CR200/CR200X Series Dataloggers - Campbell Scientific
CR200/CR200X Series Dataloggers - Campbell Scientific
CR200/CR200X Series Dataloggers - Campbell Scientific
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Section 4. Sensor Support<br />
Note: The PulseCount () instruction should not be used in a conditional<br />
statement or subroutine. To ensure all pulses are detected, it must be executed<br />
each scan.<br />
Execution of PulseCount () within a scan involves determining the accumulated<br />
counts in each dedicated 16-bit counter since execution of the last PulseCount<br />
(). PulseCount () parameter (POption) determines if the output is in counts<br />
(POption = 0) or frequency (POption = 1). Counts are the preferred output<br />
option for measuring number of tips from a tipping bucket rain gage, or the<br />
number of times a door opens. Many pulse sensors, such as anemometers and<br />
flow meters, are calibrated in terms of frequency (Hz or counts / second), and<br />
are usually measured with the frequency option.<br />
Resolution of the pulse counters is one count. Resolution of frequency is<br />
(1/scan interval). For example, the frequency resolution of PulseCount()<br />
returning a result every 1 second is 1 Hz. The resultant measurement will<br />
bounce around by the resolution. For example, if you are scanning a 2.5 Hz<br />
input once a second, in some intervals there will be 2 counts and in some 3. If<br />
the pulse measurement is averaged, the correct value will be the result.<br />
Accuracy is limited by a small scan interval error of ±(3 ppm of scan interval +<br />
10 µs) plus the measurement resolution error of ± 1 Hz. The sum is essentially ±<br />
1 Hz. Extending a 1 second measurement interval to 10 seconds, either by<br />
increasing the scan interval or by averaging, improves the resulting frequency<br />
resolution from 1 Hz to 0.1 Hz. Averaging can be accomplished by the Average<br />
() instruction or by computing a running or spatial average through<br />
programming.<br />
4.4.1 Pulse input Channels<br />
Read More! Review pulse counter specifications p. 35. Review pulse counter<br />
programming in CRBASIC Help for the PulseCount () instruction.<br />
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