Fluke 8558A - Page 110

8588A/8558A
Operators Manual
106
Note
The Trigger layer, as well as the Arm2 and Arm1 layers, have Special Events not
shown in Figure 28, available through the SCPI remote commands. The Special
Events are described in Special Event Qualifiers.
The power-on default trigger event in the Arm2, Arm1, and Trigger layers is
Immediate, which provides automatic continuous triggering. With all three of
these layers set to Immediate, no other discrete trigger event is required to obtain
a reading as long as the Initiate layer is to Continuous ON. With the Initiate layer
set to Continuous OFF, the occurrence of any Event in any of the other layers
has no effect. The Trigger subsystem remains in the Idle state unless  is
pushed or the remoted command INIT:IMM is sent (described later).
The settable triggering events are:
• Immediate: No wait at the Event detector. This is the default state for all
layers and effectively allows the Product to take readings continuously in the
free-run mode. This is the power up default setting for all functions except for
Digitize and RF Power.
• External: Waits for a trigger edge input to the rear panel BNC connector. The
type and polarity of the edge is by default negative going TTL. Selection of
edge type is described below.
• Bus: Waits for a remote interface trigger command (*TRG or GET) from the
controlling computer
• Hold: Puts the Trigger subsystem in a suspended state, no readings are
taken. Hold pauses the Product from any signal acquisition until taken out of
that mode. Note that the “Hold” event is not related to “Holdoff” described
later.
• Internal: Waits for the input signal to reach a certain level on either the
positive or the negative going edge. Setting up the point (level) on the signal
is described below. Other digital multimeters may refer to this event
parameter as “LEVEL” or “ATrigger”.
• Line: The Event is satisfied synchronously with the line frequency. If the
acquisition time (the time it takes to complete a reading) is less than the
period of the line frequency, readings will occur at the line frequency. If the
acquisition times are longer than the period of the line frequency, readings
will be triggered at multiples of the line frequency period. For example, given
a long enough acquisition time, a 60 Hz line may result in triggering at 30 Hz
or 20 Hz.