Measurement Computing Data Translation DT3034, User Manual

Page: 104 / 178

Principles of Operation
103
Figure 33 shows an example of 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 33: 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,
analog output, or other counter/timer operations.
While the pulse output operation is enabled, 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 the external clock
divider. If you are using one counter (not cascaded), you can output pulses using a maximum
frequency of 10 MHz (this is the frequency of the clock output signal). In rate generation
mode, either the internal or external C/T clock input source is appropriate depending on your
application; refer to
page 96 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 99 for more information on pulse output signals and to page 98
for more information on gate types.
Ensure that the signals are wired appropriately. Figure 34 shows one example of connecting a
pulse output operation. This example uses the DT740 screw terminal panel, user counter 0,
and a software gate type.
External C/T
Clock
Input Signal
frequency measurement
starts
frequency
measurement stops
Duration over which the
frequency is measured = 300 ms
3 Events Counted