Data Translation DT300 Series, Руководство пользователя, Страница: 101 / 164

Principles of Operation
101
Figure 37 shows an example of performing a frequency measurement operation. In this
example, three events are counted during a duration of 300 ms. The frequency, then, is 10 Hz,
since 10 Hz = 3/(.3 s).
Figure 37: 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
disabled, 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 10 MHz. In rate generation mode, either the internal or external C/T clock input
source is appropriate depending on your application; refer to
page 95 for more information on
the C/T clock source.
Using 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 transitions
or low-to-high transitions), the duty cycle of the output pulses, and the gate type that enables
the operation. Refer to
page 97 for more information on the pulse output types; refer to page
96 for more information on gate types.
Ensure that the signals are wired appropriately. Figure 38 shows one example of connecting a
pulse output operation to the STP300 screw terminal panel using user counter 0. In this
example, a software gate type is used.
External C/T
Clock
Input Signal
frequency measurement
starts
frequency
measurement stops
Duration over which the
frequency is measured = 300 ms
3 Events Counted