Measurement Computing Data Translation DT3010 Series, Руководство пользователя, Страница: 138 / 232

Principles of Operation
137
Frequency Measurement
Use frequency measurement mode to measure the frequency of the signal from counter’s
associated clock input source over a specified duration. In this mode, use an external C/T
clock source; refer to
page 131 for more information on the external C/T clock source.
One way to perform a frequency measurement is to use the same wiring as an event counting
application that does not use an external gate signal, as shown in
Figure 67 .
Figure 67: Connecting Frequency Measurement Signals without
an External Gate Input (Shown for Clock Input 0)
In this configuration, use software to specify the counter/timer mode as frequency
measurement or event counting, and the duration of the Windows timer over which to
measure the frequency. (The Windows timer uses a resolution of 1 ms.) In this configuration,
frequency is determined using the following equation:
Frequency Measurement = Number of Events
Duration of the Windows Timer
If you need more accuracy than the Windows timer provides, you can connect a pulse of a
known duration (such as a one-shot output of another user counter) to the external gate input,
as shown in
Figure 68 .
TB58
Signal Source
Digital Ground
User Clock Input 0
TB83
TB108
Digital Shield
DT740 Screw
Terminal Panel