Keithley KPCI-3101 Series, Руководство пользователя

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2-26 Principles of Operation KPCI-3101 — KPCI-3104 Series User’s Manual
Figure 2-14 shows an example of performing a frequency measurement operation. In this exam-
ple, three events are counted during a duration of 300ms. The frequency, then, is 10Hz, since
10Hz = 3/(.3 s).
Figure 2-14
Example of frequency measurement
Rate generation
Use rate generation mode to generate a continuous pulse output signal from the counter; this
mode is sometimes referred to as continuous pulse output or pulse train output. You can use this
pulse output signal as an external clock to pace other operations, such as analog input or other
counter/timer operations.
While the pulse output operation is enabled (determined by the gate input signal), the counter
outputs a pulse of the specified type and frequency continuously. As soon as the operation is dis-
abled, rate generation stops.
The period of the output pulse is determined by the clock input signal and external clock divider.
If you are using one counter (not cascaded), you can output pulses using a maximum frequency
of 10MHz. In rate generation mode, either the internal or external C/T clock input source is
appropriate depending on your application; refer to
page 2-19 for more information on the C/T
clock source.
Using DriverLINX software, specify the counter/timer mode as rate generation (rate), the C/T
clock source as either internal or external, the polarity of the output pulses (high-to-low transi-
tions or low-to-high transitions), the duty cycle of the output pulses, and the gate type that
enables the operation. Refer to
page 2-22 for more information on the pulse output types; refer
to page 2-21 for more information on gate types.
External C/T
Clock
Input Signal
Frequency Measurement
Starts
Frequency Measurement
Stops
Duration over which the
frequency is measured = 300ms
3 Events Counted