PWS100 Present Weather Sensor - Campbell Scientific
PWS100 Present Weather Sensor - Campbell Scientific
PWS100 Present Weather Sensor - Campbell Scientific
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Section 8. Functional Description<br />
8.4 <strong>PWS100</strong> Control Unit<br />
The <strong>PWS100</strong> control unit, shown in Figure 8-5 as a block diagram, is a custom<br />
designed DSP board comprising a DSP, memory, timing circuits and analogue<br />
to digital converter.<br />
FIGURE 8-5. Block diagram of <strong>PWS100</strong> control unit<br />
The DSP board controls all of the functions of the system, including switching<br />
of heaters when the temperature sensors in each head pass certain thresholds,<br />
laser modulation, signal analysis and communications. The on board memory<br />
holds the program code, data tables and data for statistical manipulation.<br />
8.5 Measurement Signal Processing<br />
The <strong>PWS100</strong> has two phases of operation based around a ten second cycle. The<br />
main phase is run for nine seconds out of every ten during which it<br />
continuously captures data from the optical detectors and processes the data to<br />
analyze for particles. The second phase, which runs in the remaining second is<br />
used for making measurements from other sensors both within the sensor itself<br />
and from the external sensors. Precipitation amounts and rates are corrected<br />
for the 90% particle duty cycle, whilst counts of particles are not. As a result of<br />
this ten second cycle statistical data are only updated every ten seconds.<br />
The algorithm descriptions in this user guide give details as to how particles<br />
are detected and used to give certain output relevant to present weather<br />
monitoring.<br />
8-5