Campbell CR3000 Micrologger, Руководство оператора

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Section 5. Overview
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confuse the pulse wire with the positive power wire, or damage to the sensor or
CR3000 may result. Some switch closure sensors may require a pull-up resistor.
FIGURE 24: Pulse Input Wiring
Example — Anemometer
5.2.4 Period Averaging — Overview
Related Topics:
• Period Average Measurements — Specifications
• Period Average Measurements — Overview
(p. 76)
• Period Average Measurements — Details
(p. 418)
CR3000 SE terminals can be configured to measure period average.
Note Both pulse count and period average measurements are used to
measure frequency output sensors. Yet pulse count and period average
measurement methods are different. Pulse count measurements use
dedicated hardware — pulse count accumulators, which are always
monitoring the input signal, even when the CR3000 is between program
scans. In contrast, period average measurement instructions only monitor
the input signal during a program scan. Consequently, pulse count scans
can usually be much less frequent than period average scans. Pulse
counters may be more susceptible to low-frequency noise because they
are always "listening", whereas period averaging may filter the noise by
reason of being "asleep" most of the time. Pulse count measurements are
not appropriate for sensors that are powered off between scans, whereas
period average measurements work well since they can be placed in the
scan to execute only when the sensor is powered and transmitting the
signal.
Period average measurements use a high-frequency digital clock to
measure time differences between signal transitions, whereas pulse count
measurements simply accumulate the number of counts. As a result,
period average measurements offer much better frequency resolution per