.

Trigger out Signal

A “trigger out” signal is provided on the rear panel Ext Trig / FSK / Burst

connector. When enabled, a TTL-compatible square waveform with

either a rising or falling edge is outputted at the

Ext Trig / FSK / Burst

connector with the sweep output.

•

With internal trigger source, a square waveform with 50% duty

cycle is outputted at the Trig Out connector with the sweep

output.

•

With external trigger source, there is no signal outputted at the

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Bnc 645 User Manual Page 56