 | SOURCE The SOURCE button offers several triggering options depending on which view mode the instrument is set: • External: A TTL signal applied to the External Trigger MCX input connector causes a single sweep. After the sweep is complete, the resultant trace is continuously displayed until the next trigger signal is received. • Free Run: A new sweep is started immediately upon completion of the current sweep. No trigger event is required to initiate a sweep. • Video: Available only in zero span. A new sweep is started when the input video level meets the value set via the LEVEL button. Video triggering is useful for monitoring a known frequency and its time transients, such as pulsed signal rise or fall times. LEVEL Used in Zero Span mode when the trigger source is set to Video. Sets the video trigger level threshold that initiates a sweep. The level crossing applies to rising, falling, or both edges. Use the Hysteresis setting below to adjust the sensitivity of the trigger level. DELAY Used when the trigger source is set to External or Video. When set to On, the delay value sets the amount of time that the analyzer waits to begin a measurement after a trigger signal is received. For non-zero span, trigger delay can be set from 0 to 1670 ms. For zero span, trigger delay can be set from –(sweep time) to 1670 ms. Negative trigger delay effectively moves the trace to the right so you can observe the activity before the trigger event. HOLDOFF Used when the trigger source is set to External or Video. When set to On, the analyzer waits the user-defined amount of time to re-arm the trigger between trigger events. If a trigger event is received after the previous trigger, but before the holdoff time has elapsed, that trigger event will be ignored. PERIODIC Used to set a periodic sweep trigger. When set to On, the instrument waits the set time to start a sweep. The sweep trigger period can be set from 1 µs to 5 s. SLOPE Used when the trigger source is set to External or Video. Sets the trigger slope to rising, falling, or both. When slope is set to Both, the analyzer triggers on both the rising and falling edges. Triggering on both rising and falling edges is not available in Zero Span. HYSTERESIS Used to address noisy trigger signals. The hysteresis setting adjusts the sensitivity of the trigger system (the difference between the firing level and the arming level as shown in Figure: Trigger Levels and Hysteresis). A low hysteresis value sets the arming and firing levels close to each other, meaning a small signal change will cause a trigger. A large hysteresis value sets the arming and firing levels far apart, meaning a large signal change will be required to cause a trigger. |
