Measurement Computing Data Translation DT3010 Series, Руководство пользователя, Страница: 139 / 232

Chapter 6
138
Figure 68: Connecting Frequency Measurement Signals
(Shown for Clock Input 0 and External Gate 0)
In this configuration, use software to set up the counter/timers as follows:
1. Set up one of the counter/timers for one-shot mode, specifying the clock source, clock
frequency, gate type, and type of output pulse (high or low).
2. Set up the counter/timer that will measure the frequency for event counting mode,
specifying the clock source to count, and the gate type (this should match the pulse output
type of the counter/timer set up for one-shot mode).
3. Start both counters (events are not counted until the active period of the one-shot pulse is
generated).
4. Read the number of events counted. (Allow enough time to ensure that the active period
of the one-shot occurred and that events have been counted.)
5. Determine the measurement period using the following equation:
Measurement period = 1 * Active Pulse Width
Clock
Frequency
6. Determine the frequency of the clock input signal using the following equation:
Frequency Measurement = Number of Events
Measurement
Period
Figure 69 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).
DT740 Screw
Terminal Panel
TB58
Signal Source
Digital Ground
User Clock Input 0
TB83
TB61
TB60
Gate 0
TB63
User
Counter
Output 1