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Section 7: Triggering
Source bypasses
As seen in the previous figure, each layer has a path that allows operation to loop around the control
source. Each path is called a source bypass.
When a source bypass is enabled, and the external or trigger link (triglink) control source is selected,
operation loops around the control source on the initial pass through the layer. If programmed for
another event detection in the layer, the bypass loop is in effect though it is still enabled. The bypass
loop resets (be in effect) if operation loops back to a higher layer (or idle).
In the arm layer and scan layer, enabling a source bypass also enables the respective output trigger.
In the trigger layer, its output trigger is always enabled and occurs after every device action. See
Output triggers
Delays
The scan layer and the measure layer have a programmable delay (0 to 999999.999 seconds) that is
enforced after an event detection.
Device action
The primary device action is a measurement. However, the device action could include a function
change and a channel scan (if scanner is enabled). A channel is scanned (closed) before a
measurement is made. When scanning internal channels, the previous channel opens and the next
channel closes (break-before-make). Also included in the device action is the internal settling time
delay for the relay.
Output triggers
In the arm layer and scan layer the output triggers are enabled only if their respective source
bypasses are also enabled. If a trigger link (triglink) control source is selected, the output trigger pulse
is available on the selected trigger link output line. In the measure layer, the output trigger is always
enabled and occurs after every device action. If the control source is set for external, immediate,
manual, GPIB or timer, the output trigger pulse is available at the trigger link connector. If the trigger
link (triglink) control source is selected, output trigger action occurs on the selected trigger link output
line as follows:
If the asynchronous trigger link mode is selected, the output trigger pulse is available on the
programmed output line.
If the semi-synchronous trigger link mode is selected and the source bypass is disabled, the
trigger link line is released (goes high).
If the semi-synchronous trigger link mode is selected and the source bypass is enabled, the
trigger link line is pulled down low and then released.
Counters
All three layers use programmable counters which allow operation to return to or stay in the
respective layer. For example, programming the measure layer counter for infinity keeps operation in
the measure layer. After each device action and subsequent output trigger, operation loops back to
the trigger layer control source. A counter resets when operation loops back to a higher layer (or idle).
7-8
(on page 7-8) for more information.
Model 6517B Electrometer Reference Manual
6517B-901-01 Rev. C / August 2015
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