Keithley KUSB-3100, User Manual

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Principles of Operation
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• Falling-edge external gate input – Enables a counter/timer
operation when a high-to-low transition is detected on the
Counter 0 Gate signal. In software, this is called a low-edge gate
type. Note that this gate type is used for edge-to-edge
measurement mode; refer to
page 30 for more information about
these modes.
• Rising-edge external gate input – Enables a counter/timer
operation when a low-to-high transition is detected on the
Counter 0 Gate signal. In software, this is called a high-edge gate
type. Note that this gate type is used for edge-to-edge
measurement operations; refer to
page 30 for more information
about these modes.
Pulse Duty Cycles
Counter/timer output signals from the KUSB-3100 module are
high-to-low going signals.
The duty cycle (or pulse width) indicates the percentage of the total
pulse output period that is active. In rate generation mode, the duty
cycle is fixed at 50% for the KUSB-3100 module.
Figure 4 illustrates a
high-to-low going output pulse with a duty cycle of 50%.
Figure 4: Example of a Pulse Output SIgnal with a 50% Duty Cycle
(High-to-Low Going)
Total Pulse Period
Active Pulse Width
low pulse
high pulse