PWS100Present Weather Sensor

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1. How can a copy of the PWS100 Present Weather Viewing Software be obtained?

   The Present Weather Viewer is available for download from the Downloads section of the PWS100 product page.

2. Is there a calibration procedure for the PWS100?

   Yes. For in-situ calibration by the user, usethePWC100(Calibrator for PWS100). There is a separatePWC100 instruction manual.

3. What is the current drain of the PWS100?

   The basic processing current of the PWS100 is <200 mA at 12 V supply. However, the sensor has two levels of heating available. One set of heaters—known as the dew heaters—prevents condensation on the main lenses of the sensor. When these sensors turn on, the current usage increases to approximately 500 mA at 12 V. A current drain of 1 A is the worst case scenario if the input supply to the sensor drops to the minimum of approximately 9 V (the current drain increasing at lower voltages).

   By default, the dew heaters turn on all the time and the main hood heaters are off. The dew heaters can be turned off by the user.

   The main hood heaters run from a separate power supply and consume 7 A at 24 V when fully on. The main hood heaters only need to be used when icing conditions are likely.

4. Can a PWS100 be used to measure visibility? If so, can it be used in a sandy area such as the Sahara Desert?

   The PWS100 measures visibility by the amount of light that scatters off the particles in the sensing volume, and thus, it cannot measure visibility reduction because of absorption. However, because reduction of visibility by airborne particles is dominated by the scattering effect, the PWS100 is able to measure reduced visibility because of sand, dust, and smoke. The value, however, is less accurate and reads slightly higher for blowing dust, sand, or smoke than for precipitation.

5. At a consistently windy site, is a PWS100 less accurate than a tipping bucket rain gage?

   Unless the rain gage is poorly sited, the PWS100, similar to most sensors of this type, is less accurate measuring precipitation accumulation than a conventional rain gage.

   The PWS100, because of its high sensitivity, is more accurate at detecting the start, end, and totals of very fine rainfall events. In addition, the PWS100 does not experience the evaporation issues that a rain gage does.

6. What does the Present Weather Viewing Software do? For example, can it save data?

   The Present Weather Viewer does not have a save function for the data. The software is designed as a tool to view current data coming from the fields included in the default message of the PWS100. The Present Weather Viewer can also be used to configure the sensor and access the built-in menu system.

   To read, store, and collect data, connect the PWS100 to one of the data loggers or query the sensor directly.

7. How is the PWS100 different from a rain gage or snow depth sensor?

   The PWS100 measures the size and velocity of particles in the air. It can provide precipitation rate and water equivalent accumulation, but it is primarily used to report present weather codes, as defined by the World Meteorological Organization and National Weather Service, and particle size and velocity distributions. The PWS100 cannot measure snow depth, as it identifies water droplets in air.